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DIDEROT'S EARLY
PHILOSOPHICAL WORKS

Frontispiece.

The Open Court Series of Classics of Science and
Philosophy^ 2{o. 4

DIDEROT'S EARLY
PHILOSOPHICAL WORKS

TRANSLATED AND EDITED BY

MARGARET JOURDAIN

CHICAGO AND LONDON

THE OPEN COURT PUBLISHING COMPANY

1916

z>/ Great JBr-ffazn vtyzde?- f7i&

TABLE OF CONTENTS

PAGE

INTRODUCTION ....... i

PHILOSOPHIC THOUGHTS 27

LETTER ON THE BLIND .68

ADDITION TO THE LETTER ON THE BLIND . . 142
LETTER ON THE DEAF AND DUMB . . .158

NOTES . 219

APPENDIX . 226

INDEX ......... 245

DIDEROT'S EARLY
PHILOSOPHICAL WORKS

INTRODUCTION

DIDEROT

A COMPLETE survey of the life and works of Diderot
whom Voltaire called Pantophile is not attempted
here, for the list of the topics he handled would be
a very long one, including as it does various depart-
ments of art and science and speculation. The
Letter on the Blind (the most interesting of his
early works), however, shows him in two lights
as a free-thinker and as one of the long succession
of thinkers who prepared the way for the theory of
evolution. The agitation caused by Diderot and
his circle about the theory of transformism, it has
been said, must have largely contributed to awaken
the attention of Erasmus Darwin in England and
Lamarck in France to the necessity of throwing
more positive light on that great issue. Transformism
only needed the partial scientific confirmation which
Lamarck and Geoffroy St Hilaire gave it in the first
two decades of the nineteenth century to pass from
the realm of systematic philosophy into that of

2 DIDEROTS PHILOSOPHICAL WORKS

scientific controversy. Lamarck, who was for some
time the protege of Buffon, and in 1785 became a
contributor to the Methodic Encyclopedia' 1 (edited
by Naigeon and other friends of Diderot), eventu-
ally founded transformism when he subjected it to
definite laws. 2 Throughout the Letter on the Blind,
and indeed throughout Diderot's work, is apparent
his indebtedness to English thought ; then, and in
later life, he was the most English of Frenchmen
the man who could write to Catherine II. in 1775
that "it is obvious to all who have eyes in their
head, that if it had not been for the English, reason
and philosophy would be still in the most pitiable
and rudimentary condition in France." In Brune-
tiere's words, "There is no trace of anything but
England in the work of the man who has often been '
described as the most German of Frenchmen. " 3

Denis Diderot was born at Langres on October 5th,
1713. He was educated by the Jesuits, and threw
himself into the Bohemian life of a bookseller's hack
in Paris. His early writings were mere hackwork
a translation of Stanyan's History of Greece (1743),
for which he earned 100 crowns, and a translation
(with two collaborators) of James's Dictionary of
Medicine ( 1 746-48). The rendering of Shaftesbury 's
Inquiry concerning Virtue and Merit (1745) has
some notes of his own. Besides his volume of
stories, The Indiscreet Jewels (1748), he wrote the

* JEncycbp/die Mtthodique.

3 R. L. Cm, Diderot and English Thought, New York, 1913.

3 F. Branettere, Manuel de thistoire de la literature francaise
1898, p. 321. J * '

INTRODUCTION 3

Philosophic Thoughts and The Sceptics Walk
(1747) an allegory pointing to the extravagances
of Catholicism and the uncertainty of philosophy.
For his Letter on the Blind he was imprisoned at
Vincennes. In a second piece, published after the
Letter on the Blind, Diderot considered the case of
the deaf and dumb. The Letter on tJie Deaf and
Dumb, however, is an examination on some points
in aesthetics, not a fragment of scientific speculation
like the earlier Letter.

On his release from imprisonment at Vincennes,
at the instance of his bookseller he entered upon his
life work, the Encydop&dia. In 1745 a bookseller,
Le Breton, suggested to Diderot a book that should
be all books. In 1750 appeared d'Alembert's pre-
face, and the first volume appeared in 1751. For
years the history of Diderot and the Encyclopedia
was the same thing. ' * The thing will surely pro-
duce a great revolution in the human mind," he said
of it ; " we shall have served humanity."

Diderot, who was not equal to the task of super-
vising every department of this gigantic enterprise,
associated with himself as colleague d'Alembert, to
whom he turned for aid in the mathematical articles.
D'Alembert withdrew from the venture in 1758,
worn out with affronts and vexations of every kind ;
and for seven years the labour of carrying the vast
work to its close fell upon Diderot alone. Besides
bis labours as editor, he contributed articles on a
vast scale, so that his contributions fill more than
four of the volumes of his collected works. The

4 DIDEROT'S PHILOSOPHICAL WORKS

arguments against design would be as effective in
the mouth of the sighted. He chooses as the mouth-
piece of his scepticism the blind mathematician,
Nicholas Saunderson, and for the conversation
between that "very intelligent clergyman" Gervase
Holmes and the dying mathematician he cites as
his authority a Life of Saunderson by Dr Inchlif l
which does not exist. The transference of Diderot's
opinions to this imaginary English source of course
had its advantages in the days when "faggots
were afraid of the fire." His Saunderson resents
the clergyman's summoning as evidence of design
the magnificent spectacle of Nature. " I have been
condemned to pass my life in darkness, and yet you
cite wonders which I cannot understand, and which
are only evidence for you and for those who see as
you do. If you want to make me believe in God,
you must make me touch Him." The clergyman
replied that touch ought to be enough to reveal the
divinity to him in the admirable mechanism of his
organs. Saunderson replies that, f If this mechanism
fills you with astonishment, that is perhaps because
you are accustomed to treat as miraculous everything
that strikes you as beyond your own powers. We
think a certain phenomenon beyond human power.
We cry out at once, * 'Tis the handiwork of God ' ;
our vanity will stick at nothing less. Why can we

1 The title is "The Life and Character of Dr Nicholas Saunderson,
late Lucasian Professor of the Mathematics in the University of
Cambridge, by his disciple and friend William Inchlif esqr." Barring
the fictitious Inchlif, the date and the place, all is transcribed from the
title-Daene of the Eltm/mtx of Alsrpbra.

INTRODUCTION 5

Sunday of 1746. They were ordered by the
Parliament of Paris to be burnt, with some other
books (July 7th). The edition of 1746, however,
is not rare, and the Philosophic Thoughts were re-
printed in France, and translated into German and
Italian. They were frequently attacked and criti-
cised ; among the hostile critiques being : Pensees
philosophiques et pensees chrttiennes mises en paral-
lele, La Haye, 1746 ; Pensees raisonnables opposees
aux Pensees philosophiques, by Formey, Berlin
(Amsterdam), 1749 ; Penstes philosophiques {fun
citoyen de Montmartre, by Senemaud, 1756 ; Pensees
philosophiques sur divers sujets, La Haye, 1761 ;
and Lettres sur Vecrit intitute Pensees philosophiques
et sur le livre des Mceurs, 1749.

Diderot's little book was among those found in
the possession of La Barre.

In the Philosophic Thoughts Diderot still figures
as a Deist, opposing his God to the God of Pietists
and reading a lessoti to the atheist (Thoughts XXII
and XXIII). In Thought LVIII he proffers a con-
fession of faith in "the Roman, Catholic, and
Apostolic Church " which evidently did not disarm
his judges.

This and other references to Christianity are
" no more than ironical deference to established
prejudices" (Morley, Diderot, vol. i, p. 48). As
d'Alembert wrote of the Encyclopedia, " Time will
enable people to distinguish what we have thought
from what we have said."

In Thought XX Diderot adduces the argument

6 DIDEROTS PHILOSOPHICAL WORKS

from design as a proof of the existence of a God.
In The Sceptics Walk, however (CEuvres, i, p. 229),
his atheist puts the case against design as a proof of
the existence of God very trenchantly, and in the
Letter on the Blind (ibid., p. 311) Saunderson also
makes an eloquent protest against the inadequacy of
this proof.

THE LETTER ON THE BLIND

~" The Letter on the Blind is described in the Encyclo-
pedia x as a very subtle metaphysical work, contain-
ing certain passages which may offend pious ears.
This estimate still may stand to-day. The interest
of the letter is twofold : firstly, the scientific dis-
cussion, where he treats of the theory of vision,
and of how far a modification of the senses
would involve "a modification of the ordinary
notions acquired by men who are normally en-
dowed in their capacity for sensation " ; 2 secondly,
the argument that the argument from design is
very weak evidence for both blind and sighted
men.

The Letter is, as it claims, a discursive and
familiar document rather than a scientific treatise ;
and,- written as it was to fill the purse of Madame
de Puisieux, the writer of some forgotten literary
pieces and with some pretensions to bel esprit, her
shadow often falls across its pages. Diderot broke

1 Art. Aveugle ; see Appendix I.

2 John Morley, Diderot and the Encyclopedists, London 1886
vol. i, pp. 85-86. '

INTRODUCTION 7

with this fifth-rate female scribbler in 1749, and there
is little in her later life of interest. Madame Roland
describes her as preserving in her old age the affec-
tations of the bel esprit. " I had imagined an
authoress ought to be a very respectable personage, "
she adds ; ' but the absurdities of Madame de
Puisieux gave me food for reflection." 1

For the purpose of following the argument of the
Letter^ it will be convenient to divide it into the
two sections above mentioned.

Voltaire's popularisation of the philosophy of
Newton (1738) had stimulated scientific theory and
research in France ; and in the seventh chapter of
the second part of the Elements he describes
Cheselden's operation for cataract on a blind
lad, who was for a long time after his eyes were
couched unable to distinguish objects by size,
shape, or distance. Condillac, in 1/46, devoted
a section in his Essay on the Origin of Human
Knowledge* to the problem of the vision of the
born blind ; and in 1748, when Reaumur couched
the eyes of a blind girl, Diderot, with other
men of science, wished to make a profitable use of
the experiment. Excluded from the first experi-
ment, Diderot turned his attention to personal
observation and philosophical interrogatory of blind
persons such as the man of Puisaux and (in the
appendix written in later life) of Mademoiselle
Mlanie de Salignac. Of the more famous Nicholas

s^ vol. i, p. 157.

3 Mssai sur Vorigine des coiinaissanees Aumaznes, part i, vi
(pp. 232-256 in (Euvrcs de Condillac^ 1798, vol. i).

8 DIDEROT'S PHILOSOPHICAL WORKS

Saunderson of Cambridge, Diderot only knew the
facts given to the world in the memoir prefixed to
Saunderson's Algebra.

The blind man of Puisaux interpreted sight as a
kind of touch, and, as touch only conveyed to him
the notion of relief, a mirror was to him "an
instrument which sets us in relief out of ourselves."
The eyes were ' ' an organ on which the air produces
the same effect as my stick upon my hand. " He
would have been tempted, like Mademoiselle de
Salignac, to regard the sighted as superior in in-
telligence but for the development of the senses of
hearing and touch which supplements the deficiencies
of the blind. He did not " set any high value upon
modesty ; and if it were not for the inclemency of the
air, against which clothes are a protection, he would
hardly understand their use " ; and Diderot supposes
that the blind are, as a rule, lacking in humanity, as
the visible signs of pain do not affect them. " Do
not we ourselves cease to be compassionate when
distance or the shiallness of the object produces
on us the same effect as deprivation of sight upon
the blind ? . . . Ah, madam, how different is the
morality of a blind man from ours ; and how the
morality of the deaf would differ from that of the
blind ; and if a being should have a sense more
than we have, how woefully imperfect would he find
our morality!" It is characteristic of Diderot's
alert benevolence that he threw out a hint as to the
education of the blind by a language of touch,
" whereas for want of such a language, communica-

INTRODUCTION g

tion is entirely broken between us and those who
are born deaf, dumb, and blind." 1

Diderot comes to the conclusion that l * when the
eyes of the born blind are opened for the first time
to the light he will perceive nothing at all " ; that
some time will be necessary for the eye to make
experiments itself and in its own way and without
the help of touch.

Passing from the peculiarities of the senses of
the blind, Diderot turns to the question originally
propounded by Molyneux whether a blind man,
who had learned to distinguish by touch a sphere
from a cube, would instantly identify each if he
received sight ? Molyneux answered this question
in the negative, and Locke (who expressed agree-
ment with his solution and admiration for Moly-
neux' insight) was of opinion that the blind man
would not distinguish these objects until he had
identified by touch the source of his tactual im-
pression a conclusion in harmony with modern
doctrine. 2

Though in these speculations Diderot keeps
strictly to the problem of blindness and its effects
upon the intellect of the blind, his strongest

1 Girolamo Cardano, a sixteenth- century physician, conceived the idea
that the blind could be taught to read and write by means of touch.
About 1517 Francesco Lucas in Spain, and Rampazetto in Italy, made
use of large letters cut in wood for instructing the blind. In 1767
Jacques Bernoulli, the Swiss savant, taught a blind girl to read, but the
means of her instruction were not made known.

2 "This is in harmony with the modern doctrine that there is an
inherited aptitude of structure (in the eye, for instance), but that
experience is an essential condition to the development and perfecting
of this aptitude.' 7 Morley, Diderot and the Encyclopedists >, vol. i,
p. 90, note.

io DIDEROT'S PHILOSOPHICAL WORKS

arguments against design would be as effective in
the mouth of the sighted. He chooses as the mouth-
piece of his scepticism the blind mathematician,
Nicholas Saunderson, and for the conversation
between that "very intelligent clergyman" Gervase
Holmes and the dying mathematician he cites as
his authority a Life of Saunderson by Dr Inchlif l
which does not exist. The transference of Diderot's
opinions to this imaginary English source of course
had its advantages in the days when "faggots
were afraid of the fire." His Saunderson resents
the clergyman's summoning as evidence of design
the magnificent spectacle of Nature. " I have been
condemned to pass my life in darkness, and yet you
cite wonders which I cannot understand, and which
are only evidence for you and for those who see as
you do. If you want to make me believe in God,
you must make me touch Him." The clergyman
replied that touch ought to be enough to reveal the
divinity to him in the admirable mechanism of his
organs. Saunderson replies that, f If this mechanism
fills you with astonishment, that is perhaps because
you are accustomed to treat as miraculous everything
that strikes you as beyond your own powers. We
think a certain phenomenon beyond human power.
We cry out at once, * 'Tis the handiwork of God ' ;
our vanity will stick at nothing less. Why can we

1 The title is "The Life and Character of Dr Nicholas Saunderson,
late Lucasian Professor of the Mathematics in the University of
Cambridge, by his disciple and friend William Inchlif esqr." Barring
the fictitious Inchlif, the date and the place, all is transcribed from the
title-Daene of the Rhmtnts of Alsrpbra.

INTRODUCTION 11

not season our talk with a little less pride and
a little more philosophy ? If Nature offers us a
knotty problem, let us leave it for what it is,
without calling In to cut it the hand of a Being who
then immediately becomes a new knot, and harder
to untie than the first."

The clergyman falls back upon the evidence of
Newton, Clarke, and Leibniz. Saunderson says that,
though Newton and others may be convinced of the
admirable order of the present state of the universe,
they must leave him freedom of opinion as to its
earlier state where Holmes can confront him with
no witnesses and eyes are useless. "If we went
back (he continues) to the origin of things and
scenes and perceived matter in motion and the
evolution from chaos, we should meet with a
number of shapeless creatures instead of a few
creatures highly organised. I make no criticism
on the present state of things, but I can ask you
some questions as to the past. For instance, I may
ask you, and Leibniz, Clarke and Newton, who
told you that in the first instances of the formation
of animals some were not headless or footless ? I
may maintain that such an one had no stomach
and another no intestines ; that some who seemed
to promise a long duration from their possession of
a stomach, palate, and teeth carne to an end owing
to some defect of the heart or lungs ; that monsters
mutually destroyed one another ; that all the
defective combinations of matter disappeared, and
that only those survived whose mechanism was not

12 DIDEROTS PHILOSOPHICAL WORKS

deficient in any important particular, and who were
able to support and perpetuate themselves. "

In 1754 he was led to the same question in his
Thoughts on the Interpretation of Nature^ "Just
as in the animal and vegetable kingdoms an
individual begins, increases, endures, decays, and
passes away, might it not be the same for species
as a -whole ? If we were not taught by our faith
that animals came out of the Creator's hands as we
see them, and if it were permitted to entertain the
least doubt about their beginning and their end,
might not the philosopher, left to his own thoughts,
suspect that animality had its elements from all
eternity mixed up and dispersed in the mass of
matter; that these elements happen to encounter
one another, because it was possible that it should
happen ; that the embryo, formed of these elements,
went through an infinite series of organisms and
developments ; that in succession it acquired motion,
sensations, ideas, thought, reflection, consciousness,
sentiments, passions, signs, gestures, sounds,
articulation, a language, laws, sciences, and arts ;
that millions of years passed between each of these
stages ; that it may perhaps undergo further develop-
ments, may receive further additions which are
unknown to us ; that it has had and will have a
stationary state ; that it is receding or will recede
from that state through an immensely long decay,
during which its faculties will disappear from it as
they had come ; that it will vanish from nature for

1 2, 57-58-

INTRODUCTION 13

ever, or rather, that it will still exist in nature, but
in a form and with faculties very different from those
that we observe in it at this instant of duration?
Religion saves us many wanderings and much toil."
Continuing the conversation, Saunderson adds :
" I conjecture, then, that in the beginning when
matter in a state of ferment brought this world into
being, creatures like myself were of very common
occurrence. But might not worlds be in the same
case ? How many faulty or incomplete worlds have
been dispersed and perhaps formed again, and are
dispersed at every instant in distant regions of space
which I cannot touch nor you behold, but where
motion continues, and will continue, to combine
masses of matter, until they have found some ar-
rangement in which they may finally persevere?
O philosopher, travel with me to the limits of this
universe, beyond the point where I feel, and you
behold, organised beings, cast your eyes over this
new ocean and search in its lawless, aimless agitations
for vestiges of that intelligent Being whose wisdom
fills you with such wonder and admiration here ! "
The imaginary Saunderson becomes excited with
this prolonged debate, and after an attack of delirium
dies with the words <c O God of Clarke and Newton,
have mercy upon me ! " on his lips, and there is an
end of what the writer of the article Aveugle in the
Encyclopaedia calls a pleasantry a pleasantry by
no means to the taste of the Royal Society. The
Letter remains an effective statement of the relativity
of the idea of design. It is the vigorous present-

H DIDEROTS PHILOSOPHICAL WORKS

ment of this argument that is the strongest point of
the Letter, not the temporary position of Saunderson
who replies that he could only admit a God on
condition that he could touch Him. 1 Voltaire and
other critics have fixed on this temporary position
of Saunderson's for attack. ff l must confess,"
writes the former, "that I do not agree with
Saunderson who denied God because he happened
to be born blind. Perhaps I am mistaken, but I
should in his place have recognised a highly in-
telligent Being who had given me so many sub-
stitutes for vision ; and inferred a skilful detfniurgus
from the ordered relations of the universe by
thought." 2

Diderot gives the measure of the argument from
design in a lighter vein elsewhere. "This marvel-
lous order and these wonderful adaptations, what
am I to think of them ? They are metaphysical
entities only existing in your own mind. You
cover a vast piece of ground with a mass of ruins
falling hither and thither at hazard ; and there the
worm and the ant find commodious shelter enough.
What would you say of these insects, if they were
to take for real and final entities the relations of the
places which they inhabit to their organisation, and
then fall into ecstasies over the beauty of their
subterranean architecture, and the wonderfully
superior intelligence of the gardener who arranges
everything so conveniently for them ? " s The idea

1 J. Morley, Didcro^ vol. i, p. 97. 2 Corrcspondanct, June 1749.
3 Diderot to Voltaire, 1749. (Ewrcs, xix, p. 421.

INTRODUCTION iS

has been worked up into many apologues and fables
since that it has fallen into the domain of familiar
things ; but it has its importance as one of the many
saps in the direction of the strongly entrenched
forces of Catholicism.

NICHOLAS SAUNDERSON

The Nicholas Saunderson who figures in the
Letter on the Blind is treated with respect for
historical truth as far as his life and attainments are
concerned, but, as is well known, in his dying speech
he is merely the mouthpiece of Diderot. Saunder-
son was born in January 1682 at Thurleston, in
Yorkshire, the son of an exciseman, and lost his
sight at the age of twelve months by small-pox ; so
that he can be classed among those persons blind
from birth or from early infancy, whose case Diderot
discusses. He became a good Latin, Greek, and
French scholar, and after leaving school studied
mathematics at home until 1707. He was then
brought to Cambridge by Joshua Dunn, a fellow-
Commoner of Christ's College, with whom he lodged.
With the consent of William Whiston, Lucasian
professor, he lectured to a class on the philosophy of
Newton, hydrostatics, mechanics, sound, astronomy,
and optics ; and after the expulsion of Whiston from
the professorship in 1710, Saunderson was chosen
on Tuesday, November 2Oth, 1711, as his successor,
in spite of some opposition. 1 Newton, however,
interested himself very much in the election. His

1 Reid, Diary, 1709-1720, ed. Luard lS6o.

16 DIDEROT'S PHILOSOPHICAL WORKS

inauguration speech was delivered In very elegant
Latin and cc a style truly Ciceronian." He resided
at Christ's College until 1723, when he took a house
at Cambridge. He spent seven or eight hours a day
in teaching, and some of his lectures are preserved
In MS. at the University Library. He married a
daughter of William Dickons, rector of Boxworth,
by whom he had a son and a daughter. He died of
scurvy on April I9th, 1739, and was buried at Box-
worth, where there is a monument to his memory.
There is a portrait of him, holding an armillary
sphere, in the University Library, and an engraving
by Vandergucht is prefixed to the edition of his
Algebra^ published by subscription in 1740.

Lord Chesterfield, who attended Saunderson's
lectures when at Trinity Hall, speaks of him as a
professor who had not the use of his own eyes but
taught others to use theirs. Like many other blind
persons, his sense of touch and his hearing were
extremely delicate. "He could judge of the size
of a room Into which he was introduced by the
distance he was from the wall : and if ever he had
walked over a pavement in courts, piazzas, etc.,
which reflected a sound, and was afterwards con-
ducted thither again, he could exactly tell where-
abouts In the walk he was placed, merely by the
note it sounded." 1 He was a good performer on
the flute, and could distinguish to the fifth part of
a note. He distinguished, in a set of Roman

1 Memoirs of the Life and Character of Dr Nicholas Saunderson,
in Saunderson's Algebra (ed. 1740), vol. i, p. 13.

INTR OD UCTION 1 7

medals, the genuine from the false, (t though they had
been counterfeited with such exactness as to deceive a
connoisseur who had judged by the eye. " But, says
the writer of the memoir, <C I, who had not that
sense to trust to, 1 could easily feel a roughness on
the new cast, sufficient -to distinguish them by."

Saunderson, who became a Fellow of the Royal
Society in 1719, and was acquainted with de Moivre,
Machin, and Keill, was a devout Newtonian. His
Algebra, prepared during the last six years of his
life, was published in 1740 by his widow and daughter.
Some of his manuscripts were printed in 1751, with
the title The Method of Fluxions applied to a Select
Number of Useful Problems, together with the
Demonstration of Mr Cotes^s forms of Fluents in
the second part of his Logometria^ the Analysis of the
Problems in his Scholium Generale^ and an Explana-
tion of the Principal Proportions of Sir Isaac Newton's
Philosophy. Select Parts of Professor Saunderson } s
Elements of Algebra for Students at the. Universities
was published in 1761.

There seem to have been some grounds for
Diderot's choice of Saunderson as a mouthpiece for
his eighteenth-century illumination. Some criticism,
in a very different tone from the Memoir prefixed
to his life, appears as an article in the Biographia
Britannica* signed P. "He was supposed not
to entertain any great notion of revealed religion "
(writes P.), cc yet we are told he appointed to receive

1 Memoirs of the Life and Character of Dr Nicholas Saunderson, in
Saunderson's Algebra (ed. 1740), vol. i, p. 12.

2 Vol. vi, part ii (1766), PP- *5%-*S9-

i8 DIDEROTS PHILOSOPHICAL WORKS

the sacrament the evening before his death. " Further
details of his character added by P. are not quite in
keeping with Diderot's ideal Saunderson. * ' As to
his character," we are told, cc it is well observed that
he was a man rather to be admired than loved. He
had, indeed, much wit and vivacity in conversation,
so that none could be a better companion ; but like
his predecessor Mr Whiston, he uttered his senti-
ments of men not only freely but licentiously, with
a kind of contempt and disregard for decency and
commonsense ; and which is worse, he indulged
himself in women, wine, and profane swearing to a
shocking excess ; by which means he did more hurt
to the reputation of the mathematics than he did
good by his eminent skill in the science." The
Encyclopedia* admits the account of his dying
moments to be entirely false (absolument supposte),
and that it was considered as a crime against learn-
ing (un crime de lese-erudition). In the account in
the Memoir" we read that he was informed by
Mr Gervase Holmes that there was no hope of his
recovery. " He received this notice of his approach-
ing death with great calmness and serenity ; and
after a short silence resumed life and spirits, and
talked with as much composure of mind as he had
done In his most sedate hours of perfect health.
He appointed the evening of the following day to
receive the sacrament with Mr Holmes ; but before
that came he was seized with a delirium, which
continued to his death."

1 Art. Aveugle. 2 P. xix.

INTRODUCTION 19

In the Letter of Mr Gervase Holmes o the
Author of the Letter on the Blind^ containing the
true account of the last hours of Saounderson (sic),
a little volume printed at Cambridge, 1750, the
author finds Diderot's Letter "ingenious/' and he
adds, < I wish I could say judicious. 17 He then
proceeds to give the history of the last moments of
Saunderson, and after having denied the possibility
of Saunderson in his last moments pronouncing the
long discourse Diderot attributes to him, he puts
another, and a much longer one, in his mouth, which
is diametrically opposed to it The book, dated
14/25 December 1749, is quoted in a note on the
edition of Diderot in twenty volumes by MM. Assezat
and Tourneaux, but no copy of it is to be found in
the British Museum, the Bodleian Library, or the
University Library at Cambridge.

THE DATE OF THE LETTER

Diderot attached himself to Madame de Puisieux
in 1745, and his passion for her lasted until he dis-
covered her infidelity in I749. 1 She was needy, and
when Diderot received fifty louis for the Essay on
Merit and Virtue* he gave them to her. Shortly
afterwards she was again in need of money, and
he gave her the fifty louis which he had received

1 Madame de Puisieux came to visit him when a prisoner on parole
at Vincennes. He became jealous, and, seeing her very much dressed up
one day, asked her where she was going. " To a fSte at Champigny."
' ' Alone ? " " Yes. " Diderot distrusted her, and escaped over the wall
of the park to Champigny, where he saw his mistress with a lover. He
returned to Vincennes.

2 Essai sur te mfrite et la vertu (1745).

20 DIDEROTS PHILOSOPHICAL WORKS

for his Philosophic Thoughts?- which was written,
Madame de Vandeul says, between Good Friday
and Easter Day. "The novels of Cr^billon being
then popular," she continues, cc my father talked to
Madame de Puisieux about the composition of this
libertine literature. He declared that the main
thing was to find some amusing idea as a hinge for
the whole story, and that licentious wit took the
place of taste. She defied him to write a book of
this nature, and at the end of a fortnight he brought
her The Indiscreet Jewels and fifty louis. The needs
of Madame de Puisieux induced him to publish the
Letter on the Deaf and Blind? and he attended all
the experiments which bore upon this subject.

' Monsieur de R6aumur had in his house a man 3
blind from birth, and operated on him for cataract.
The removal of the dressing for the first time was
supposed to take place before some doctors and a
few men of letters, and among them my father was
present. He hoped for an interesting and novel
investigation, as he was anxious to investigate the
effect of light for the first time upon a person to
whom it was hitherto unknown. The dressing was
removed, but the conversation of the blind man
proved conclusively that he had already seen. The
spectators were not satisfied ; some spoke indis-
creetly as the result of the others' ill-humour ; and one
person said that the first experiment had taken place

1 Pensles Philosopkiques (1746).

2 Lettre sur les Aveugles, b V usage de ceux qui votint (1749).

3 Actually a blind girl.

INTRODUCTION 21

In the presence of Madame Dupre de Saint Maur.
My father left, saying that Monsieur de Reaumur
preferred the eyes of a senseless pretty woman to
the presence of intelligent witnesses.

"This saying displeased Madame Dupr de Saint
Maur, who considered it an insult to her eyes and
her knowledge of anatomy, for she laid claim to
scientific knowledge. She egged on Monsieur
d'Argenson 1 (who found her charming), and not
many days after, on July 24th, 1749, an officer named
Rochebrune with three men visited my father at nine
o'clock in the morning, and, after thoroughly examin-
ing his study and his papers, drew from his pocket an
order to arrest him and take him to Vincennes. " 2

He was imprisoned for twenty-eight days without
seeing anyone but Monsieur Berryer, then lieutenant
of police. Monsieur Berryer advised him to address
himself to Monsieur d'Argenson, and undertook to
deliver the letter. After twenty-eight days Madame
Diderot was ordered to go to Vincennes ; and Diderot
was taken to the Chateau and informed that the king
by an excess of clemency "allowed him to be a
prisoner on parole and take exercise in the park."
The Marquis du Chatelet,the Governor, was very kind
to him, and did his best to lighten his stay. He and
Madame Diderot remained there for three months,
after which they were allowed to return home.
During his close Imprisonment he found means of
writing in an ingenious manner. He had a tooth-

1 Then Minister of War.

2 Mtmoires pourserzrir & fhistoire de la vie ei des ouvrages de Diderot*

22 DIDEROTS PHILOSOPHICAL WORKS

pick in his pocket, of which he made a pen ; he
knocked off a slate near his window, ground it to
powder, moistened it with wine, and made an ink-
pot of a broken glass. Having in his possession a
volume of Milton's Paradise Lost^ he filled the blank
leaves and spaces with reflections on his position and
notes on the poem. Always anxious to give his
fellow-men the advantage of his discoveries, he
wrote, says Naigeon, above the door of a room :
"Ink is made with slate ground to a very fine
powder and wine, and a pen of a tooth-pick."

It is possible that Madame Duprd de Saint Maur j s
instrumentality in Diderot's arrest has been too much
emphasised, for the Government was then only too
ready to proceed against one of the boldest of the
French philosophes. Assdzat * adduces as a reason
for thinking that Diderot's arrest was not solely due
to the influence of Madame Duprd de Saint Maur
the following note by the Marquis d'Argenson in his
Memoirs : -" August, 1749. There have been these
last few days a number of abb6s, savants, and in-
tellectuals arrested, and taken to the Bastille, such
as Diderot, some professors at the University,
doctors of the Sorbonne, etc. They are accused of
having written verses satirising the king, and of
having recited and made them public, of having
intrigued against the ministry, of having written
and printed works advocating deism and immorality.
This had to be suppressed as their licence had become

1 Notice Pr61iminaire to the Lettre sur les Aveugles, csuvres com-
p&tes de Diderot, ed. J. Assezat (1875), voL i, p. 278.

INTRODUCTION 23

excessive. This is my brother's doing, who shows
himself in this a great minister."

In another note, dated August 2ist in the same
year, the Marquis adds : * ' One Diderot by name,
author of The Indiscreet Jewels and The Clear-sighted
Blind Man (the Letter on the Blind)) has been inter-
rogated in his prison at Vincennes. He received
the magistrate (some say the minister) with the
boldness of fanaticism. The Interrogator said :
6 You are insolent, and you will remain here a long
time.' This Diderot, when he was arrested, had just
written an amazing book against the religion, which
is entitled The Tomb of Prejudices."*

LETTER ON THE DEAF AND DUMB

The following note is prefixed to the Letter on
the Deaf and Dumb in Assdzat's edition of Diderot : *
"Between the Letter on the Blind and the Letter
on the Deaf and Dumb Diderot had begun to
publish the Encydopcsdia, and it was during the first
period of this long and feverish toil, which was to
last thirty years, that he found time to answer the
Abbe Batteux' work, The Fine Arts reduced to a
Single Principle. The Letter is addressed to the
author whom Diderot criticises ; it show no signs
of the haste with which the notes collected as

1 Perhaps the Marquis d'Argenson means The Sceptic's Walk (La
Promenade du Sceptique\ written in 1747. Madame de Vandeul has
told us that an agent named d'Hemery seized it. The MS. passed
from the library of Monsieur Berryer, lieutenant of police, Into that of
Monsieur de Lamoignon, and then into that of Monsieur Beaujon. It

was first published in 1830. (A)
' * Vol. i, p. 345-

24 DIDEROTS PHILOSOPHICAL WORKS

material for the Encyclop&dia were put together.
Indeed, Diderot shows a great deal of tact, polite-
ness, and ingenuity in this work. "

The Letter on the Deaf and Dumb for the Use of
those who Hear and Speak, written in 1751,
touches upon one or two points in the line of
thought of the Letter on the Blind.

There has been a considerable amount of dis-
cussion about an idea which holds a prominent
place in this Letter that of a ' ' theoretical mute"
(muet de convention). Was the idea borrowed by
Condillac from Diderot ? It must be remembered
that Diderot was very intimate at this period with
Condillac, who had introduced Rousseau to him ;
and Rousseau tells us in his Confessions that the
three men dined together every week at the " Panier
fleuri." The idea might have arisen naturally in
their meetings, or the germ of it might have been
developed independently by both Diderot and
Condillac.

.Diderot expresses his idea as follows: "My
idea would be to decompose a man, so to speak,
and to examine what he derives from each of the
senses with which he is endowed. ... It would
be amusing to get together a society, each member
of which should have no more than one sense ;
there can be no doubt that they would all treat one
another as out of their wits." This was said at the
time to be the source of the statue in Condillac's
Treatise on the Sensations (1754). Condillac's
statue was organised like a man, but with each

INTR OD UCTION 2 5

sense called into being singly, at the will of an
eternal arbiter. 1 Smell, and then other senses,
are imparted to it in turn, each increasing the
statue's stock of ideas. As the Treatise on the
Sensations was published three years after Diderot's
Letter on the Deaf and Dumb y Condillac was accused
of borrowing the idea, and he wrote a pamphlet z
defending himself from the charge, and asserting
that the idea of the statue was suggested to him by
a Mademoiselle de Ferrand.

" Of the part of the Letter that concerns gesture,"
writes Lord Morley, 3 "one can only say that
it appears astonishingly crude to those who
know the progress that has been made since
Diderot's time in collecting and generalising the
curious group of facts connected with gesture-
language. We can imagine the eager interest that
Diderot would have had in such curious observa-
tions as that gesture-language has something like a
definite syntax ; that it furnishes no means of dis-
tinguishing causation from sequence or simultaneity ;
that savages can understand and be understood with
ease and certainty in a deaf-and-dumb school." 4

As was his custom, Diderot contented himself
with throwing out a suggestion, and then broke
away into the entirely different field of aesthetics.

1 Morley, Diderot^ voL i, p. 106.

2 Rfyonse & utt reproche gut m*a <#/ fait sur fa projet extent^ dans le
Traitl des Sensations^ CEuvres, tome iii, p. 321. Paris, Briere, 1821.

3 Morley> Diderot^ vol. i, p. 107.

4 Tyler's Researches into the Early History of Mankind, chapters ii
and iii. Lubbock's Origin of Civilisation^ chapter ix.

THE notes accompanying this translation are signed as follows :

(1) Notes from the original edition : signed (D = Diderot).

(2) ,, Naigeon's edition ,, (N).

(3) ,, Belin's edition ,, (B).

(4) ,, Briere's edition ,, (Br).

(5) ,, Assezat's edition (A).

(6) Translator's notes ,, [ ].

PHILOSOPHIC THOUGHTS

Quis leget haec. PKRS. Sat. i. 2.

I WRITE of God ; I count on a very few readers ;
and do not hope to find many in agreement with
me. If these thoughts please nobody, they are
certainly bad, but I should count them sorry stuff
if they were to everybody's taste.

I

People are for ever declaiming against the
passions ; they attribute to them all the pains that
man endures, and forget that they are also the
source of all his pleasures. It is an ingredient in
man's constitution which cannot sufficiently be
blessed and banned. It is considered as an affront
to reason if one ventures to say a word in favour
of its rivals ; yet it is passions alone, and strong
passions, that can elevate the soul to great things.
Without them, there is no sublime, either in
morality or in achievement ; the fine arts return to
puerility, and virtue becomes a pettifogging thing.

II

Sober passions make men commonplace. If I
hang back before the enemy, when my country's

27

28 DIDEROTS PHILOSOPHICAL WORKS

safety is at stake, I am but a poor citizen. My
friendship is but self-regarding if my friend's peril
leaves me considering my own danger. If life is
dearer to me than my mistress, I am a poor lover.

Ill

Deadened passions degrade men of extraordinary
quality. Constraint annihilates the grandeur and
energy of nature. Look at that tree ; it is to the
luxury of its branches that you owe the coolness
and breadth of its shade, which you may enjoy
until winter despoils it of its leafy honours. There
is no more excellence in poetry, in painting, and
in music when superstition has wrought upon the
human temperament the effect of old age.

IV

It would be fortunate, people will say to me,
for a man to have strong passions ? Certainly, if
they are all in harmony. Establish a just harmony
among them, and you need fear no convulsions and
disorders. If hope be balanced by fear, the point
of honour by love of life, the taste for pleasure by
consideration for health, there will be no libertines,
nor rufflers, nor poltroons.

V

It is the very height of madness to propose the
ruin of the passions. A fine design, truly, in your
devotee, to torment himself like a convict in order
to desire nothing, love nothing, and feel nothing.

PHILOSOPHIC THOUGHTS 29

He would end by becoming a monster, If he were
to succeed.

VI

Can what is the object of my respect in one man
be the object of my scorn in another ? Certainly
not. Truth, independently of my caprices, should
be the rule of my judgments, and I shall not call
that quality a crime in one man which I admire
as a virtue in another. Am I to think that the
practice of self-improvement is to be restricted to
some few, when nature and religion inculcate it
on all alike ? Whence comes this monopoly ? If
Pachomius did well in separating himself from the
human race and burying himself in a wilderness,
I may follow his example, and in imitating him I
shall be equally virtuous ; and I see no reason why
a hundred others may not have the same right.
Yet it would be a strange sight to see an entire
province, dismayed at the dangers of society, dis-
persed in forests, the inhabitants living like wild
beasts to sanctify themselves, and a thousand pillars
rising above the ruins of all social affections ;
a new race of Stylites stripping themselves from
religious motives of all natural feelings, ceasing
to be men and becoming statues in order to be
true Christians.

VII

What voices, what cries, what groans! Who
has shut up in dungeons all these piteous wretches ?
What crimes have all these creatures committed?

30 DIDEROTS PHILOSOPHICAL WORKS

Some beat their breasts with stones, others lacerate
their body with iron nails, all express in their eyes
regret, pain, and death. Who condemns them to
such torments ? The God whom they have offended.
Who then is this God ? A God full of goodness.
But would a God full of goodness take pleasure in
bathing himself in tears ? Are not these fears an
insult to his kindness ? If criminals had to appease
the fury of a tyrant, what more could they do ?

VIII

These are people of whom we ought not to say
that they fear God, but that they are mortally afraid
of him.

IX

Judging from the picture they paint of the
Supreme Being, from his tendency to wrath, from
the rigour of his vengeance, from certain comparisons
of the ratio between those he abandons to perish
and those to whom he deigns to stretch out a hand,
the most upright soul would be tempted to wish
that such a being did not exist. We would be
happy enough in this world, if we were assured we
had nothing to fear in another. The thought that
a God did not exist has never terrified humanity,
but the idea that a God such as is represented exists.

X

God must be imagined as neither too kind nor too
cruel. Justice is the mean between clemency and

PHILOSOPHIC THOUGHTS 31

cruelty, just as finite penalties are the mean between
impunity and eternal punishment.

XI

I am aware that the sombre ideas of superstition
are more generally approved of than accepted ; that
there are pietists who do not think it necessary to
hate themselves in order to love God, or to live as
desperate wretches, in order to be religious ; their
devotion is a smiling one, their wisdom very human ;
but whence comes this difference in sentiment be-
tween people who prostrate themselves before the
same altars ? Can piety thus be subject to the law
of temperament ? Alas ! it must be so. Its influence
is only too apparent in the same devotee : he sees,
in accordance with its variations, a jealous or a
merciful God, and hell or heaven opening before
him ; he trembles with fear or burns with love ; it
is a fever with its hot and cold fits.

XII

Yes, I maintain that superstition is more of an
insult to God than atheism. "I would rather,"
said Plutarch, " that people thought that a Plutarch
never existed, than that they thought of Plutarch
as unjust, choleric, inconstant, jealous and revenge-
ful, and such as he would be sorry to be."

XIII

Only the deist can oppose the atheist. The
superstitious man is not so strong an opponent.

32 DIDEROTS PHILOSOPHICAL WORKS

His God is only a creature of the imagination.
Besides difficulties of a material nature, he is
exposed to those which result from the falsity
of his notions. A C and a S would have been
a thousand times more embarrassing to a Vanini
than all the Nicoles and Pascals in the world. 1

XIV

Pascal was an upright man, but he was timid and
inclined to credulity. An elegant writer and a pro-
found reasoner, he would doubtless have enlightened
the world, if Providence had not abandoned him to
people who sacrificed his talents to their own anti-
pathies. How much it is to be regretted that he
did not leave to the theologians of his day the task
of settling their own disputes ; that he did not give
himself up to the search for truth without reserve
and without fear of offending God, by using all the
intellect God had given him ! How regrettable that
he took for his masters men who were not worthy
to be his disciples ! One could say of him, as La
Mothe said of La Fontaine, that he was foolish
enough to think Arnauld, de Sacy, and Nicole
better men than himself.

XV

' * I tell you that there is no God ; that Creation
is a fiction ; that the eternity of the universe is no

P Vanini, 1585-1619, was executed at Toulouse in 1619, on the
charge of atheism. The initials C and S stand for the two English
deists, Cndworth and Shaftesbury. ]

PHILOSOPHIC THOUGHTS 53

more of a difficulty than the eternity of spirit ; that
because I do not see how motion could have caused
this universe (though it keeps it going), it is
ridiculous to solve the difficulty by supposing the
existence of a being of whom I can have no real
conception ; that if the wonders of the physical
universe show some intelligence, the confusions in
the moral order are the negations of a Providence.
I tell you if everything is the work of a God, every-
thing should be the best possible : for if everything is
not the best possible, it is impotence or malevolence
on the part of God. Therefore it is fortunate that I
am not better informed as to his existence. If it
were proved satisfactorily (and it is by no means
proved) that all evil is the source of good, that it
was for the best that Britannicus, the best of
princes, perished, and that Nero, the worst of men,
should reign, how is it possible to prove that it was
impossible to attain the same ends without using
such means ? To allow vice in order to throw
virtue into relief is a poor advantage in comparison
with its real disadvantage."

That, says the atheist, is my case ; what have
you to say to it? *' That I am a miserable wretch,
and that if I had nothing to fear from God, I should
not be disputing his existence" Let us leave such an
answer to orators ; it may be untrue ; politeness
forbids it and it has no savour of charity about it.
Because a man is mistaken in his denial of God,
should we insult him ? People only take refuge in
invective when they run short of proofs. Of two

3

34 DIDEROTS PHILOSOPHICAL WORKS

engaged in argument, it is a hundred to one that
the man in the wrong will become angry. * e You
thunder instead of answering," says Menippus to
Jupiter; "are you then in the wrong?"

XVI

One day somebody asked a man if real atheists
existed. Do. you think, he responded, that real
Christians exist?

XVII

None of the vain speculations of metaphysics
have the cogency of an argument ad hominem. In
order to convince, it is sometimes only necessary
to rouse the physical or moral instinct. The'
Pyrrhonist was convinced by a stick that he was
wrong in doubting his own existence. Cartouche,
pistol in hand, might have taught Hobbes a similar
lesson : "Your money or your life ; we are alone,
I am the stronger, and between us there is no
question of justice."

XVIII

It is not from the metaphysician that atheism
has received its most vital attack. The sublime
meditations of Malebranche and Descartes were
less calculated to shake materialism than a single
observation of Malpighi's. If this dangerous
hypothesis is tottering at the present day, it is to
experimental physics that the result is due. It is
only in the works of Newton, of Muschenbroek, of

PHILOSOPHIC THOUGHTS 35

Hartzoeker, and of Nieuwentit, that satisfactory
proofs have been found of the existence of a reign
of sovereign intelligence. Thanks to the works of
these great men, the world is no longer a God ; it
is a machine with its wheels, its cords, its pulleys,
its springs, and its weights.

XIX

The subtilties ol ontology have at best made
sceptics, and it was reserved for the knowledge
of nature to make true deists. The discovery of
germs alone has destroyed one of the most power-
ful arguments of atheism. Whether motion be
essential or accidental to matter, I am now con-
vinced that its effects are limited to developments ;
all experiments agree in proving to me that
putrefaction alone never produced any organism.
I can allow that the mechanism of the vilest insect
is not less marvellous than that of man ; and I am
not afraid of the inference that as an intestinal
agitation of molecules is able to produce the one, it
is probable that it has produced the other. If an
atheist had maintained, two hundred years ago,
that some day perhaps people would see men spring
full-formed from the bowels of the earth just as we
see a mass of insects swarm in putrefying flesh, I
would like to know what a metaphysician would
have had to say to him ? 1

1 Diderot here alludes to Redi's experiments about the generation of
insects, and in the preceding Thought he alludes to the discoveries due
to the telescope and microscope.- (A)

36 DIDEROTS PHILOSOPHICAL WORKS

XX

It was in vain that I made use of scholastic
subtilties against the atheist ; he found among his
feeble reasons one argument of some validity. " A
multitude of useless verities are proved to me
without any doubt," he said, "and the existence
of God, the reality of moral good and moral evil,
and the immortality of the soul are still problems
for me. What ! Is it less important for me to be
informed on these subjects than to be sure that the
three angles of a triangle are together equal to two
right angles ? " While like a skilful orator he made
me taste the full bitterness of this reflection, I joined
battle with him again with a question which must
have appeared singular to a man flushed with his
first success. "Are you a thinking being?" I
asked. "Can you doubt it?" he answered with
a pleased air. "Why not? What have I seen
to prove it? Sounds and movements? But the
philosopher sees the same in an animal to whom he
denies the faculty of thought ; why should I allow
you what Descartes refuses the ant? Externally,
your actions are designed to give me that impres-
sion ; I should be tempted to maintain that you do
think, but reason suspends my judgment. Between
external actions and thought my reason tells me
there is no essential connection ; it is possible that
your antagonist thinks no more than his watch ;
must one take for a thinking being the first animal
taught to speak ? Who has informed you that all

PHILOSOPHIC THOUGHTS 37

men are not so many well-trained parrots ? "
"That is very ingenious," he returned, " but it is
not by motion or sounds but by the continuity of
ideas, the connection between propositions, and the
links of the argument that one must judge if a
creature thinks. If there was a parrot which could
answer every question, I should say at once that it
was a thinking being. But what has this to do with
the existence of a God? If you were to prove to
me that the most intelligent man were perhaps but
an automaton, should I be the more disposed to
recognise an intelligent Being in nature ? " " That
is my affair," said I ; "but admit that it would be
madness not to credit your brother men with the
faculty of thought?" "Of course, but what
follows?" "It follows that if the universe but
why drag in the universe ? if a butterfly's wing
shows me proofs of an intelligence a thousand times
stronger than the proof you have that your fellow-
man thinks, it would be a thousand times more
foolish to deny that God exists than to deny that
your fellow-man thinks. I appeal to your know-
ledge, to your conscience ! Have you ever observed
in any man more intelligence, order, wisdom,
and reasonableness than in the mechanism of an
insect ? Is not the Deity as clearly apparent in the
eye of a flesh-worm as in the works of the great
Newton ? What, does the formation of the world
afford less proof of intelligence than its explana-
tion ? What a position ! " " But," you reply, ' ' I
admit the", faculty of thought in another the more

38 DIDEROTS PHILOSOPHICAL WORKS

readily as I myself think. " That is an analogy I
admit I cannot use, but against this must be set
the superiority of my proofs to yours. Is not the
intelligence of a first cause more conclusively proved
in nature by his works than the faculty of reasoning
in a philosopher by his writings? Remember, I
only adduced a butterfly's wing, a flesh-worm's eye,
when I could crush you with the weight of the
entire universe. I am greatly deceived if this proof
is not well worth the best that has ever issued
from the schools. It is by this argument, and
others equally simple, that I am convinced of the
existence of a God, and not by those tissues
of dry and metaphysical ideas which are better
calculated to give to truth an air of falsity than
to unveil it.

XXI

I open the pages of a celebrated professor 1 and
I read: ct Atheists, I concede to you that move-
ment is essential to matter ; what conclusion do
you draw from that ? That the world is the result
of a fortuitous concourse of atoms ? You might
as well tell me that Homer's Iliad or Voltaire's
Henriade is the result of a fortuitous concourse of
written characters." I should be very sorry to use
that argument to an atheist ; he would make quick
work of the comparison. According to laws of the
analysis of chances (he would say) I ought not

1 Briere in his edition says that Rivard, who was then professor of
philosophy, is here meant, but the argument which follows is a well-
known one. (A)

PHILOSOPHIC THOUGHTS 39

to be surprised that a thing happens, when it is
possible and the difficulty of the result is compen-
sated by the number of throws. There is a certain
number of throws in which I would back myself to
bring 100,000 sixes at once with 100,000 dice.
Whatever the definite number of letters with which
I am invited fortuitously to create the Iliad^ there
is a certain definite number of throws which would
make the venture advantageous to me ; indeed, my
advantage would be infinite if the number of throws
permitted me were infinite. You grant me that
matter exists from all eternity and that movement
is essential to it. In return for this concession, I
will suppose, as you do, that the world has no limits,
that the multitude of atoms is infinite, and that
this order which causes you astonishment nowhere
contradicts itself. Well, from these mutual admis-
sions there follows nothing else unless it be that the
possibility of fortuitously creating the universe is
very small but that the quantity of throws is
infinite ; that is to say, that the difficulty of the
result is more than sufficiently compensated by the
multitude of throws. Therefore, if anything ought
to be repugnant to reason, it is the supposition that
matter being in motion from all eternity, and
there being perhaps in the infinite number of pos-
sible combinations an infinite number of admirable
arrangements, none of these admirable arrange-
ments would have ensued, out of the infinite
multitude of those which matter took on succes-
sively. Therefore the mind ought to be more

40 DID E ROTS PHILOSOPHICAL WORKS

astonished at the hypothetical duration of chaos
than at the actual birth of the universe.

XXII

I divide atheists into three classes. There are
some who tell you openly there is no God, and are
convinced of this ; these are genuine atheists : there
is a fairly large number of people who do not know
what to think and would be glad to decide the
question by tossing up ; these are sceptical atheists :
and a still larger number who \vish there were no
God, and who pretend to be convinced of his non-
existence and live in harmony with this conviction ;
these are the braggadocios of the party. I detest
braggarts ; they are dishonest : I pity genuine
atheists ; all consolation is dead to them : and I
pray God for the sceptics ; they lack knowledge.

XXIII

The deist maintains the existence of God, the
immortality of the soul and its consequences ; the
sceptic has not decided on these points ; the atheist
denies them. The sceptic, therefore, has one more
motive for practising virtue than the atheist, and
less than the deist. If it were not for fear of the
laws, the natural tendency of a man's character,' and
the knowledge of the actual benefits of virtue, the
probity of the atheist would be lacking in founda-
tion, and that of the sceptic would be built upon a
"perhaps/ 7

PHILOSOPHIC THOUGHTS 41

XXIV

Scepticism does not suit everybody. It supposes
a profound and careful examination. He who
doubts because he is not acquainted with the
grounds of credibility is no better than an ignor-
amus. The true sceptic has counted and weighed
his reasons. But it is no easy matter to weigh
arguments. Which of us knows their value with
any exactness? Out of a hundred proofs of the
same truth, each one will have its partisans. Every
mind has its own telescope. An objection which is
invisible to you is a colossus to my eyes, and you
find an argument trivial that to me is crushing in its
efficacy. If we dispute about their intrinsic value,
how shall we agree upon their relative? Tell me
how many moral proofs are needed to balance a
metaphysical conclusion? Are my spectacles in
fault, or yours? If, then, it is so difficult to weigh
reasons, and if there are no questions which have
not two sides, and nearly always in equal measure,
how come we to cut knots with such rapidity ?
How do we come by this convinced and dogmatic
air? Have we not a hundred times experienced
how revolting is dogmatic presumption? "I have
been brought to detest probabilities," says the
author of the Essays?- " when they are foisted on
me as infallible ; I love words which soften and
moderate the temerity of our propositions, per-
adventure, in no wise, some people say, met /links,

e, book iii, cb. xi.

42 D IDE ROTS PHILOSOPHICAL WORKS

and the like ; and if I had to teach children I should
so train them to answer in this hesitating and un-
decided manner : ' What does that mean ? I do not
understand; maybe; is it true?' that they would
have the appearance of apprentices at sixty years of
age, rather than of doctors at ten, as at present. "

XXV

What is God ? A question we ask children, and
that philosophers have much trouble in answering.

We know the age when a child ought to learn to
read, to sing, to dance, to begin Latin or geometry.
It is only in religion that we take no account of his
capacity. He hardly hears what you say before
he is asked, "What is God?" It is at the same
moment, and from the same lips, that he learns of
' the existence of ghosts, goblins, were-wolves and
a God ! He is taught one of the most important
truths in a manner adapted to bring it into disrepute
one day before the bar of reason.. Would it be at
all surprising if, at twenty years of age, finding the
existence of God confounded in his mind with a
host of idle prejudices, he were to treat it as our
judges treat an honest fellow who has fallen into
bad company by some accident ?

XXVI

People begin to speak to us of God too soon,
and another mistake is that his presence is not
sufficiently insisted upon. Men have banished God

PHILOSOPHIC THOUGHTS 43

from their company and have hidden him in a
sanctuary ; the walls of a temple shut him in, he
has no existence beyond. Fools that you are,
break down these limitations that hamper your
ideas ; set God free ; see him everywhere, as he is
everywhere, or say that he is non-existent. If I
had a child to bring up, I would make his God his
companion in such a real sense that he would
perhaps find it less difficult to become an atheist,
than to escape his presence. Instead of confront-
ing him with a fellow-man (whom maybe he knows
to be worse than himself) I would say outright :
" God hears you and you are lying." Young people
are influenced by their senses. I would multiply
about him symbols indicating the divine presence.
If there were a gathering at my house, I would
leave a place for God, and I would accustom him to
say : * We were four God, my friend, my tutor,
and myself."

XXVII

Ignorance and incuriosity are two soft pillows,
but to find them so we must have a head as well
contrived as Montaigne's. 1

XXVIII

Vigorous minds and ardent imaginations do not
take kindly to the indolence of scepticism. They
would rather risk a choice than make none ; be
deceived than live in doubt. Whether they do not

1 " Oh, que c'est un doulx et mol chevet, et sain, que I'ignorance et
rincuriosite, & reposer une teste Hen faicte," Essais, Hv. iii, ch. xiii.

44 DIDEROT S PHILOSOPHICAL WORKS

trust their arms, or whether they fear deep waters,
we see them always clinging to branches they know
to be fragile. They would rather be caught on
these branches than abandon themselves to the
torrent. They are sure of everything, though they
have investigated nothing carefully ; they question
nothing because they have neither the patience nor
the courage. They make their way by broken
lights, and if by chance they come across the truth,
it is not by searching, but suddenly and, as it were,
by revelation. They are among the dogmatic group
what the illuminati are among the pietists. I have
seen individuals of this restless type, who could not
conceive how tranquillity of mind could be allied
with scepticism. "How can one live happily
without knowing what one is, whence one comes,
whither one goes, why we are here ? " "I make
a point of my ignorance on all these questions, and
am not distressed, " replies the sceptic coolly ; t c it
is not my fault if my reason is mute when questioned
on my state. All my life I shall live in ignorance
of what it is impossible for me to know, and be none
the worse for it. Why should I regret knowledge
which I could not attain, and which is doubtless
unnecessary to me, since I have it not? I would
as soon make myself wretched, says one of the
greatest geniuses 1 of our age, because I am not
equipped with four eyes, four feet, and two wings."

1 Voltaire.

PHILOSOPHIC THOUGHTS 45

XXIX

A search for truth should be required of one, but
not its attainment. May not a sophism affect me
as deeply as a solid proof? I am obliged to admit
the falsehood that I take to be the truth, and to
reject the truth that I take for a falsehood ; but how
am I to blame, if I am deceived from no fault of mine?
We are not rewarded in the next world for using
our intelligence in this ; ought we to be punished
for a lack of it ? To damn a man for foolish reason-
ing is to forget that he is a fool, and to treat him
as a criminal.

XXX

What is a sceptic ? A philosopher who has
questioned all he believes, and who believes what
a legitimate use of his reason and his senses has
proved to him to be true. Do you want a more
precise definition ? Make a Pyrrhonist sincere, and
you have the sceptic.

XXXI

What has never been put in question has not been
demonstrated. What people have not examined
without prepossession has never been examined
thoroughly. Scepticism is thus the first step to-
wards truth. It must be applied generally, for it
is the touchstone. If to ascertain the existence of
God the philosopher begins by questioning it, is
there any proposition which should not be so tested ?

46 DIDEROTS PHILOSOPHICAL WORKS

XXXII

Incredulity is sometimes the vice of a fool, and
credulity the defect of a man of intelligence. The
latter sees far into the immense ocean of possibilities,
the former scarcely sees anything possible but the
actual. Perhaps this is what produces the timidity
of the one, the temerity of the other.

XXXIII

It is as hazardous to believe too much as too little.
The danger of being a polytheist is neither greater
nor less than the danger of being an atheist ; now
scepticism is the only defence, in any period and in
any place, against these two opposite extremes.

XXXIV

A half-hearted scepticism is the mark of a feeble
understanding which reveals a pusillanimous reasoner
who permits himself to be alarmed by consequences,
a superstitious creature who thinks to honour God
by imposing fetters on his reason, a species of un-
believer who is afraid of unmasking himself to him-
self. For if truth has nothing to lose by examination,
as is the demi-sceptic's conviction, what does he
think in the bottom of his heart of those privileged
notions which he fears to investigate, and which are
hidden in a recess of his brain, as in a sanctuary
which he dares not approach ?

PHILOSOPHIC THOUGHTS 47

XXXV

I hear cries against impiety on every side. The
Christian is impious in Asia, the Mussulman in
Europe, the papist in London, the Calvinist in
Paris, the Jansenist at the top of the rue St
Jacques, the Molinist at the bottom of the faubourg
St M6dard. What is an impious person, then ?
Either everybody, or nobody,

XXXVI

When the pious declaim against scepticism, it
seems to me that they either do not understand
their own interest, or are inconsistent. If it is
certain that a true faith, to be embraced, and a
false faith, to be abandoned, need only be fully
known, surely it must be highly desirable that
universal doubt should spread over the surface of
the earth, and that every race should consent to
the examination of the truth of its religion. Our
missionaries would find a good half of their work
already accomplished.

XXXVII

He who does not deliberately embrace the faith
in which he has been bred can no more plume him-
self on being a Christian or a Mussulman than upon
not being born blind or lame. It is his luck, not
his merit.

XXXVIII

He who would die for a faith whose falsity he
was aware of, would be a madman. He who dies

48 DIDEROT S PHILOSOPHICAL WORKS

for a false faith, which he thinks a true one, or for
a true faith of whose truth he has not been con-
vinced by proofs, is a fanatic.

The true martyr is he who dies for a true faith,
whose truth has been clearly proved to him.

XXXI X

The true martyr waits for death, the enthusiast
rushes towards it.

XL

He who at Mecca would insult the ashes of
Mahomet, overturn his altars and disturb a mosque,
would be certainly impaled and perhaps would not
be canonised. Such zeal is not now in fashion.
Polyeucte in our days would be a madman.

XLI

The age of revelations, of prodigies, and of extra-
ordinary missions is no more. Christianity has
no longer need of this scaffolding. A man who
took it into his head to play the part of Jonah
amongst us, and rushed about the streets crying,
"In three days Paris will be no more. Parisians,
repent, cover yourselves with sackcloth and ashes,
or in three days you will perish," would be seized at
once, and taken before a judge, who would certainly
send him to the lunatic asylum. It would be no
use his saying to us, " Does God love you less than
the men of Nineveh : are you less guilty ? " No one
would waste his time in answering him, nor would

PHILOSOPHIC THOUGHTS 49

wait until the date of his prophecy expired before
treating him as a visionary.

Elijah may return from the other world when he
pleases ; men are such that it would be a miracle
indeed if he were well received in this.

XLII

When a dogma which contradicts the dominant
religion, or some event which is inconsistent with
the tranquillity of the public, is announced, even if
the mission is justified by miracles, the government
does well in dealing rigorously, and the people in
crying "Crucify." How dangerous to abandon the
people to the seductions of an impostor, or the
dreams of a visionary ! If the blood of Jesus Christ
cried for vengeance against the Jews, 'tis because in
shedding it they turned a deaf ear to Moses and the
Prophets who foretold the Messiah. If an angel
came down from heaven and supported his argu-
ments by miracles, and yet preached against the
law of Christ, Paul would call him anathema. It is
not, therefore, by miracles that a man's mission is
to be judged, but by the conformity of his doctrine
with that of the people to whom he declares himself
sent, especially when the doctrine of that people is
proved to be true.

XLIII

Every innovation in a government is to be feared.
The holiest and best of religions, even Christianity,
did not make its way without causing some dis-

4

50 DIDEROTS PHILOSOPHICAL WORK$

turbances. The first sons of the Church more thar
once exceeded the limits of the patience and modera-
tion recommended to them. Let me here quote some
fragments of an edict of the Emperor Julian which
are very characteristic of the genius of that philosophic
prince and of the humours of the zealots of that day.
" I had imagined," says Julian, "that the leaders
of the Galileans would be sensible of the difference
between my methods and those of my predecessor,
and that they would be grateful. Under his reign
they suffered exile and imprisonment and a number
of those they called heretics were put to the sword.
Under my reign the exiles were recalled, the
prisoners released, and the proscribed given again the
possession of their goods. But such is the restless-
ness and fury of this sect that since they have lost
the privilege of mutual destruction, of tormenting
those who are attached to their belief and those
who belong to the religion authorised by the laws,
they spare no effort and let pass no occasion to
stir up revolt. They are people without regard for
true piety and without respect for our ordin-
ances. . . . Yet we do not drag them to our altars,
nor do them violence. ... As to the poorer
classes, it seems that they are stirred to sedition by
their leaders, who are enraged at the limits we
have set to their powers ; for we have excluded
them from our courts of law, and they have no
longer the power to make away with wills and
supplant the legitimate heirs, and take possession
of inheritances. . . . That is why we forbid the

PHILOSOPHIC THOUGHTS 51

people to assemble factiously and to intrigue at the
homes of its seditious priests. . . . Let this edict
strengthen the hands of our magistrates who have
been more than once insulted by these insurgents,
and ran the risk of being stoned. Let them meet
peaceably at their leaders, and pray there, let them
there receive instruction and conform to their
religion ; we permit this so long as they refrain
from all sedition. If their meetings are an oppor-
tunity for revolt and faction, they and their property
will suffer, I warn them. Unbelievers, live in
peace . . . and you who have remained faithful
to the religion of your country and the gods of your
fathers, do not persecute your fellow-men, your fellow-
citizens, who are rather to be pitied for their ignorance
than blamed for their wickedness. It is by reason
and not by violence that men should be brought to
the truth. We enjoin therefore upon you all, our
faithful subjects, to leave the Galileans in peace."

Such were the sentiments of this prince who can
be accused of paganism, but not of apostasy. He
passed the early years of his life under different
masters and in different schools, and made an
unhappy choice in later life. He unfortunately
decided in favour of the faith of his ancestors and
the gods of his country.

XLIV

I am astonished that the works of this learned
Emperor have been preserved to us. They contain
passages which, though they do not affect the truth

52 DIDEROTS PHILOSOPHICAL WORKS

of Christianity, are by no means complimentary to
certain Christians of his time, and the Fathers of
the Church paid the works of their enemies the
singular attention of suppressing them. It is
apparently from his predecessors that Gregory the
Great derived the barbarous zeal against art and
letters which inflamed him. If this Pontiff had
had his way we should be in the plight of the
Mahometans, who have only the Koran to read.
What would have been the fate of the writers of
antiquity at the hands of a man who committed
solecisms from religious motives, who thought that
to observe grammatical rules was to set Jesus Christ
below Donatus, 1 and who thought himself obliged
to complete the ruins of antiquity ?

XLV

The divinity of the Holy Scriptures is not, how-
ever, so clearly apparent therein, that the authority
of the sacred historians is completely independent of
the testimony of profane authors. Where should
we be, if we had to find the finger of God in the
literary form of our Bible? What sorry stuff is
the Latin translation ! And even the originals
are not exactly masterpieces of composition. The
prophets, apostles and evangelists wrote as they
pleased. If we were permitted to regard the
history of the Jews purely as a production of the
human mind, Moses and his continuators are no
rivals of Livy, Sallust, Caesar, and Josephus, who

1 A Laiin giammarian.

PHILOSOPHIC THOUGHTS 53

are not suspected of being inspired. Is not the
Jesuit Berruyer preferred to Moses? In our
churches there are preserved pictures which we are
assured are the work of angels and of the Deity
himself. If these pictures were actually the work
of Le Sueur or Le Brun, what could I find to say
against this immemorial tradition ? Perhaps nothing
at all. But when I look at these celestial works,
and see the rules of painting violated at every
moment both in design and execution, and the truth
of art everywhere absent, since I cannot suppose
the author an ignoramus, I must accuse the tradi-
tion of falsity. I might make use of this analogy
between these pictures and Holy Writ, if I were not
well aware that it is immaterial whether their con-
tents are well or ill written. The prophets' forte
was telling the truth, not elegant composition.
The Apostles died for the truth of what they
preached and wrote, and for nothing else. But, to
return to the matter under discussion, those profane
writers should have been preserved who must have
harmonised with sacred historians, at any rate upon
facts such as the existence and miracles of Christ,
the qualities and character of Pontius Pilate, and the
deeds and martyrdom of the early Christians.

XLVI

An entire nation, you will say, witnesses to this
fact ; dare you deny it ? Yes, 1 dare, since it is
not confirmed by the authority of someone not of
your side, and I do not know whether that person

54 DIDEROTS PHILOSOPHICAL WORKS

is free from fanaticism and delusion. Moreover,
if an author of declared impartiality tells me that
a chasm opened in the midst "of a city, that the
gods when consulted about this event answered that
it would close if the most precious possession was
thrown into it, and that a brave knight leapt in
and that the oracle was fulfilled ; I should be far
less inclined to believe him than if he had simply
said that a chasm opened, and that considerable
time and labour were required to fill it. The less
probability a fact has the more does the testimony
of history lose its weight. I should make no
difficulty in believing a single honest man who
should tell me that His Majesty had just won a
complete victory over the allies ; but if all Paris
were to assure me that a dead man had come to
life again at Passy, I should not believe a word of
it. That a historian should impose upon us, or that
a whole nation should be deluded there is no
miracle in that !

XLVII

Tarquin proposed to increase the corps of
cavalry that Romulus had formed. An augur
declared all change in the army sacrilegious,
unless authorised by the gods. Angered at the
opposition of the priest and determined to make an
end of him and of an art which opposed his will,
Tarquin had him summoned to the market-place,
and said to him, "Soothsayer, is what I am think-
ing of possible? If your knowledge is what you

PHILOSOPHIC THOUGHTS 55

boast it to be, you will be able to answer me."
The augur was not embarrassed, but consulted the
birds and made answer: "Yes, Prince, what you
propose is possible." Then Tarquin, drawing a
razor from beneath his gown and taking a pebble,
said to the augur, c ( Come here and cut me this
pebble with this razor, for I thought this possible."
Navius, for this was the augur's name, turned to the
people and said composedly, c * Strike the pebble with
the razor, and may 1 be dragged to torture on the
spot if it is not immediately divided." People saw,
with surprise, the hardness of the pebble yield to the
blade ; it was divided so promptly that the razor
reached Tarquin's hand and drew blood. The
astonished people applauded, and Tarquin re-
nounced his scheme, and declared himself the
protector of augurs. The razor and the fragments
of the pebble were buried beneath an altar. A
statue was put up to the augur, which was still in
existence in the reign of Augustus, and both sacred
and profane writers bear witness to the truth of
this event, in the writings of Lactantius, Dionysius
of Halicarnassus, and Saint Augustine.

You have heard the story ; now for superstition.
c c What do you say to that ? " says the superstitious
Quintus to his brother Cicero. " You must either
admit it as a fact, or take refuge in a monstrous
Pyrrhonism, treat nations and historians as fools, and
burn their annals. Will you deny everything rather
than allow that the gods interfere in our affairs ? "

Hoc ego philosophi non arbitror testibus uti, qui

56 DIDEROTS PHILOSOPHICAL WORKS

aut casu veri aut malitia falsi fictique esse possztnt.
Argumentis et rationibus oportet ; quare quidquid ita
sit docere, non eventis^ Us prasertim quibus mihi
nonliceat y credere. . . . OmitteigiturlituumRomuli,
quern in maximo incendio negas potuisse combiiri ?
Contemne cot em Accii Navii ? Nihil debet esse in
philosophia commentitiis fabellis loci. Illud erat
p kilo sop hi totius augurii primum natitram ipsam
vide re ^ deinde inventionem^ deinde constantiam. . . .
Habent Etrusci exaratumpuerum ait ct or em discipline
sues. Nos Quern ? Acciumne Navium ? . . . Placet
igitur humanitatis expertes habere Divinitatis auc-
tores ? (Cicero, De divinat. , lib. ii, cap. Ixxx, Ixxxi).
But kings, peoples, nations, and the whole world
believe it. Quasi vere quidquam sit tarn valde
quam nihil sapere vulgare ? Aut quasi tibi ipsi in
fudicando placeat multitudo}- This is the philo-
sopher's reply. Tell me a single prodigy to which it
does not apply. The Fathers of the Church, who
doubtless found it exceedingly inconvenient to follow
Cicero's principles, have preferred to accept Tarquin's
adventure, and attribute the art of Navius to the
Devil. A very convenient invention, the Devil.

1 et I think a philosopher ought not to rely on evidence which either
by accident or design may be false or deceptive. He ought to explain
by argument and reasoning why each circumstance happens as it does,
rather than by events, especially when they are such as I am unable to
credit Let us therefore dispose of Roraulus's staff, which you say
resisted the action of the hottest fire, and make light of Navius* flint.
There should be no place in philosophy for such fabrications. A phil-
osopher ought to look into the whole matter of augury and its origin.
The Etruscans set up a boy turned up by a ploughshare as the author
of their discipline. Whom have we? Accius Navius ?" . . . "What
is commoner than the ignorance of the multitude ? Do you yourself
trust the common herd in a judicial case ? "

PHILOSOPHIC THOUGHTS 57

XL VI 1 1

Every nation has stories like this, which would
be miraculous if true ; which are never proved, but
which serve to prove everything ; which it were
impious to deny, and folly to believe.

XLIX

Romulus, struck by lightning, or murdered by the
senators, disappeared from Rome. The people and
the soldiers murmured, the orders of the state rose one
against the other, and Rome in its infancy, divided
against itself and surrounded by enemies, stood on
the edge of a precipice, when a certain Proculeius
came forward gravely, and said : " Romans, this
prince whom you regret is not dead: he has
ascended to heaven, where he sits at the right hand
of Jupiter. 'Go, 'he said to me, 'and calm your
fellow-citizens ; tell them that Romulus is with the
gods and assure them of my protection ; let them
know that the forces of their enemies shall never
prevail against them ; their destiny is to be one day
the lords of the earth. Let them hand down this
prediction from age to age, and to their most distant
posterity.' " Some circumstances favour imposture ;
and if we consider the state of things in Rome at
that time, we shall agree that Proculeius was a man
of intelligence and that he chose his time well.
He introduced into their minds a feeling which was
not without its effect in determining the future
greatness of his country. Minim est quantum illi

58 DIDEROTS PHILOSOPHICAL WORKS

vzro h&c nuntianti fidei fuerit ; quamque desiderium
Romuli apud plebem fact a fida immortalitatis ',
lenitum sit. Famam hanc admiratio viri et pavor
pr&sens nobilitavit ; deinde a paucis initio facto,
Deum, Deo natum salvere universi Romulumjubent. 1
That Is to say, the people believed in this appari-
tion ; the senators pretended to believe, and
Romulus had altars raised to him. But this was
not all. Soon it was not only to a single individual
that Romulus appeared ; he showed himself to
more than a thousand people in a single day. He
had not been struck by lightning, the senators had
not made away with him during a storm, but he had
ascended to heaven in the midst of lightnings and
thunders in the sight of the people ; and this story
became encrusted after a time with such a quantity
of additions that the thinkers of the following cen-
tury must have found them highly inconvenient.

A single proof is more conclusive to me than fifty
occurrences. Thanks to the great confidence I have
in my reason, my faith is not at the mercy of the
first juggler I meet with. Priest of Mahomet, you
may cure the lame, make the dumb speak, give
sight to the blind, cure the palsied, and raise the
dead, nay, even restore to the mutilated the limbs

1 ["It was strange how the man who announced these tidings was
believed, and how the people's longing for Romulus was appeased
when they believed in his immortality. Admiration of the hero, and
terror, added lustre to the story ; then, little by little, Romulus is
hailed as god, and the son of a god, by all."]

PHILOSOPHIC THOUGHTS 59

they have lost (a miracle hitherto unattempted), and
to your great surprise my faith will not be shaken.
Do you wish me to become your proselyte ? Then
leave these prodigies and let us reason. I trust my
judgment more than my eyes.

If the religion that you announce to me is true,
its truth can be demonstrated by unanswerable
arguments. Find these arguments. Why pursue
me with prodigies, when a syllogism serves to con-
vince me ? Do you find it easier to make a cripple
stand upright than to enlighten me ?

LI

A man lies on the ground, without feeling,
without warmth and without movement. They
turn him over and over, shake him, burn him,
and nothing stirs him. A red-hot iron does not
draw from him any sign of life. Is he dead ? No.
He is the priest of Calama, qui quando ei placebat
ad imitatas quasi lamentantis hominis voces^ ita se
auferebat a sensibus et jacebat simillimus mottuo, ut
non solum vellicantes atqite pungentes minime sentiret,
sed aliquando etiam igne uretur admoto y sine ullo
doloris sensu nisi post modum exmilnere* If certain
people had found such a case in our times, they
would have made a fine use of him ; we should have
seen a corpse revived on the ashes of one of the

1 ** Who, when he pleased, became remote from all feeling and lay
like a corpse, so that he did not feel those who pinched and pricked
him, and was even quite insensible to being burnt by fire, except for the
after effect," -t Augustine, Civit^ Dei^ lib, xiv, ch. xxiv.

60 DIDEROTS PHILOSOPHICAL WORKS

elect, and the collection of a Jansenist magistrate 1
would have included a resurrection, and the supporters
of the famous constitution 2 would perhaps have been
put to confusion.

LII .

We must admit, says the logician 3 of Port-Royal,
that Saint Augustine was right in maintaining, with
Plato, that our judgment of truth and our criterion
for discerning it belong not to the senses but to the
mind : non est veritatis judidum in sensibus. And
even the degree of certainty we can obtain through
the senses is not very extensive. There are many
things which we think we learn through their medium
and of which we have not a full assurance. When,
therefore, the evidence of the senses is inconsistent
with, or does not outweigh, the authority of reason,
we have no choice ; logically, we must decide for
reason.

LIII

A certain street 4 resounds with acclamations ;
the ashes of one of the elect 5 work more miracles

1 La V^ritt des miracles optrts par ^intercession de M. de Pdris,
dtmontrte centre df. UarchevSquc de Sens. Outrage dtdit au Roy par
M. de Montgeron. Utrecht, 1737. There was a continuation in 1741
and in 1748. (A)

2 [I.e. the constitution or Bull Unigenitus, which Louis XIV
obtained from Clement XI in 1713. It was an anti-Jansenist measure,
and was made a law of the land in 1730.]

3 Arnaud and Nicole, in their La Logique^ ou Fart depenser^ Amster-
dam, 1675. (Br)

4 The faubourg St Marcel, in which stands the Church of St M&iard.
-(A)

8 The Deacon Paris, upon whose tomb the convulsionaries came for
cures which Carre de Montgeron collected, and which the Jesuits denied
more passionately and obstinately than the philosophers. (A)

PHILOSOPHIC THOUGHTS 61

in one day than Jesus Christ during his whole life.
Men run, or are carried thither, and I follow the
multitude. I am no sooner arrived than I hear
cries of <( A miracle, a miracle!" I come nearer,
and looking about I see a little cripple * who walks
with the aid of three or four charitable persons who
hold him up ; and the people, in astonishment, cry
out on a miracle. Fools, where is the miracle?
Do you not see the rogue has but changed his
crutches? It is the same story with miracles as
with spirits. I would wager that all who have
seen spirits are afraid of them beforehand, and
that all those who saw miracles there had made
up their minds to see them.

LIV

We have a vast collection 2 of these so-called
miracles which may bid defiance to the most
determined incredulity. The author is a senator,
a serious man who made profession of a not very
intelligent materialism, but who had nothing to gain
by his conversion. 3 An eye-witness of the events

1 Cripples are of all sick folk the most readily subject to miraculous
influence, if we are to judge by the enormous number of crutches which
fill sanctuaries sacred to miraculous cures. In the text the Abbe
Becheran may be the person referred to ; bat he leaped like a carp,
a detail which Diderot does not give : or Philippe Sergent, stricken by
a total paralysis of the right leg and thigh, and by almost complete
paralysis of the right arm and hand ; affected by anchylosis of the knee ;
affected by a continual tremor in the left side ; and afflicted by imperfect
sight so that he was only able to see objects dimly, who was cured in a
single moment of all his maladies at the tomb of the Deacon Paris on
July loth, 1731. (A)

3 The collection of Montgeron referred to in note I, page 60.

3 Montgeron, who makes this confession, had^been suddenly converted
at St Medard, and his conversion is the first miracle he records. (A)

62 DIDEROTS PHILOSOPHICAL WORKS

which he relates, and which he had the opportunity
of examining without prejudice or bias, his evidence
is accompanied by that of thousands of others. All
say that they have seen> and their depositions are
as authentic as possible ; the original documents are
preserved in the public archives. What is to be
said? Simply that these miracles prove nothing,
so long as the question of his bona fides is not
decided.

LV

Every argument which is used by two opposing
factions cuts both ways. If fanaticism has its
martyrs like true religion, and if there have been
fanatics among those who died for the true faith,
we must either count up (if we can) the number of
dead of each camp, and believe ; or look for other '
grounds of credibility.

LVI

Nothing is more apt to confirm men in their
irreligion than false inducements to conversion.
Every day unbelievers are told : " Who are you
to attack a religion that men such as Paul, Tertullian,
Athanasius, Chrysostom, Augustine, Cyprian, and
a host of illustrious persons so courageoualy
defended? Doubtless you have observed some
difficulty which has escaped these great geniuses ;
show that you know more than they, or else, if you
admit that they are the wiser, submit your doubts
to their verdict." This is a frivolous argument.

PHILOSOPHIC THOUGHTS 63

The knowledge of its priests is no proof of the
truth of a religion. What faith was more absurd
than the Egyptians? And what priesthood was
more enlightened? " No, I cannot worship this
onion ; in what is it superior to other vegetables ?
I should be mad indeed to bow down before objects
destined for my nourishment ! A strange divinity,
a plant that I water, and which grows and dies in
my kitchen garden." "Silence, you wretch, your
blasphemies nil me with horror. Who are you to
argue ? Do you know more than the sacred college ?
Who are you to attack the gods, and preach wisdom
to their ministers ? Are you wiser than the oracles
that the whole world comes to question ? Whatever
your answer, I shall be amazed at your pride and
temerity ! " .Will Christians never know their
strength, and will they never abandon such unhappy
sophisms to those who have no better argument?
Omittamur ista communia qu& ex utraque parte
did possunt) quanqtiam vere ex utraque parte did
non possint.' 1 Example, prodigies and authority
may make dupes or hypocrites; reason alone can
make believers.

LVII

People agree that it is of the first importance to
employ none but solid arguments for the defence of
a faith ; yet they would gladly persecute those who
attempt to cry down bad arguments. * What, then,
is it not enough to be a Christian ? Am I also to

1 [" Let us leave all these common arguments which may be used by
either party, although really they cannot be used by either/*]

64 DIDEROTS PHILOSOPHICAL WORKS

be a Christian upon mistaken grounds ? Zealots, I
give you fair \varning, I am not a Christian because
Saint Augustine was, but because it is reason-
able to be one.

LVIII

I know the zealots well, and they are quick to
take alarm. If they once make up their minds
that this work contains something repugnant to
their ideas, I shall expect all the calumnies they
have spread about a hundred better men than
myself. If they only call me a deist and a wretch,
I shall get off lightly. They have long since
damned Descartes, Montaigne, Locke and Bayle ;
and I hope that they will damn many others. I
tell them that I do not pretend to be a better
man nor a better Christian than most of these
philosophers. I was born in the Roman, Catholic,
and Apostolic Church, and I whole-heartedly submit
to its decisions. I wish to die in the faith of my
fathers, and I respect it as far as is possible for a
man who has never held immediate intercourse with
the Deity, and has never witnessed a miracle. That
is my confession of faith, and I am persuaded that
they will find fault with it, though perhaps not a
man among them can make a better.

LIX

I have occasionally read Abbadie, Huet, 1 and
the rest. I arri sufficiently well acquainted with the

1 Abbadie, Traitl de la vtfrtitf de la religion chretienne> 1729. liuet,
Traitt philosophique de lafaiblesse de t esprit httmaine, 1723. (A)

PHILOSOPHIC THOUGHTS 65

evidences of my religion, and I admit that they are
important ; but were they a hundred times more so,
Christianity would not be demonstrated to me to
be true. Why then demand that I should believe
that there are three Persons in one God as firmly
as I believe that the three angles of a triangle are
together equal to two right angles? Every proof
ought to produce in me a certainty proportionate
to its collusiveness, and the effect of geometrical,
moral and physical proofs upon my mind must be
different, or else this distinction is a frivolous one.

LX

You offer an unbeliever a volume of writings of
which you claim to show him the divinity. But
before examining your proofs, he will be sure to
put some questions about this collection. Has it
always been the same ? Why is it less ample now
than it was some centuries ago? By what right
has this or that work been banished, which another
sect reveres ; and this or that work been preserved,
which the other has rejected? On what grounds
have you preferred this manuscript ? Who guided
you in your choice among so many varying copies,
which are a proof that these sacred authors have
not come down to you In their original purity ?
But if the ignorance of copyists or the malice of
heretics has corrupted the text, as you will have to
admit, you must restore the text to its original
condition before you prove its divinity ; for your
proofs and my faith cannot rest upon a collection

5

66 DWEROTS PHILOSOPHICAL WORKS

of mutilated documents. To whom will you entrust
this reform ? The Church. But I cannot agree to
the infallibility of the Church, until the divinity of
the Scriptures is proved. I am therefore reduced
to scepticism.

Your only answer to all these difficulties is by
the confession that the first foundations of the faith
are purely human ; that the choice between manu-
scripts, the restoration of passages, finally the
collection, has been made in accordance with the
rules of criticism. Well, I do not refuse the divinity
of the sacred books a degree of faith proportioned
to the certainty of these rules.

LXI

It was during my search for proofs that I found
difficulties. The books which contain the motives
of my belief offer at the same time inducements
to unbelief. They are arsenals from which either
party may draw weapons. 1 have seen the deist
arm himself there against the atheist ; the deist and
the atheist attack the Jew ; the atheist, the deist
and the Jew combine against the Christian ; the
Christian, the deist, the atheist and the Jew oppose
the Mussulman ; the atheist, the deist, the Jew, and
the Mussulman, and a multitude of Christian sects,
attack the Christian ; and the sceptic with his hand
against every man. I was the umpire, and held
the balance between the adversaries. It rose or
fell in sympathy with the weight thrown into the
scales. After long hesitation, the balance dipped

PHILOSOPHIC THOUGHTS 6;

in favour of the Christian, but simply by way of
reaction. I can bear witness to my own impartial-
ity. I might have made more of this surplus. I
call God to witness my sincerity.

LXII

This diversity of opinions has led the deists to
imagine an argument which is perhaps more curious
than solid. Cicero, having to prove that the Romans
were the most warlike people in the world, skilfully
extracts this admission from the lips of their rivals.
Gauls, to whom, if any, do you yield the palm in
courage? To the Romans. Parthians, after you, who
are the bravest of men ? The Romans. Africans,
whom would you fear, if you were to fear any?
The Romans. Let us, say the deists, interrogate
the religionists in a like manner. Chinese, what
religion would be the best, if yours were not the
best? Naturalism. Mussulmans, what religion
would you embrace if you abjured Mahomet?
Naturalism. Christians, what is the true religion
if it be not Christianity? Judaism. But you,
Jews, what is the true religion, if Judaism be false ?
Naturalism. Now, those, continues Cicero, to whom
the second place is unanimously awarded and who
in their turn do not cede the first place to anyone
it is those who incontestably deserve that place.

LETTER ON THE BLIND FOR THE
USE OF THOSE WHO SEE 1

Possunt nee posse videntur. sEneid, lib. v, 23. 2

IT was not more than I suspected, that the blind
girl whom Monsieur de Reaumur had couched for
cataract would not inform you of what you were
anxious to know ; but I little thought it would be
neither her fault nor yours. I have in person, and
by means of his best friends and by paying him
many compliments, applied to her benefactor, but
all in vain ; the first dressing will be removed with-
out you. Some persons of the highest distinction
have had the honour of sharing this refusal with
philosophers, and, in a word, he does not wish to
remove the veil, except in the presence of some eye-
witnesses of no great importance. If you would
know why that wonderful operator makes a secret
of experiments at which you think too great a
number of intelligent witnesses cannot be present,
my answer is, that the observations of such a cele-
brated person do not so much stand in need of
spectators, whilst making, as of hearers when made.

1 The Letter was addressed to Madame de Puisieux. (A)

2 |" The original is : Possunt quia possunt videntur "They succeed
because they think they will succeed.* 5 ]

68

THE LETTER ON THE BLIND 69

Thus, disappointed, madam, I have returned to my
original intention, and, since I was forced to go
without an experiment in which I saw little profit
would accrue to you or to me, but of which Monsieur
de Reaumur will doubtless make a much better use,
I set to work to philosophise with my friends upon
the important matter which is the object of it. How
happy should I be, if the narrative of one of our
conversations might stand instead of the spectacle
1 so rashly promised you ! The day that the
Prussian 1 operated on Simoneau's daughter for
cataract, we went to have some talk with the
Puisaux 2 man who was born blind. He is possessed
of good solid sense, is known to great numbers of
persons, understands a little chemistry, and has
attended the botanical lectures at the Jardin du Roi
with some profit to himself. His father was a
distinguished professor of philosophy at the Univer-
sity of Paris. He had private means, sufficient to
have satisfied his remaining senses, but a taste for
pleasure led him into some excesses in his youth ;
people took advantage of his weaknesses, his affairs
became embarrassed, and finally he withdrew to a
little town in the provinces, from whence he pays
a yearly visit to Paris, bringing with him liqueurs
which give great satisfaction. These, madam, are
not very philosophic details, but for that very reason
are likely to convince you that the person I am
speaking of is not imaginary.

1 Hilnier, a Prussian oculist. (Br)

2 A small town in the Gatinais. (D)

70 D IDE ROTS PHILOSOPHICAL WORKS

We arrived at our blind man's house about five
o'clock in the afternoon, and we found him busy
teaching his son to read with raised letters. He
had only been up an hour, for I must tell you the
day begins for him when it is ending for us. His
custom is to look after his household affairs and to
work while others are asleep. At midnight nothing
interrupts him, and he is in no one's way. His
first care is to set in its place everything that has
been displaced during the day, and when his wife
wakes she generally finds the house tidy. The
difficulty the blind have in finding things that are
mislaid makes them orderly, and I have observed
that their intimates also share this quality, either
from the effect of the good example of the blind, or
from a feeling of compassion towards them. How
unhappy would the blind be without the little
attentions of those about them ! nay, we ourselves
feel the want of them. Great services are like the
large gold or silver coins that we rarely make use
of, but small attentions are small change which is
always passing from hand to hand.

This blind man is a good judge of symmetry.
Symmetry, which is perhaps a matter of pure con-
vention among us, is certainly so in many respects
between a blind man and the sighted. A blind
man studies by his touch that disposition required
between the parts of a whole to enable it to be called
beautiful ; and then at length attains to a just
application of that term. But in saying "that is
beautiful," he does not form an opinion, it is no

THE LETTER ON THE BLIND 71

more than repeating the judgment of those who see ;
and is not this the case of three-fourths of those
who give their opinion on a play or a book ? Beauty
for the blind is but a word when divorced from
utility, and, wanting an organ, how many things
are there the utility of which escapes them ? Are
not the blind very much to be pitied in accounting
nothing beautiful unless it be likewise good ? How
many admirable things are lost to them ! The only
compensation for their loss is that their ideas of
beauty, though less extensive, are more definite
than those of many keen-sighted philosophers who
have written prolix treatises on the subject. This
blind man often speaks of mirrors. You think he
does not know the meaning of the word, yet he is
never known to put a glass in a wrong light He
speaks as sensibly as we on the qualities and defects
of the organ which he lacks. If he attaches no idea
to the terms he makes use of, yet he has the
advantage over most other men that he never uses
them wrongly. He speaks so wisely and so well of
so many things absolutely unknown to him, that his
conversation would considerably lessen the weight
of that inference which, without knowing wherefore,
we all draw from what passes in ourselves to what
passes within the minds of others.

I asked him what he meant by a mirror ? * c An
instrument," answered he, "which sets things in
relief at a distance from themselves, when properly
placed with regard to it. It is like my hand, which,
to feel an object, I must not put on one side of it,"

72 DIDEROTS PHILOSOPHICAL WORKS

Had Descartes been born blind, he might, I think,
have hugged himself for such a definition. Pray
consider what an ingenious combination of ideas
it implies. This blind man's only knowledge of
objects is by touch. He knows by hearing other men
say so that they know objects by sight as he knows
them by touch ; at any rate that is the only idea he
can form of the process. He also knows that we
cannot see our own face though we can touch it.
Sight, he therefore concludes, is a kind of touch
which extends to distant objects and is not applied
to our face. Touch gives him an idea only of relief.
Therefore, he concludes, a mirror is an instrument
that represents us in relief outside ourselves. How
many famous philosophers have laboured with less
subtlety to arrive at conclusions equally erroneous !
But if a mirror astonished our blind man, how much
greater was his surprise when we told him that there
are instruments which magnify objects, while others
remove them without duplicating them, put them
out of their place, bring them nearer, remove them
farther, and reveal the minutest details to the eyes
of naturalists ; while others again multiply objects
a thousand times, and others appear to change the
figure of objects completely. He asked us a hundred
curious questions concerning these phenomena. For
instance, he asked us if only persons who were called
naturalists could see with the microscope, and if
only astronomers could see with the telescope ; if
the instrument for enlarging objects were bigger
than that for diminishing them ; if that which brings

THE LETTER ON THE BLIND 73

them nearer were shorter than that for removing
them farther off. But what puzzled him was that
the other self, which according to him the mirror
represents in relief, should not be tactile.

"So this little instrument," said he, "sets two
senses to contradict one another ; a more perfect
instrument would perhaps reconcile these contradic-
tions, without the object being ever more real for
that, and perhaps a third instrument, still more
perfect and less illusory, would cause these contra-
dictions to disappear and show us our error. ""

"And what are eyes, do you suppose?" asked

Monsieur de . "An organ," replied the blind

man, Cf on which the air has the effect this stick has
on my hand." That answer amazed us, and while
we gazed at one another in astonishment he con-
tinued : ' ' When I place my hand between your
eyes and an object, my hand is present to you but
the object is absent. The same thing happens
when I reach for one thing with my stick and come
across another."

Madam, only turn to Descartes 1 Dioptrics, and
there you will see the phenomena of sight illus-
trated by those of touch, and the plates full of men
busied in seeing with sticks. Descartes, and all
the later writers, have not been able to give us
clearer ideas of vision ; and that great philosopher
was, in this respect, no more superior to the blind
man than a common man who has the use of his
eyes.

No one thought of asking him questions as to

74 DIDEROT 'S PHILOSOPHICAL WORKS

FIG. i.

The above figure is an enlarged reproduction of the cut in the
original edition of the Letter 071 the Blind. In the Discattrs de la
mttkodC) plus la dioptrique^ les mtttoreS) la mtcanisme et la musique
(Leyden, 1637), blind people trying to see with sticks are often repeated,
but these are small figures only an inch in height dressed as beggars
and accompanied by a dog. Diderot probably refers to an edition by
P. N. Poisson of this work (1724). (A)

THE LETTER ON THE BLIND 75

painting and writing, but it is obvious that his
comparison would fit in with every question, and I
make no doubt but that he would have told us that
to try to read or to see without eyes was like looking
for a pin with a thick stick. We only talked to him
about those kinds of glasses which exhibit objects in
relief, and which are both so very similar to and so
very different from mirrors ; but these we perceived
rather contradicted than coincided with his idea of a
looking-glass, and he was apt to think that a painter
might perhaps paint a looking-glass, and thus it
came to represent objects in colours.

We saw him thread very fine needles. May I ask
you, madam, to suspend your reading for a while
and try what you would do in his place ? In case
you do not light upon any expedient, I will tell you
of our blind man's. He takes the eye of the needle
transversely between his lips and in the same direc-
tion as his mouth, then by his tongue and suction
he draws in the thread, which follows his breath
unless it is much too thick for the eye ; but in that
case a man with sight is in the same difficulty as
the blind.

He has a surprising memory for sounds, and can
distinguish as many differences in voices as we can
in faces. He finds in these an infinite number of
delicate gradations which escape us because we have
not the same interest in observing them. For us,
these shades of difference are like our own counten-
ance. Of all the men we have seen, the one we
least remember is our own self. We notice faces to

76 DIDEROT'S PHILOSOPHICAL WORKS

recognise people ; and if we do not remember our
own, it is because we are never liable to mistake
ourselves for another person or another for our-
selves. Moreover, the mutual aid our senses lend
stands in the way of their perfection. This will not
be the only occasion where I shall have to remark
upon this.

On this head our blind man said : " That he
should think himself a pitiable object in wanting
those advantages which we enjoy, and that he should
have been inclined to consider us as superior beings
had he not a hundred times found us very much
inferior to him in other respects." This reflection
led to another. This blind man, we said, values
himself as much as, and perhaps more than, we
who see. Why then, if the brute reasons (and
it is scarce to be doubted), why on weighing its
advantages over man as better known to it than
those of man over it, should it not make a similar
inference ? He has arms, perhaps says the gnat, but
I have wings. He has weapons, says the lion, but
have we not claws? The elephant would look on
us as insects ; and all the animals, while allowing
us reason, with which we should at the same time
stand in great need of their instinct, would claim
that with their instinct they could do very well with-
out our reason. We have such a strong desire to
exaggerate our qualities, and make little of our
defects, that it would seem man's part to write a
treatise on force, and animals' on reason.

One of our company bethought him of asking our

THE LETTER ON THE BLIND 77

blind man if he would like to have eyes. "If it
were not for curiosity," he replied, " I would just as
soon have long arms : it seems to me my hands
would tell me more of what goes on in the moon
than your eyes or your telescopes ; and besides, eyes
cease to see sooner than hands to touch. I would
be as well off if I perfected the organ I possess, as
if 1 obtained the organ which I am deprived of."

Our blind man points with such exactness at the
place whence a noise comes that I make no doubt
the blind may, by practice, become very dexterous
and very dangerous. I will tell you a story which
will convince you how imprudent it would be to
stand the throwing of a stone or discharging of a
pistol by a blind man, were he in the least used to
that weapon. He had in his youth a quarrel with
one of his brothers, who came off badly. Provoked
at some insulting language, he seized the first missile
which came to hand, threw it at him, and hit
him directly on the forehead, so as to lay him flat
on the ground.

This, with some other occurrences of the like
kind, caused him to be brought before the police.
The outward show of power, which affects us so
strongly, is as nothing to the blind. Our blind
man appeared before the magistrate, as before an
equal; menaces did not intimidate him. "What
will you do to me?" he asked Monsieur Herault. 1
"I will commit you to a dungeon," answered the
magistrate. "Ah, sir," the blind man replied, **I

1 Lieutenant of police. (Br)

78 DIDERO'rS PHILOSOPHICAL WORKS

have been in one for twenty-five years." There was
an answer, madam ; and what a text for one who is so
fond of moralising as your humble servant ! We quit
life as we would a charming scene, the blind leave it
as a dungeon ; and if we have more pleasure in living
than he, he has less reluctance to meet his end.

The blind man of Puisaux judges of his nearness
to the fire by the degrees of heat ; of the fulness of
vessels by the sound made by liquids which he
pours into them ; of the proximity of bodies by the
action of the air on his face. He is so sensitive to
the least atmospheric change, that he can distinguish
between a street and a closed alley. He is an
extremely good judge of the weight of bodies and
the capacity of vessels ; and he has trained his arms
to be such an exact balance, his fingers to be such
skilful compasses, that in this kind of statics I
would always back our blind man l against twenty
persons with all their eyes about them. The
smooth surface of bodies has as many shades of
difference for him as the sound of voices, and there
is no risk of his mistaking his wife for another,
unless he was to be the gainer by the change. Yet
it is very probable that among a blind people wives
would be in common, or their laws against adultery
must be severe indeed, so very easy would it be for
wives to deceive their husbands by concerting a
sign with their gallants.

1 Clement (dug ann&s Htt^raires, lettre xxxiii) chooses this
passage to give his correspondent some idea of this new book of
Diderot's which he describes as obscure, and in which he only finds a
very slight exhibition of learning. (A)

THE LETTER ON THE BLIND 79

He judges of beauty by touch that is easy to
understand ; but what is not so easy to grasp is
that his judgment is influenced by pronunciation
and the sound of a voice. Anatomists ought to tell
us if there is any relation between the parts of the
mouth and the palate and the exterior conformation
of the face. He can turn small articles on the lathe,
and do needlework ; he levels with a square ; he
puts together and takes to pieces simple machines.
He is so far skilled in music as to play a piece when
he has been told the notes and their value. He
judges of the duration of time much more accurately
than we by the succession of actions and of thoughts.
A smooth skin, firm flesh, an elegant shape, sweet
breath, charm of voice and graceful pronunciation
are qualities he prizes very highly.

He married to have eyes of his own. Before
this, he had an idea of taking a deaf man as his
partner, to whom he could lend ears in exchange
for eyes. I could not sufficiently wonder at his
singular address in a great many things ; and on our
expressing our surprise, "I perceive, gentlemen,"
said he, " that you are not blind : you are astonished
at what I do, and why not as much at my speak-
ing ? " There is more philosophy, I believe, in this
answer of his than he was aware of. The facility
with which we are brought to speak is not a little
surprising. We have a number of ideas which
cannot be represented by sensible objects, and
which have no substance, as it were, and we are
obliged to find terms for them by making use of a

So DIDEROT'S PHILOSOPHICAL WORKS

number of ingenious and profound analogies observed
between them and the ideas they suggest. Thus a
blind man should find greater difficulty in learning
to speak because there is a much larger number
of imperceptible objects in his world, and thus
his field for comparing and combining is much more
limited. How, for example, can he rightly use
the word expression (of countenance)? It is the
same of many things imperceptible to the blind ;
and for us who see, it is often found hard to explain
very precisely what it is. If it largely resides in
the eye, touch will be useless ; and what does a
blind man make of dead eyes, or sparkling or
expressive eyes? I infer from thence that we
unquestionably derive great advantages from the
concurrence of our senses and our organs ; still, it
would be quite another thing did we use them
separately, and never employed two when one
would suffice. To add touch to sight, when sight
would do the business, is like putting to a carriage
with two stout horses a third, which will draw one
way while the others draw another.

As to me it has always been very clear that the
state of our organs and our senses has a great
influence on our metaphysics and our morality, and
that those ideas which seem purely intellectual are
closely dependent on the conformation of our
bodies, I put some questions to the blind man
about the virtues and vices. The first thing I
remarked was his extreme abhorrence of theft ;
possibly from two reasons firstly, the facility with

THE LETTER ON THE BLIND 81

which people could steal from him unobserved, and
secondly (and still more perhaps ), because he could
be immediately seen were he to go about filching.
Not that he is at any loss to secure himself against
that sense which he knows we have above him, or
that he is clumsy at hiding what he might steal.
Modesty he makes no great account of. If it were
not for the weather, against which clothes are a
protection, he would hardly understand their use ;
and he openly admits he cannot see why one part
of the body should be hidden rather than another ;
and still less by what caprice some of those parts
should be especially singled out, which from their
use and the indispositions to which they are subject
ought rather to be kept free. Though living in an
age when philosophy has rid us of a great number
of prejudices, I do not think we shall ever arrive at
such complete insensibility to the prerogatives of
modesty as this blind man. Diogenes would have
been no philosopher in his account.

As of all the external signs which raise our pity
and ideas of pain the blind are affected only by cries,
I have in general no high thought of their humanity.
What difference is there to a blind man between a man
making water and one bleeding in silence? Do not we
ourselves cease to be compassionate when distance or
the smallness of the objects produces on us the same
effect as deprivation of sight upon the blind ? So
much do our virtues depend on the sensations we
receive, and the degree by which we are affected by
external things. I don't doubt that if it were not

6

82 DIDEROTS PHILOSOPHICAL WORKS

for the fear of punishment, many people would find it
less disagreeable to kill a man at a distance at which
he would appear no bigger than a swallow, than to
cut an ox's throat with their own hands. We pity
a horse in pain, and we make nothing of crushing
an ant ; and is it not by the same principle that we
are moved ? Ah, madam, how different is the mor-
ality of the blind from ours ? How different would
that of a deaf man likewise be from his ? And to
one with a sense more than we have, how deficient
would our morality appear to say nothing more ?
Our metaphysics and theirs agree no better. How
many of their principles are mere absurdities to us,
and vice versd ? Concerning this I might enter into
details, which I am pretty certain would amuse you,
but which certain people, who make a crime of every-
thing, would not fail to exclaim against as profanity
and infidelity, as if it were in my power to make the
blind perceive things otherwise than they do. I will
content myself with one observation, which every-
one must allow, and that is, that the great argument
for the wonders of nature falls flat upon the blind.
The facility with which we create (if I may say so)
new objects by means of a little glass, is something
more incomprehensible to them than the stars which
they have been condemned never to see. This
luminous globe which moves from east to west sur-
prises them less than a small fire which they can
increase or diminish at will ; and as they see matter
' in a more abstract manner than we do, they are less
indisposed to believe that it thinks.

THE LETTER ON THE BLIXD 83

If a man who had had sight only for a day or
two found himself in the midst of a blind people,
he would either have to hold his peace or be con-
sidered a brain-sick fool. Every day lie would
come out with some new wonder, which would only
be such to them, and which their free-thinkers
would oppose tooth and nail. Might not the apolo-
gists of religion greatly avail themselves of such a
stubborn unbelief, which, however just in some
respects, is yet so very ill-founded ? Be pleased to
dwell only a little upon this supposition ; it will
remind you of the persecutions undergone by those
poor wretches who discovered truth in the dark ages
and were rash enough to reveal it to their blind
contemporaries, and found their bitterest enemies
were those who from their circumstances and educa-
tion would have seemed most likely to receive it
willingly.

So much for the morals and metaph\ sics of the
blind. I now pass on to less important matters,
which have nevertheless lately been the chief subject
of observation with regard to the blind ever since
the Prussian oculist's arrival. First question : How
can a man born blind form ideas of figures? By
the movements of his own body and by stretching
his hand in various directions, by passing his fingers
continuously over an object, he gets an idea oi space.
If he passes his fingers along a taut thread, he
obtains the idea of a straight line ; if he follows the
curve of a slack thread, that of a curve. In a more
general sense, by repeated usage of the sense of

84 DIDEROTS PHILOSOPHICAL WORKS

touch, he has a memory of sensations experienced
at different points ; and he is capable of combining
these sensations or points and forming figures. A
straight line for a blind man who is not a geomet-
rician is but the memory of a series of sensations
of touch upon a taut thread ; a curve, the memory
of a series of tactile sensations referred to the surface
of some concave or convex solid. In the case of a
geometrician, study corrects the idea of these lines
by their properties which he discovers. But whether
geometrician or no, the man born blind refers every-
thing to his fingers' ends. We combine coloured
points, he only palpable points, or, to speak more
precisely, only such tactile sensations as he remem-
bers. He does not go through a mental process
analogous to ours ; he does not create an image, for
to do this it is necessary to colour a background and
mark upon it points of a different colour from that
background. Make these points of the same colour
as the ground, and they are at once lost in it, and
the figure disappears ; at any rate, that is the case
in my imagination, and I suppose all imaginations
are alike. When I propose to perceive in my head
a straight line otherwise than by its properties, I
begin by spreading in it a white cloth, against which
I set out a series of black points in the like direction.
The stronger the colour of the ground and points,
the clearer my perception of the points. To view
in my imagination a figure of a colour resembling
that of the ground, puts me to no less trouble than
if out of myself and on a canvas. You see "then,

THE LETTER ON THE BUND 85

madam, that laws might be given for imagining with
ease various objects variously coloured, but such
laws are by no means calculated for one born blind.
Such a man who cannot colour (and consequently
cannot figure as we understand it) only remembers
such sensation as one derives from touch, which
he refers to different points, places and distances,
and of which he composes figures. I believe that
we who see never Imagine any shape without colour-
ing it, and that if we are given little balls in the
dark, whose substance and colour are unknown to
us, we shall immediately think of them as black or
white, or some other colour ; and that if we did not,
we, like the blind man, should have the remembrance
only of little sensations excited at our fingers* ends,
and such as little round bodies may occasion. If
this remembrance be very fleeting with us, if we
have very little idea how one born blind fixes,
recalls and combines the sensations of touch, it is
owing to the custom we derive from our eyes of
realising everything in our imagination by means of
colours. It has happened, however, that during
the agitations of a violent passion I felt a thrill
run through my whole hand, and I felt the im-
pression of the bodies I had touched some time ago
revived as vividly as if they had been still present
to my touch, and I realised very distinctly that the
limits of sensation exactly coincided with those of
these absent bodies. Although sensation by itself
is Indivisible, it occupies, if one may use the word,
an extension In space to which the blind man Is

86 DJDEROrS PHILOSOPHICAL WORKS

able to add and subtract mentally by enlarging or
diminishing the parts affected. By this means he
compares points, surfaces, and solids ; and he could
imagine a solid as large as this terrestrial globe, if
he were to imagine his fingers' ends as large as this
globe, and occupied by sensation in its , length,
breadth, and depth. I know of nothing which is
a better proof of the reality of this internal sense
than this faculty, weak in us, but strong in those
born blind, of feeling or recalling the sensation of
bodies when they are absent and no longer acting
on us. We cannot make a blind man understand
how imagination represents absent objects as present
to us, but we can easily recognise in ourselves the
faculty that the blind possess of feeling at one's
fingers' ends an absent body. To do this, press
the forefinger and thumb together, shut your eyes ;
separate your fingers, and immediately after this
separation examine yourself and tell me if the
sensation does not linger after the pressure has
ceased ; if, while the pressure lasted, your mind
appears to be in your head rather than at the ends
of your fingers, and if this pressure does not convey
the nature of a surface by the space which the
sensation occupies? We only distinguish the
presence of external things from their picture in
our imagination by the strength or weakness of, the
impression ; and similarly, the blind only distinguish
the sensation from the actual presence of an object
at their fingers' ends, by the strength or weakness
of that sensation.

THE LETTER ON THE BLIND 8;

If ever a philosopher, blind and deaf from his
birth, were to construct a man after the fashion
of Descartes, I can assure you, madam, that he
would put the seat of the soul at the fingers' ends,
for thence the greater part of the sensations and all
his knowledge are derived. Who is to inform him
that his head is the seat of his thoughts? If the
labours of the imagination tire our brain, this is
because the effort we make to imagine is somewhat
similar to that to perceive very near or very small
objects. But this would not be the case with a man
blind and deaf from his birth, for the sensations
which he has gathered from touch will be the world,
so to speak, of all his ideas, and I should not be
surprised if, after a profound meditation, his fingers
were as wearied as our heads. I am not afraid that
a philosopher might object to such an one that the
nerves cause our sensations and that they all start
from the brain. Were these two propositions fully
demonstrated, which is very far from being the case,
especially the former, an exposition of all the dreams
of naturalists on this head would be sufficient to
confirm him in his opinion.

But if the imagination of the blind mac be no
more than the faculty of calling to mind and com-
bining sensations of palpable points ; and of a sighted
man, the faculty of combining and calling to mind
visible or coloured points, the person born blind
consequently perceives things in a much more
abstract manner than we ; and in questions purely
speculative, he is perhaps less liable to be deceived.

88 DIDEROTS PHILOSOPHICAL WORKS

For abstraction consists in separating in thought
the perceptible qualities of a body, either from one
another, or from the body itself in which they are
inherent ; and error arises where this separation is
done in a wrong way or at a wrong time in a wrong
way in metaphysical questions, or at a wrong time
in applied mathematics. There is perhaps one certain
method of falling into error in metaphysics, and that
is, not sufficiently to simplify the subject under in-
vestigation ; and an infallible secret for obtaining
incorrect results in applied mathematics is to suppose
objects less compounded than they usually are.

There is one kind of abstraction of which so few
are capable that it seems reserved for purely intel-
lectual beings, and that is that by which everything
would be reduced to numerical units. We must
admit that the results of this geometry would be
very exact, and its formulas very comprehensive,
for there are no objects, either possible or actually
existent, which these simple units could not represent,
by points, lines, surfaces, solids, thoughts, ideas,
sensations, etc. ; and if this should prove to be the
foundation of Pythagoras's doctrine, he might be
said to have failed in his aim, his mode of philoso-
phising being too much above us, and too near that
of the Supreme Being, who, according to the in-
genious phrase of an English geometrician, 1 always
geomet rises in the universe.

1 [Briere gives the name of this geometrician as Rapson (sic}. Raphson,
not a very distinguished mathematician, may, among many others, have
quoted this doctrine of Plato, but it is not very important if he did so.
What makes the dictum important in Plato's mouth is that he had a

THE LETTER ON THE BLIND 89

But units pure and simple are too vague and
general symbols for us. Our senses bring us back
to symbols more suited to our comprehension and
the conformation of our organs. We have arranged
that these signs should be common property and
serve, as it were, for the staple in the exchange
of our ideas. We have made them for our eyes in
the alphabet, and for our ears in articulate sounds ;
but we have none for the sense of touch, although
there is a way of speaking to this sense and of
obtaining its responses. For lack of this language,
there is no communication between us and those
born deaf, blind, and mute. They grow, but they
remain in a condition of mental imbecility. Perhaps
they would have ideas, if we were to communicate
with them in a definite and uniform manner from
their infancy ; for instance, if we were to trace on
their hands the same letters we trace on paper, and
associated always the same meaning with them.

Is not this language, madam, as good as another?
Is it not ready to hand, and would you dare to say
that you have never been communicated with by
this method ? Nothing remains but to fix it, and
make its grammar and dictionaries, if it is found
that the expression by the common characters of
writing is too slow for the sense of touch. Know-
ledge has three entrances by which it reaches our

theory that geometry is more fundamental and comprehensive than
arithmetic. He disagreed in this respect from the Pythagoreans because
he clearly realised that there were certain lengths of lines expressible
geometrically but not arithmetically ; cf. Brunschvicg, Lts Mopes de fa
philosophie mathtmatiqtte, pp. 45. 47 4&]

90 DTDRROTS PHILOSOPHICAL WORKS

mind, and we keep one barricaded for want of signs.
If the two others had been neglected we should now
be little better than beasts. Just as a pressure Is
the only sign we have to the touch, so a cry would
have been the only sign to the hearing. We have
to lose one sense before we realise the advantage of
symbols given to the remainder, and people who
have the misfortune to be born deaf, blind, and mute,
or who have lost these three senses by some accident,
would be delighted if there existed a clear and
precise language of touch.

It is much easier to use symbols already invented
than to invent them, as one is obliged to do when
there are none current. What an advantage it would
have been for Saunderson to find an arithmetic
arranged with signs for the touch all ready to hand
at the age of five, instead of having to invent it at
twenty-five ! This Saunderson, madam, is another
blind man whose story you will be interested to
hear. Wonderful stories, indeed, are told of him,
and yet there is not one to which, from his attain-
ments in literature and his skill in mathematics, we
may not safely give credit. He used the same
machine for algebraical calculations and for the
description of rectilinear figures. 1 You would be
interested in an account of this if intelligible, and
you will see my description assumes no more know-
ledge on your part than you actually possess, and
that it would be very useful to you if you should
ever want to make long calculations by touch.
1 See note I, p. 219.

THE LETTER OX THE BLIND g\

Imagine a square such as you see in figures 2 and
3, divided into four equal parts by lines perpendicular
to the sides, in such a way that it gives nine points,
I, 2, 3, 4, 5, 6, ;, 8, 9. Suppose this square per-
forated with nine holes to hold pins of two kinds,
both of the same length and thickness, but one kind
with a head larger than that of the other.

The large-headed pins are only placed in the centre
of the square, the small-headed pins only on the
sides, except in the single case of zero. Zero is
marked by a large-headed pin placed in the centre
of the small square which has no pin set on the sides.
The figure I is represented by a small-headed pin,
placed in the centre of the square, which has no pin
set on its sides. The figure 2, by a large-headed pin
placed in the centre of the square, and by a small-
headed pin placed in one of the sides at the point
I. The figure 3, by a large-headed pin placed in
the centre of the square, and by a small-headed pin
placed in one of its sides at the point 2. The figure
4, by a large-headed pin placed in the centre of the
square, and by a small-headed pin placed in -one of
the sides at the point 3. The figure 5, by a large-
headed pin placed in the centre of the square, and by
a small-headed pin placed in one of the sides at the
point 4. The figure 6, by a large-headed pin placed
in the centre of the square, and by a small-headed pin
placed in one of its sides at the point 5. The figure
7, by a large-headed pin placed in the centre of the
square, and by a small-headed pin placed in one of
the sides at the point 6. The figure 8, by a large-

92 DIDEROTS PHILOSOPHICAL WORKS

headed pin placed In the centre of the square, and
by a small-headed pin placed in one of the sides
at the point 7. The figure 9, by a large-headed

...J

d

FIG. 2.

'/

FIG. 3.

pin placed in the centre of the square, and by a
small-headed pin placed in one of the sides at
the point 8.

This gives ten different symbols for the sense of
touch, each of which corresponds to one of our ten

THE LETTER ON THE BLIND 93

arithmetical characters. Now imagine a board as
large as you choose, divided into small squares
arranged horizontally and separated by a small
space one from the other, as you see in fig. 4, and
you have Saunderson's instrument

You can easily see that there is no number
which cannot be expressed in the tablet, and
hence no arithmetical process which cannot be
carried out therein.

Suppose, for example, that we want to find the
sum of, or to add, the nine following numbers :

I

o

3

4

5

2

3

4

5

6

3

4

5

6

7

4

5

6

7

8

5

6

7

8

9

6

7

8

9

7

8

9

i

8

9

o

i

o

9

o

i

2

3

I write them on the table in the order they are
named : the first figure on the left of the first
number, on the first square to the left of the first
line; the second figure on the left of the first
number, on the second square on the left of the
same line, apd so on.

I place the second number in the second row of
squares ; units are units, tens are tens, etc.

I place the third number in the third row of squares,

94 DIDEROTS PHILOSOPHICAL WORKS

and so on, as you see in fig. 4. Next, touching
with my fingers each vertical row from the top to
the bottom, beginning with that \\hich is most to

FIG. 4.

my left, I add together the numbers therein ex-
pressed ; and I write the tens that are , over at the
end of that column. I pass to the second column,
moving leftward, and work in this way ; thence to
the third, and so on completing my addition*

THE LETTER OX THE BLIND

95

This Is how the same tablet served him to prove
the properties of rectilinear figures. Supposing he
had to prove that parallelograms which have the

FIG. 5.

same base and same height are equal in area, he
placed his pins as you see in fig. 5 ; he added names
to the angles, and proceeded with the proof with
his fingers.

Supposing that Saunderson only used large-

g6 DIDEROTS PHILOSOPHICAL WORKS

headed pins to mark the limits of his fingers, he
could arrange round these small-headed pins of
nine different varieties with all of which he was
familiar. Thus he was never at a loss, except in
cases where the great number of angular points
which he was obliged to name in his proof forced
him to have recourse to the letters of the alphabet.
\Ve are not told how he used them.

We only know that his fingers moved over his
tablet with astonishing rapidity ; that he made the
longest calculations successfully ; that he could
interrupt them, and recognise when he was in
error ; that he could verify them with ease ; and
that this work did not take him as much time as
one might imagine, because he could arrange his
tablet to suit his convenience.

This arrangement consisted in placing large-
headed pins in the centre of all the squares. This
done, he had only to fix their value by small-headed
pins, except in the case when he wished to express
an unit. In that case he put a small-headed pin
in the centre of the square, in place of the large-
headed pin.

Sometimes, instead of forming a complete line
with pins, he only placed them at all the angles or
points of intersection, and round these lie stretched
silk threads which completed his figures (See
fig. 6.)

He left sever al other instruments which facilitated
his geometrical studies ; the use he made of these
is not known, and more acumen would perhaps be

NICHOLAS

Lucafian

To face p. 96.

THE LETTER ON THE BL1XD 97

required to discover this than to solve some problem
in integral calculus. Let some geometrician tr}~ to
discover the function of four pieces of solid wood

mu mm mm

mm mm mm

mm am ms wm mm

FIG. 6.

iii the form of rectangular parallelopipeds, each 1 1
inches by $^ wide and a little more than half an
inch thick, and whose two larger opposite surfaces
were divided into small squares similar to the
abacus 1 have just described ; but with this differ-

7

98 DWEKOTS PHILOSOPHICAL WORKS

ence, that they were only perforated at certain
points, in which pins were driven in up to their
head. Each surface had nine small arithmetical

FIG. 7.

tablets, each with ten numbers, and each ot these
ten numbers was composed of ten figures. Fig. 7
represents one of the small tablets, and here are
the numbers it contained :

THE LETTER OX THE BLIND 99

9

4

o

S

4

2

4

i

8

6

4

i

7

9

2

5

4

2

S

4

6

3

9

6

S

7

i

8

8

7

8

s

6

S

8

4

1

o

5

8

8

9

4

6

4

9

4

o

^

o

He was the author of an excellent work of Its
kind The Elements of Algebra 1 where the only
signs of his blindness are the peculiarity of certain
demonstrations which a sighted man would probably
not have thought of. To him we owe the division
of the cube into six equal pyramids whose apex is
at the centre of the cube and the base of each is
one of its faces. This is used by him as a simple
proof that every pyramid is the third of a prism
having the same height and the same base. His
taste for mathematics, his small means, and the
advice of his friends decided him to give public
lectures. His marvellous facility for clear demon-
stration encouraged his friends to think he would
prove a successful teacher, for he taught his pupils
as if they could not see, and a blind man who makes

1 Printed in London, a year after Saunderson's death, at the expense
of Cambridge University. In 1756 de Joncourt translated it, with some
additional remarks (Amsterdam, 2 vols.)- (Br)

TOO DIDEROTS PHILOSOPHICAL WORKS

himself clear to the blind must be doubly lucid to
the sighted ; it is a telescope the more.

His biographers say that his talk abounded in
happy expressions, and I can well believe it. But
"What do you mean by happy expressions?" you
will perhaps inquire. I answer, madam, it is using
expressions to one sense ^touch, for example)
which are also metaphorical to another sense (say,
sight) : as a result, a double light is shed on the
subject for the hearer, the direct light of the natural
use of the expression and the reflected light of the
metaphor. It is evident that in these cases,
Saunderson, with all his intelligence, was not
aware of the full force of the terms he employed,
since he only realised half of the ideas attached to
these terms. But does not this happen to all of
us at times? It may happen to idiots, who some-
times make excellent jokes, and clever folk who say
a foolish thing, without either being aware of it. I
have observed the want of words produces the like
effect in foreigners, who in an unfamiliar language
are obliged to say everything in very few words,
some of which they unknowingly use very happily.
But every language being to writers of a lively
imagination deficient in fit words, they are in the
same case as clever foreigners : the situations
invented by them, the delicate gradations they
perceive in characters, the natural scenes they draw,
are continually leading them away from ordinary
locutions and causing them to adopt turns of phrases
which never fail to charm when they are neither

THE LETTER ON THE BLIND 101

precious nor obscure. These are faults which are
more or less readily forgiven, according to the
reader's wit and knowledge of the language. This

is why M. de M * is the French author who

most pleases the English, and Tacitus, of all the
classics, bears the bell among the thinkers ; they
do not attend to the licences of the style, it is only
the truth of the expression which strikes them.

Saunderson was extremely successful as professor
of mathematics at the University of Cambridge.
He gave lessons in optics, he lectured on the nature
of light and colours, he explained the theory of
vision ; he wrote on the properties of lenses, the
phenomena of the rainbow, and many other subjects
connected with sight and its organ.

These facts lose much of their marvellous character
when you consider that there are three distinct
elements in a question in which both physics and
geometry enter the phenomenon to be explained,
the hypotheses of the geometrician, and the resultant
calculation. Now it is manifest that, however great
the penetration of the blind man, the phenomena of
light and colour are unknown to him. The hypotheses
he will understand, as all of them relate to palpable
causes ; but the geometrician's reason for preferring
them to others will be out of his ken, as in order to
see that he must be able to compare the hypotheses

1 Naigeon, and after him the editor of 1818. have inserted, instead of
the initials -I/, de J/ . . . in the original edition, M. de Montesquieu.
This is a great mistake ; Diderot himself has given M. de Marivaux in
the index of the 1749 and 1751 editions. The Esprit des Lois appeared
in 1748, which might have caused this error on the part of the editors,
who had not consulted the index. (Br)

io- DIDEROTS PHILOSOPHICAL WORKS

themselves with the phenomena. Therefore the
blind man takes -the hypotheses for what they are
given him, a ray of light for a fine and elastic
thread, or for a succession of minute bodies striking
our eyes \vith incredible velocity, and he makes his
calculations accordingly. The transition is made
from physics to geometry, and the question becomes
purely mathematical.

But what are we to think of the results of the
calculation ? Firstly, that it is sometimes extremely
difficult to obtain them, and that it would be to little
purpose that a man of science could form the most
plausible hypotheses, were he not able to verify
them by geometry ; accordingly the greatest
physicists, Galileo, Descartes, and Newton, were
great geometricians. Secondly, the results are
more or less certain, as the preliminary hypotheses
are more or less complex. When the calculation is
based on a simple hypothesis, the conclusions have
the validity of geometrical proofs. When there are
a great many suppositions, the probability of each
hypothesis being true diminishes in the ratio of the
number of these hypotheses ; but on the other hand
increases owing to the improbability that so many
false hypotheses could be mutually corrective and
produce a result confirmed by the phenomena. A
parallel to this would be an addition, of which the
sum was correct although the sum of groups of
numbers had been wrongly added up. We must
admit that such a result is possible, but at the same
time you see that it would very seldom prove so.

THE LETTER OX THE BLIXD 103

The greater the number of numbers to be added, the
greater the probability of error in the addition of
each, but at the same time this probability is
lessened if the result of the operation be right.
There are therefore a number of hypotheses, the
certainty resulting from which would be the least
possible. If I make A plus B plus C equal to 50,
must I conclude from 50 being the real quantity of
the phenomena that the suppositions represented by
the letters A, B, C are true? Not at all, for there
are numberless ways of subtracting from one of
these letters and adding to the others which would
always give 50 as the result. But the case of three
combined hypotheses is perhaps one of the most
dis favourable.

One advantage of calculation which I must not
omit is, that the contrariety found between the re-
sult and the phenomenon excludes false hypotheses.
If, a man of science proposes to find the curve
formed by a ray of light in passing through the
atmosphere, he must regulate himself by the
density of the strata of air, the law of refraction,
the nature and form of the luminous corpuscles, and
perhaps other essential factors which he does not
include in his calculation, either because he does
not know them or because he deliberately leaves
them out of consideration. He then determines the
curvature of the ray. If the actual curve differs
from that of his calculation, his hypotheses are
incomplete or false. If the actual curvature agrees
with that of his calculation, there are two alterna-

104 DIDEROT S PHILOSOPHICAL WORKS

tives : first that his hypotheses were mutually cor-
rective, secondly that they were correct. But which
is true? He does not know, and yet that is the
certitude to which he can attain.

I read Saunderson's Elements of Algebra carefully
in hopes of meeting what I was desirous of knowing
from those who knew him intimately, and who have
related some particulars of his life ; but my curiosity
was baffled, and it occurred to me that elements of
geometry from him would have been a work both
more singular in itself and of greater use to us. We
should have found in it definitions of point, line,
surface, solid, angle, intersections of lines, and
planes, in which I make no question but he would
have proceeded on principles of very abstract meta-
physics, closely allied to that of the idealists.
Those philosophers, madam, are termed idealists
who, conscious only of their own existence and of a
succession of external sensations, do not admit any-
thing else ; an extravagant system which should to
my thinking have been the offspring of blindness
itself ; and yet, to the disgrace of the human mind
and philosophy, it is the most difficult to combat,
though the most absurd. It is set forth with equal
candour and lucidity by Doctor Berkeley, Bishop of
Cloyne, in three dialogues. 1 It were to be wished
that the author of the Essay on the Origin of Human
Knowledge 2 would take this work into examination ;

1 frialogue s between Hylas and Philonoiis (1713), translated by the
Abbe Gua de Malvin (1750). (A)

a Condillac (1715-1780), whose Essay on the Origin of Human
Knowledge had appeared anonymously in 1746. (A)

THE LETTER OX THE BLIXD 105

he would there find matter for useful, agreeable,
and ingenious observation for which, in a word, no
person has a better talent. Idealism deserves an
attack from his hand, and this hypothesis is a double
incentive to him from its singularity, and much
more from the difficulty of refuting it in accordance
with his principles, which are the same as those of
Berkeley. According to both, and according to
reason, the terms essence, matter, substance, agent,
etc., of themselves convey very little light to the
mind. Moreover, as the author of the Essay on th?
Origin of Human Knowledge judiciously observes,
whether we go up to the heavens, or down to the
deeps, we never get beyond ourselves, and it is
only our own thoughts that we perceive. And this
is the conclusion of Berkeley's first dialogue, and the
foundation of his entire system. Would you not
be curious to see a trial of strength between two
enemies whose weapons are so much alike? If
either got the better it would be he who wielded
these weapons with the greater address ; the author
of the Essay on the Origin of Human Knowledge has
lately given in his Treatise on Systems additional
proof of his adroitness and skill and shown himself a
redoubtable foe to the systematics.

We have wandered far from the blind, you will
say. True, madam, but you must be so good as to
allow me all these digressions ; I promised you a
conversation, and I cannot keep my word without
this indulgence.

I have read as carefully as it was in my power

io6 DIDEROTS PHILOSOPHICAL WORKS

what Saunderson has said on the infinite ; and I
assure you he had such very just and very clear
notions on the subject that in his account most of
our infinitarians would have been looked on but as
blind. You yourself shall be judge : though this
matter be somewhat difficult, and a little beyond
your mathematical knowledge, I trust to bring it
within your grasp and initiate you into the logic of
the infinite.

The case of this famous blind man proves that the
sense of touch, when trained, can become more
delicate than sight, for he distinguished genuine
from counterfeit coins l by passing his hands over
a number of these, although the counterfeits were
sufficiently good imitations to deceive a clear-
sighted connoisseur ; and he judged of the accuracy
of a mathematical instrument by passing the tips
of his fingers along its divisions. This is certainly
more difficult than to judge by touch of the resem-
blance of a bust to the person represented, and this
shows that a blind people might have sculptors and
put statues to the same use as among us to per-
petuate the memory of great deeds, and of persons
dear to them ; and in my opinion feeling such
statues would give them a keener pleasure than we
have in seeing them. What a delight to a passion-
ate lover to draw his hand over beauties which he
would know again, when illusion, which would act
more potently on the blind than on those who see,

1 Memoirs of the life and character of Dr Nicholas Saunderson m
Saunderson's Mfetra, vol. i, p. xi (1740),

THE LETTER ON THE BLIND 107

should come to reanimate them ! But perhaps, as
he would take a deeper pleasure in the memory, his
grief would be the keener for the loss of the original.

Saunderson, like the blind man of Puisaux, was
affected by the smallest atmospheric change, and
could recognise, especially in still weather, the
presence of objects not far from him. It is related
of him that being present during some astronomical
observations taken in a garden, the clouds which
hid the face of the sun every now and then from
the spectators at the same time caused such a change
in the action of the rays on his face as signified
to him the moments which favoured or impeded
the experiments. You may, perhaps, think that
some change in the eye might indicate to him the
presence of light, but not of distant objects, and I
would have supposed so myself, but for the fact
that Saunderson had lost not only his sight but
its organ.

Saunderson, then, saw by means of his skin, *and
this integument of his was so keenly sensitive that
with a little practice he could certainly have re-
cognised the features of a friend traced upon his
hand, and would have exclaimed, as the result of
successive sensations caused by the pencil: "That
is so-and-so." Thus the blind have likewise a paint-
ing, in which their own skin serves as the canvas.
These are no wild fancies, and I am sure if the little

mouth of M were traced on your hand, you would

immediately recognise it. Yet you must allow the
blind man would find this an easier task than you,

io8 DIDEROrS PHILOSOPHICAL WORKS

accustomed though you are to see and admire that
mouth. For two or three elements enter into your
recognition : the comparison of the tracery on your
hand with the picture formed on the ground of your
eye ; the recollection of the manner in which we are
affected by things felt, and of the manner with which
we are affected by things we have only seen and
admired ; finally, the application of these data to the
question of the draughtsman, who asks you when
he draws with his pencil a mouth on the skin of your
hand : " Whose mouth is this which I am drawing ? "
Whereas the sum of the sensations aroused by a
mouth laid on the blind man's hand is the same as
the sum of the successive sensations caused by the
draughtsman's pencil.

I might add to this account of Saunderson and
the blind man of Puisaux, Didymus of Alexandria,
Eusebius the Asiatic, and Nicaise of Mechlin, 1 and
some other people who, though lacking one sense,
seemed so far above the level of the rest of mankind
that the poets might without exaggeration have
feigned the jealous gods to have deprived them of it,
from fear lest mortals should equal them. For what
was Tiresias, who had penetrated the secrets of the
gods, but a blind philosopher whose memory has
been handed down to us by fable? But let us
return to Saunderson and follow the history of this
extraordinary man to his grave.

When he was at the point of death, 2 a clergyman
of great ability, Mr Gervase Holmes, was summoned

1 See note 2, pp. 219, 220. - See Introduction, pp. 10-15, l8 > *9

THE LETTER ON THE BLIXD 109

to his side, and they held a discussion upon the
existence of God, some fragments of which are
extant, and which I will translate to the best of my
ability, for they are well worth it. The clergyman
began by haranguing on the wonders of nature.
"Ah, sir," replied the blind philosopher, " don't
talk to me of this magnificent spectacle, which it has
never been my lot to enjoy. 1 have been condemned
to spend my life in darkness, and you cite wonders
quite out of my understanding, and which are only
evidence for you and for those who see as you do.
If you want to make me believe in God you must
make me touch Him." "Sir/' returned the clergy-
man, very appositely, "touch yourself, and you
wilj recognise the Deity in the admirable mechanism
of your organs."

"Mr Holmes," replied Saunderson, "I must
repeat it, all that does not appear so admirable to
me as to you. But even if the animal mechanism
were as perfect as you maintain, and I dare say it is
(for you are a worthy man and would scorn to
impose on me), what relation is there between such
mechanism and a supremely intelligent Being ? If
it fills you with astonishment, that is perhaps
because you are accustomed to treat as miraculous
everything which strikes you as beyond your own
powers. I have been myself so often an object of
admiration to you, that I have not a very high
idea of your idea of the miraculous. I have had
visits from people from all parts of England who
could not conceive how I could work at geometry :

i io fl/DEROrS PHILOSOPHICAL WORKS

you must allow such folk not to have been very
exact in their notions of the possibility of things.
\Ye think a certain phenomenon beyond human
power and we cry out at once : c 'Tis the handiwork
of a god J ; our vanity will stick at nothing less.
Why can we not season our talk with a little less
pride and a little more philosophy ? If nature offers
us a knotty problem, let us leave it for what it is,
without calling in to cut it the hand of a being who
immediately becomes a fresh knot and harder to
untie than the first. Ask an Indian how the earth
hangs suspended in mid-air, and he will tell you
that it is carried on the back of an elephant ; and
what carries the elephant? A tortoise. And the
tortoise? You pity the Indian, and one might
say to yourself as to him : * My good friend Mr
Holmes, confess your ignorance, and drop the
elephant and the tortoise,'" 1

Saunderson paused, apparently waiting for a
reply, but what possible reply was there to the
blind man ? Mr Holmes availed himself of his good
opinion of his probity and of the abilities of Newton,
Leibniz, Clarke, and some of his fellow-countrymen,
men of the highest genius, who had all been im-
pressed by the wonders of nature and recognised an
intelligent being as its creator. This was certainly
the clergyman's strongest argument. The blind man
admitted that it would be presumptuous to deny
what such a man as Newton had acquiesced in ; yet
he represented to the clergyman that Newton's
1 See note 3, pp. 221, 222. .

THE LETTER ON THE BLIXD in

evidence was not of that weight to him, as that
of all nature to Newton ; while Xewton believed
on God's word, he was reduced to believe on
Newton's word.

" Consider, Mr Holmes," he added, "what a
confidence I must have in your word and in
Newton's. Though I see nothing, I admit there is
in everything an admirable design and order. I hope
you will not demand more. I take your word for
the present state of the universe, and in return keep
the liberty of thinking as I please on its ancient and
primitive state, with relation tu which you are as
blind as myself. Here you will have no witnesses
to confront me with, and your eyes are quite use-
less. Think, if you choose, that the design which
strikes you so powerfully has always subsisted, but
allow me my own contrary opinion, and allow me
to believe that if we went back to the origin oi
things and scenes and perceived matter in motion
and the evolution from chaos, we should meet with
a number of shapeless creatures, instead of a few
creatures highly organised. I make no criticism on
the present state of things, but I can ask you some
questions as to the past. For instance, I may ask
you and Leibniz and Clarke and Newton, who told
you that in the first instances of the formation of
animals some were not headless and others footless ?
I might affirm that such an one had no stomach,
another no intestines, that some which seemed to
deserve a long duration from their possession of a
stomach, palate, and teeth came to an end owing

ii2 DIDEROPS PHILOSOPHICAL WORKS

to some defect in the heart or lungs ; that monsters
mutually destroyed one another ; that all the
defective combinations of matter disappeared, and
that those only survived whose mechanism was not
defective in any important particular and who were
able to support and perpetuate themselves. 1

4< Suppose the first man had his larynx closed, or
had lacked suitable food, or had been defective in
the organs of generation, or had failed to find a
mate, or had propagated in another species, what
then, Mr Holmes, would have been the fate 01 the
human race ? It would have been still merged in
the general depuration of the universe, and that
proud being who calls himself man, dissolved and
dispersed among the molecules of matter, would
have remained perhaps for ever hidden among the
number of mere possibilities. If shapeless creatures
had never existed, you would not fail to assert that
none will ever appear, and that I am throwing
myself headlong into chimerical fancies, but the
order is not even now so perfect as to exclude the
occasional appearance of monstrosities." Then,
turning towards the clergyman, he added, " Look
at me, Mr Holmes. I have no eyes. What have
we done, you and I, to God, that one of us has
this organ while the other has not?"

Saunderson uttered these words in such a sincere
and heartfelt tone that the clergyman and the rest
of the company could not remain insensible to his

1 This is the thesis of Lucretius, and the theory of the survival of the
hltest.(A)

THE LETTER ON THE BLIND 113

suffering, and began to weep bitterly. He noticed
it and said to the clergyman, "Mr Holmes, I was
aware of the kindness of your heart, and I am very
grateful for the expression of it you have given
me just now ; but if you love me, do not grudge
me my dying consolation of never having caused
anyone affliction."

Then, continuing the conversation in a firmer
tone, he added: "I conjecture, then, that in the
beginning, when matter in a state of ferment
brought this world into being, creatures like myself
were of very common occurrence. But might not
worlds too be in the same case ? How many faulty
and incomplete worlds have been dispersed and
perhaps form again, and are dispersed at every
instant in remote regions of space which I cannot
touch nor you behold, but where motion continues
and will continue to combine masses of matter,
until they have found some arrangement in which
they may finally persevere ? O philosophers, travel
with me to the confines of this universe, beyond the
point where I feel and you behold organised beings ;
cast your eyes over this new ocean, and search in its
aimless and lawless agitations for vestiges of that
Intelligent Being whose wisdom fills you with such
wonder and admiration here !

"But what is the use of taking you out of your
element? What is this world, Mr Holmes, but a
complex, subject to cycles of change, all of which
show a continual tendency to destruction ; a rapid
succession of beings that appear one by one, flourish

8

H4 DJDEROTS PHILOSOPHICAL WORKS

and disappear ; a merely transitory symmetry and
momentary appearance of order? A moment ago
I reproached you for estimating the perfection of
things by your own capacity ; I might accuse you
here of measuring duration by your own existence.
You judge of the phases of the world's existence as
the ephemeral insect of yours. The world seems to
you eternal, just as you seem eternal to the creatures
of a day ; and the insect is more reasonable than
you. What a prodigious series of ephemeral genera-
tions witness to your eternity, what an immense
tradition ! Yet we shall all pass away without a
possibility of denoting the real extent which we
took up, or the precise time of our duration. Time,
matter, and space are perhaps but a point, "

During this conversation Saunderson became
more excited than his state of health would permit,
and an attack of delirium ensued, which lasted
several hours. At its close he cried, " O thou God
of Clarke and Newton, have mercy on me!" and
expired.

Such was the end of Saunderson. You see,
madam, that all the arguments of the clergyman he
took exception to were not of a character to con-
vince a blind man. What a disgrace to men who
have no better argument than he ; men who have
eyes, to whom the marvellous spectacle of nature
from sunrise to the setting of the smallest stars
reveals the existence and glory of its Maker ! They
have sight, which Saunderson was deprived of, but
Saunderson was blessed with a purity of life and

'THE LETTER ON THE BLIND 115

uprightness which \ve look for In vain in them.
Accordingly they lead the life of the blind, and
Saunderson died as if he knew the light. The voice
of nature made itself clear to him by the media of
the senses he possessed, and his evidence is the
more convincing against those who obstinately shut
their eyes and ears. Was not the true God more
completely veiled by the mists of paganism for a
Socrates, than for the blind Saunderson, who never
enjoyed the spectacle of nature ?

I am very sorry, madam, both for your sake and
mine, that no further interesting particulars of this
famous blind man have been handed down. His
conversation would perhaps have afforded more light
than all our experiments. Tho^e about him must
have been devoid of the philosophic spirit. I make an
exception in favour of his pupil, Mr William Inchlif,
who only saw Saunderson during his last moments,
and who took down his last words, which I should
advise all who know English to read in the original,
printed in Dublin in 1747, and entitled The Life and
Character of Dr Nicholas Saunderson^ late Lucasian
Professor of the Mathematicks in the University of
Cambridge ; by his disciple and friend William
Inchlif, hsq.^ They w T ill find a charm, and a
vigour in this, scarce ever paralleled, but which I
do not flatter myself I have conveyed in translation,
in spite of all my care.

1 By rendering a Dr Inchlif responsible for his imaginary reconstruc-
tion of Saunderson 's last moments Diderot alienated the sympathies of
England. (A)

1 16 D1DEROTS PHILOSOPHICAL WORKS

He married in 1713 the daughter of Mr Dickons,
rector of Boxworth, in the county of Cambridge, and
had by her a son and daughter who are still living.
His farewell to his family was exceedingly moving.
" I go," said he, "to our common destination;
spare me laments which unman and unnerve. The
expressions of grief which escape you only make
me conscious of my own. I gladly give up a life
which has been for me a long desire, a constant
privation. Live on, as virtuous as I, but more
fortunate, and learn to die with equal calm." He
then took his wife's hand, which he held for a moment
clasped in his own ; he turned his face towards her as
if he desired to see her ; he blessed his children,
embraced them, and begged them to leave him,
because they caused him greater grief than the
approach of death.

England is the land of philosophy and of scientific
inquiry, yet without Mr Inchlif we should only
know what the common man could have narrated of
Saunderson ; for instance, that he recognised places
he had once visited by the sound the walls and
pavement reflected, and many similar anecdotes,
all equally common to the majority of the blind.
Strange ! Are blind men of such high intellectual
abilities as Saunderson of common occurrence in
England, and are men born blind who lecture on
optics to be met with every day?

People try to give those born blind the gift of
sight, but, rightly considered, science would be
equally advanced by questioning a sensible blind

THE LETTER ON THE BLIND 117

man. We should learn to understand his psychology
and should compare it with ours, and perhaps we
should thereby come to a solution of the difficulties
which make the theory of vision and of the senses
so intricate and so confused. But I own I cannot
conceive what information we could expect from a
man who had just undergone a painful operation
upon a very delicate organ which is deranged by the
smallest accident and which when sound is a very
untrustworthy guide to those who have for a long
time enjoyed its use. For my part, as to the theory
of the senses, 1 would sooner hear a metaphysician
who was acquainted with the principles of meta-
physics, the elements of mathematics, and the con-
formation of the organs of sense, than an uneducated
man whose sight was first due to an operation for
cataract. I would have less confidence in the im-
pressions of a person seeing for the first time than
in the discoveries of a philosopher who had profoundly
meditated on the subject in the dark ; or, to adopt
the language of the poets, who had put out his eyes
in order to be the better acquainted with vision.

To obtain some certainty in such experiments the
subject must at least have been prepared a long time
beforehand ; he should be made a philosopher no
rapid process even with a philosopher for teacher !
And imagine the task if the teacher were not
enlightened, or (worse still) fondly and mistakenly
imagined himself enlightened ! It would be better
to postpone the investigation to a considerable period
after the operation. To do this, the patient would

i IS DIDEROTS PHILOSOPHICAL WORKS

have to remain in darkness, and the investigator
would have to see to it that his wound was healed
and his eyes perfectly sound. I would not expose
him to full daylight for the first time. A strong
light dazzles our eyes ; what effect will it not have
on an organ which cannot but be extremely tender
and sensitive, and which has never yet felt any
impression to blunt it?

But this is only the beginning. It would be a
difficult and delicate task to reap any benefit even
from a person thus prepared, and to adapt our
questions so that he may precisely say only what
passes in himself. This interrogatory should be
held in presence of the Academy ; or rather, to avoid
the presence of idle spectators, only such as deserve
that distinction by their knowledge of philosophy,
anatomy, etc., should be invited.

The task would not be beneath the intelligence of
the best and wisest of men ; to train and question
one born blind would be an occupation worthy of
the combined talents of Newton, Descartes, Locke
and Leibniz.

I will end my letter, which I own is already too
lengthy, by a problem which was propounded some
time ago. Some reflections upon Saunderson's
singular condition tend to show that it has never
been absolutely solved. Suppose one blind from
birth has been taught to distinguish by touch a cube
and a sphere of the same metal and of approximately
the same size, so that when he touches them he can
say which is the cube and which is the sphere.

THE LETTER ON THE BLIND 1 19

Suppose the cube and sphere placed on a table
and the blind man suddenly to see ; can he dis-
tinguish the cube from the sphere by sight without
touch ?

Mr Molyneux first stated this problem and
attempted to solve it. He declared that the blind
man would not distinguish between the cube and
the sphere; "for, "said he, "though he has learnt
by experience the effect of a sphere and a cube upon
the sense of touch, he does not yet know that what
affects his sense of touch in such and such a manner
must affect his sight thus or thus ; nor that the pro-
jecting angle of the cube which presses against his
hand should appear to his eyes as it actually does
appear in the cube."

Locke, 1 when consulted on this point, said: "I
certainly agree with Mr Molyneux's opinion. I
believe the blind man incapable at first sight of
affirming with any certainty which was the cube
and which the sphere if he merely looked at them,
although, if he touched them, he could name them
and distinguish between them by the difference of
their shape, which he would recognise by touch. "

The Abb de Condillac, 2 whose Essay on the Origin
of Human Knowledge you have read with so much
pleasure and profit, and whose excellent Treatise on
Systems accompanies this letter, makes an original
contribution to the question. I shall not repeat his
arguments here, since you will have the pleasure of
reading his book in which they are expounded in

i See note 4, pp. ^2, 223, 8 See note 5, pp. 223-5,

120 DIDEROrS PHILOSOPHICAL WORKS

such an entertaining and yet such a philosophical
manner that it would be a mistake on my part to
tear them from their context. I shall merely observe
that they all tend to prove that the born-blind either
sees nothing, or distinguishes between the sphere
and the cube ; and that the conditions that these
two bodies should be of the same metal and of
approximately the same size (which was postulated
in the problem) are unnecessary, which cannot be
disputed ; for he might have said, if there be no
essential connection between the sensations of the
sight and the touch ('as Messrs Locke and Molyneux
assert), they must admit that a body may to the eye
appear to have two feet in diameter which yet would
vanish on being touched. De Condillac adds, how-
ever, that if the blind man sees bodies and dis-
tinguishes their forms, and yet hesitates what to
think about them, it must be from metaphysical
reasons, and those not a little subtle, which I shall
presently explain. We have here two different
opinions on the same question a difference between
philosophers of the 1 highest rank. One would
suppose, after the problem had been studied by
men such as Messrs Molyneux, Locke and the
Abb de Condillac, that nothing more could be
said ; but the same thing can be viewed from so
many different sides that it is not strange if they
have not exhausted all its possibilities.

Those who declare that a man blind from birth
could not distinguish between a cube and a sphere
have set out by assuming a fact which perhaps should

THE LETTER ON THE BLIND 121

have been investigated ; that is, whether a blind man
who has had his cataracts removed is in a condition
to use his eyes immediately after the operation.
They merely say: "The blind man, comparing the
ideas of spheres and cubes which he has received by
the sense of touch with those received by sight, will
necessarily know them to be the same ; and it would
be indeed odd if he were to name that body a cube
which gives the eye the idea of a sphere, and sphere
that which gives the idea of a cube. He will there-
fore call those bodies spheres and cubes at sight
which he called spheres and cubes by the sense of
touch."

But how do their antagonists reply ? They have
also taken for granted that the blind man could see
immediately his organ was perfect ; they supposed
that an eye couched for cataract was like an arm
that ceases to be paralysed. As the latter does not
need exercise before it feels, they said, neither does
the former before it sees; and they added: "Let
us grant the blind man a little more philosophy
than you afford him, and after carrying on the reason-
ing where you left it, he will continue thus : * But
still, who is to assure me that when I approach
these bodies and touch them with my hands they
will not on a sudden deceive my expectation, and
that a cube will not give me the sensation of a sphere
and a sphere of a cube ? Experience alone can teach
me whether there be an analogy between sight and
touch. The reports of these two senses may well
be contradictory without my knowing it ; nay, I

122 DTDEROTS PHILOSOPHICAL WORKS

should perhaps suppose what is actually present to
the sight to be only a mere appearance, had I not
been informed that they are the very same bodies
I had touched. This object certainly seems to be
the body which I called a cube ; and that, the body
I called a sphere ; but the question is, not what 1
think, but what is ; and I am not in a position to
answer the latter question satisfactorily.' "

The line of argument, says the author of the
Essay on the Origin of Human Knowledge, would be
extremely perplexing to him who had been born
blind, and I see nothing but experience which can
furnish an answer to it. It seems probable that
the Abbe de Condillac means only the experiment
repeated by the blind man himself on a second
handling of these bodies. You will soon perceive
why I make this point That able metaphysician
might have added that the blind man would be
the more inclined to suppose that two senses might
be mutually contradictory, as he conceives that a
mirror makes them mutually contradictory, as I
have noticed already.

De Condillac proceeds to observe that Molyneux
has confused the issues of the problem by laying
down several conditions which are irrelevant to the
metaphysical difficulties which the blind man would
experience. This criticism is the more just, as the
supposition of the blind man being acquainted with
metaphysics is not at all out of the way ; because the
experiment in all such philosophical questions should
be accounted to be made on a philosopher that Is

THE LETTER ON THE BLIND 123

to say, on a person who perceives In the questions
propounded all that his reason and the state of his
organs permit him to perceive. Such, briefly,
are, madam, the pros and cons of the problem ;
and you shall now see by my examination of It
how very far they, who asserted that the blind
man would see geometrical figures and distinguish
between them, were from realising that they were
right ; and what good reason their opponents had
to think that they were not in the wrong.

This problem of the blind man, stated in some-
what more general terms than by Molyneux,
embraces two problems which we will consider
separately. \Ve may ask (i ) if the blind man would
see immediately after the operation for cataract ;
(2) supposing he is able to see, could he see well
enough to distinguish between figures ; could he,
in seeing them, correctly give them the same names
which he gave them by the sense of touch ; and if
he can, prove that these names are the right ones ?

Will the man born blind see immediately after
the cure of the organ ? Those who maintain that
he will not see, say: " Directly the blind man is
able to use his eyes, all the scene before him is
represented at the back of the eye. This image,
which is composed of a number of objects concen-
trated in a very small space, is but a confused mass
of figures which he will not be able to distinguish.
People are on the whole agreed that it is only ex-
perience which can enable him to judge of the dis-
tance of objects, and that he is obliged to approach,

i2 4 DIDEROTS PHILOSOPHICAL WORKS

touch, draw back from, and again approach and
touch them to assure himself that they are not part
of himself and are foreign to his essence ; that he
is now near and now far from them. Why should
not experience be a necessary preliminary for per-
ceiving them ? Without previous experience he who
perceives objects for the first time would suppose,
when he is out of sight of them, that they had
ceased to exist ; for it is only our experience of per-
manent objects and such as we find again in the
same place where we left them which evidences
the continuity of their existence when out of our
sight. It is perhaps for this reason that children
are so readily consoled for toys taken from them.
It cannot be said that they promptly forget them,
for some children only two and a half years old
know a considerable number of words of a language
and are more at a loss to pronounce them than to
retain them. Now, this is a proof of childhood's
being the very season of memory.

Is it not a more likely hypothesis that children
think that what they no longer see no longer exists,
especially as their joy when things they have lost
sight of appear again is mixed with surprise ?
Nurses help them to acquire the notion of the
continuance of absent persons by playing a game
which consists in hiding the face, and showing it
again. Thus they learn a hundred times in a
quarter of an hour that what ceases to appear does
not necessarily cease to exist. Whence it follows
that we owe the notion of the continuous existence

THE LETTER ON THE BLIND 125

of objects to experience, of their distance to the
sense of touch ; that the eye may perhaps have to
learn to see as the tongue to speak ; that it would
not be surprising should the aid of one of the
senses be necessary to another ; and that touch,
which ascertains the existence of objects exterior to
ourselves when present to our eyes, is likewise the
sense to which the confirmation not only of their
figures, and other details of these objects, but even
their presence, is reserved.

To these arguments may be added the famous
experiment of Cheselden. 1 The young man from
whose eyes this skilful surgeon removed cataracts
was for a long time unable to distinguish dimensions,
distances, positions, or even figures. An object an
inch in size held before his eye so as to hide a house
from him appeared as large as the house itself. All
he saw seemed as close to his eye as the object
he touched to the skin. He could not distinguish
what he judged round by touch from what he had
judged angular ; nor distinguish by sight whether
what he had felt to be above or beneath him were
in reality above or beneath him. He eventually
succeeded, but not without difficulty, in perceiving
that his house was larger than his room, but he
could not conceive how this could be ascertained by
sight. Repeated experiments were necessary before
he became assured of paintings representing solid
bodies ;' and when he was quite convinced by looking
at pictures that what he saw was not bare surfaces,

1 See note 6, p. 225.

126 DfDEROrS PHILOSOPHICAL WORKS

on putting his hand to a picture he was vastly
surprised at finding a plane surface without any
relief. Me then asked which was deceptive, the
sense of touch or the sense of sight ? Painting
likewise has the same effect on savages. They take
the painted figures for living men, question them
and are astonished at receiving no answer ; and
this error in them certainly did not proceed from
their not being accustomed to see.

But what can be answered to the other difficulties ?
That the trained and practised eye of a man sees
better than the weak and untrained organ of an
infant, or of one born blind who has had his eyes
couched. Look, madam, at the proofs adduced
by the Abbe de Condillac at the end of his Essay
on the Origin of Human Knowledge^ where he also
adduces Cheselden's experiments as related by
Voltaire. The effects of light upon an eye for the
first time so affected, and the conditions required in
humours of that organ, the cornea, the crystalline
lens, etc., are clearly and ably specified therein,
and leave little doubt that the vision of an infant
opening its eyes for the first time, or a blind person
who has just been operated upon, is very imperfect
We must, therefore, admit we perceive a multitude
of details in objects unperceived by the infant or
one born blind, though these objects are equally
represented at the back of their eyes ; for objects
to strike us is not enough we must further attend
to these experiences ; that, consequently, we see
nothing the first time we use our eyes ; and during

THE LETTER ON THE BLIND 12;

the first moments of sight we only receive a mass of
confused sensations, which are only disentangled
after a time and by a process of reflection. It is
by experience alone that we learn to compare our
sensations with what occasions them ; that sensa-
tions having no essential resemblance with their
objects, it is from experience that we are to inform
ourselves concerning analogies which seem to be
merely positive. In short, that touch is of great
service in giving the eye an accurate knowledge of
the conformity of the object to the sense-impression
received of it is unquestionable ; and I am much
Inclined to think that were not everything in nature
subject to laws infinitely general if, for instance,
the pricking of certain hard bodies were painful,
and that of certain other bodies pleasurable we
should die before we had received the hundred-
millionth fraction of the experiences necessary for
the preservation of our body and our well-being.

I am not, however, of opinion that the eye is
incapable of learning, or, if I may say so, of ex-
perimenting alone. To ascertain the existence and
form of objects by touch, there is no necessity of
seeing ; why should touch be necessary for complete
realisation of the same objects by sight ? I am
awake to all the advantages of touch ; I have not
disguised them in these observations on Saunderson
or the blind man of Puisaux ; but I cannot allow it
that prerogative. It is easy to see that the use of
one sense may be perfected and accelerated by the
observations of another ; but not that there is an

US DIDEROTS PHILOSOPHICAL WORKS

essential interdependence between their functions.
There exist certainly properties in bodies which we
should never perceive without touch ; and by touch
we learn the presence of certain details invisible to
the eye, which only becomes aware of these when
informed by the sense of touch ; but their services
are mutual ; and in the case of persons who have
sight more highly developed than touch it is the
former which warns the latter of the existence 01
objects and of details which would pass unnoticed
from their minuteness. If unknown to you a piece
of paper or some smooth, thin, and flexible substance
were placed between your thumb and index finger,
it is your eye alone which would inform you that
the contact between your two fingers was not direct.
It would be much more difficult, I may cursorily
add, to deceive a blind man than a person used to
see in this.

An eye which is in sound condition and freely
exercised might have some difficulty in convincing
itself that exterior objects are not part of itself;
that some things are distant, some near ; that they
have forms ; that some are larger than others ; that
they have depth, etc. ; still, I make no doubt that
at length it would come to see them, and to see
them so distinctly as to distinguish at least their
more obvious limits.

To deny this would be to set aside the aim and
object of the organs; it would be forgetting the
chief phenomena of vision ; it would be concealing
from oneself that there is no painter of such skill

THE LETTER ON THE BLIND 129

as to rival the beauty and exactness of the miniatures
which are painted in the back of your eyes ; that
there is nothing more exact than the likeness of the
representation to the object itself; that. the canvas
of this picture is not so very small, that there is
no confusion among the various forms, and that they
occupy about a square half-inch ; and that nothing
is more difficult to explain than how the sense of
touch would begin to teach the eye to see were the
use of the latter organ absolutely impossible without
the aid of the former.

But, instead of bare presumptions, I ask you
whether it is touch that teaches the eye to distinguish
colours? I do not suppose such an extraordinary
claim will be made for touch ; and this being so, it
follows that if a blind man who has just been given
the gift of sight is shown a black cube or a red
sphere on a white background, he will immediately
discern the several outlines of these figures.

Delay will be caused, some may object, by the
time which must elapse for the humours of the eye
to assume their proper dispositions, for the cornea
to assume the convexity requisite for vision, for the
pupil to be susceptible of the dilation and contraction
proper to it, for the filaments of the retina to be
sensitive in the right degree to the action of light,
for the crystalline to exercise its forward and back-
ward movement or for the muscles to fulfil their
functions well, for the optic nerves to become
accustomed to the transmission of sensation, for
the entire eyeball to accommodate itself to all the

9

130 DIDEROTS PHILOSOPHICAL WORKS

necessary dispositions, and for all its component
parts to combine in the execution of that miniature,
which so much illustrates the demonstration that
the eye will bring itself to the requisite experience.

I own that, plain as the picture is which I have
now represented to the eye of one born blind, he
will not be able clearly to distinguish its parts until
all these above conditions are combined ; but that
is perhaps the work of a moment ; and it would
not be difficult, by applying the aforesaid argument
to a complicated mechanism such as a watch, to
prove by enumerating all the movements which
take place in the drum, the fusee, the wheels, the
pallets, the pendulum, etc., that the hand would
take a fortnight in moving the space of a second.
If it is objected that these movements are simulta-
neous, I reply that so perhaps are the movements
in the eye when it opens for the first time, and
most of the consecutive judgments. Whatever are
the conditions in the eye requisite for vision, it
must be granted that it is not touch which imparts
them to it, that the organ acquires them independ-
ently ; consequently, will succeed in distinguishing
the figures represented therein without the aid of
another sense.

But when does this occur?, some will say.
Perhaps far sooner than is thought. When we
went together to the Jardin Royal, do you
remember the experiment with the concave mirror
and your fright when you saw the point of a sword
making at you with the same swiftness as the point

THE LETTER ON THE BLIXD 131

of that which you pushed towards the surface of the
mirror ? And yet you were sufficiently accustomed
to refer objects represented in mirrors to something
beyond them. Experience, therefore, is not so
very necessary, nor so infallible as imagined, for
perceiving objects or their images where they are.
Your very parrot gives proof of it. The first time
he saw himself in a mirror, he touched it with his
beak, and as he did not reach himself (whom he
took for a fellow-parrot) he walked round the mirror.
I am not for laying more than due weight on the
instance of the parrot ; still, it is an experiment with
an animal in which preconceived notions cannot be
supposed to have any share.

Yet if I were told that a man born blind saw
nothing for the space of two months, I should not
be surprised. I shall only conclude from it the
necessity of the organs becoming practised, not the
necessity of touch. It will be another reason why
it is important to let such a person remain for some
time in the dark, when he is to be the subject of
experiment ; to allo\v him the opportunity of exer-
cising his eye, which will be done more conveniently
in the dark than in full daylight ; and only to
permit a kind of twilight during the experiments,
or at least to arrange for the increasing or diminish-
ing of light at pleasure in the spot where the
experiments take place. I shall only be the more
inclined to agree that such experiments will always
be very difficult and uncertain ; and that the best
and shortest (though superficially the longest) way

132 DIDEROT'S PHILOSOPHICAL WORKS

would be to arm the subject with a philosophical
training sufficient to enable him to compare the two
conditions he has known, and to acquaint us with
the difference between the state of a blind person
and of one who has his sight. Once more, what
precision is to be expected from one who has not
the habit of thought and analysis, and who, like
Cheselden's blind man, is so ignorant of the benefits
of sight as to be insensible to his misfortune, not
conceiving that the lack of this sense very much
impairs his pleasure? Saunderson, who certainly
deserves the name of philosopher, was not thus
indifferent, and I doubt much whether he would have
agreed with the author of the excellent Treatise on
Systems ; I suspect the latter to have fallen into a
** system" himself when he writes that, "had the
life of man been only an uninterrupted sensation of
pleasure or of pain, happy without prospect of pain,
wretched without any prospect of pleasure, he would
have rejoiced or suffered ; and that if he were so
constituted, he would not have looked about him to
discover if some influence were well disposed towards
him, or desired to injure him ; it is only the alterna-
tion between these two conditions which causes him
to reflect," etc.

Can you believe, madam, that by a clear train
of reasoning (for that is the Author's method of
philosophising) he would ever have been led to
this conclusion? It is not with happiness and
misery as with light and darkness ; the one is not
simply the privation of the other. We might,

THE LETTER OX THE BLIXD 133

perhaps, have entertained the idea that happiness was
as essential to us as existence and thought, had we
enjoyed it without intermission ; but I canrot say
the same with regard to unhappines?. It would have
been very natural to look on it as a forced condition,
to feel oneself innocent, yet to believe oneself guilty
and to accuse or excuse nature as at present.

Does the Abbe de Condillac suppose that a child
in pain only cries from his pain not having been
without intermission from his birth? If he replies
that st existence and pain would be one and indivis-
ible for one who had always suffered, and that such
an one could not imagine cessation of suffering with-
out cessation of his existence," I make reply : ** The
man living in continual misery possibly might not
have said, 4 What have I done that I should suffer
thus?' but why might he not have said, * What
have 1 done that I should be brought into being ? ' "
At the same time, I see no reason why he should
not have used his two synonymous verbs, I exist and
I suffer, the one in prose, the other in poetry, as
we use the two expressions, I live and I breathe.
Moreover, madam, you will observe better than I
do that this passage of the Abbe de Condillac's is
admirably fine, and I fear you may say, after com-
paring my criticism with his reflections, you prefer
an error of Montaigne's to a truth of Charron's.

You may blame my continual digressions. But
digressions are of the essence of this treatise. Now
my opinion on the two foregoing questions is this :
the first time the eyes of one born blind open to the

134 DIDEROTS PHILOSOPHICAL WORKS

light, he will see nothing at all ; some time will be
necessary for his eye to practise sight ; it will
practise alone and without the aid of touch, and
will eventually distinguish not only colours but the
main outlines of objects. Supposing he acquired
this aptitude in a very short space of time, or
acquired it b} T using his eyes in the dark apartment
in which he had been confined and urged to use that
exercise for some time after the operation and
before the experiments ; let us now see whether he
would recognise at sight the bodies he had touched,
so as to give them the proper appellations. This is
the final question.

In order to treat "the question in the manner you
will appreciate for you like method I will classify
the persons on whom the. experiment might be
made. If they are dullards without education and
knowledge and also unprepared, I hold that when
the operation for cataract has completely removed
the defect of the eye and the eye is in a healthy
state, objects would be very distinctly pictured in
it ; but such patients, being unaccustomed to any
kind of reasoning and not knowing anything of
sensation or idea, would be unable to compare the
sensations they had received by touch with those
they now receive by sight, and would at once
exclaim, "There is a round, there is a square," so
that their judgment is not to be relied on ; or even
they will possibly own that they saw nothing in the
objects jpresent to their sight like what they have
handled.

THE LETTER ON THE BLIXD 135

Another class there is, who by comparing the
forms they see with the bodies that had previously
made an impression upon their hands, and mentally
applying touch to distant objects, would describe
one body as a square, and another as a circle with-
out well knowing why, their comparison of the ideas
they have acquired by sight not being sufficiently
distinct in their minds to convince their judgment.

I pass to a third class of subject, a metaphysician.
He, I make no doubt, would, directly he began to
see objects clearly, reason as if he had seen these
bodies all his life ; and after comparing the ideas
acquired by sight with those acquired by touch he
would declare as confidently as you or I : " I am
very much inclined to think that this is the body
which I have always called a circle, and that again
what I named a square, but will not assert it to be
really so. What is to prevent their disappearance
if I were to touch them? How am I to know
whether the bodies I see are also meant to be
touched? I do not know whether visible things are
palpable ; but were I assured of this, and did I take
the word of those about me that what I see is really
what I have touched, I should be no better off!
These bodies may transform themselves in my hands
and transmit on contact sensations quite different
from those resulting from sight. ** Gentlemen,"
would he conclude, "this body appears to be the
square, that the circle ; but that they are the
same to touch as to sight is what I have no know-
ledge of/*

136 DIDEROT S PHILOSOPHICAL WORKS

If \ve take as our subject a geometrician instead
of a metaphysician, he will likewise say of the two
figures he has before his eyes, one is what he used
to call a square, the other what he used to call a
circle : " For I see," he would add, " that it is only
in the former I could arrange my threads and insert
my large-headed pins which denoted the angles of
the square ; and only in the latter figure I could
place the threads I required to demonstrate the
properties of a circle. Here is a circle, then, and
here is a square. But," he would have added with
Locke, * ' perhaps when I lay my hands on these
figures they will change one into another, so that
the same figure would serve me in demonstrating
the properties of a circle to the blind and the pro-
perties of a square to the sighted. I might possibly
see a square and at the same time feel a circle. No, "
he would have continued, " I am wrong. Those to
whom I demonstrated the properties of the circle
and the square had not their hands on my abacus,
and did not touch the threads which I had stretched
to outline my figures, and yet they understood me ;
they therefore did not see a square when I felt a
circle, otherwise we should have been at cross-
purposes ; I should have been outlining one figure
and demonstrating the properties of another, I
should have given them a straight line for the arc of
a circle, and an arc for a straight line : but as they
all understood me, all men see alike : what they saw
as a square, I see as a square ; what they saw as
a circle, 1 see as a circle. So this is what I have

THE LETTER ON THE BLIND 137

always called a square and that is what I have
always called a circle." I have substituted a circle
for a sphere and a square for a cube, because there
Is reason to think that we only judge of distances by
experience ; and of course he who uses his eyes for
the first time sees only surfaces without knowing
anything of projection, since a projection consists in
certain points appearing nearer to us than others.

But even if the blind man were able in his first
attempt to judge of the projection of solidity of
bodies and distinguish not only a circle from a square
but likewise a sphere from a cube, yet I do not
therefore think that this will hold good with regard
to the case of more composite bodies. There is reason
to suppose that Monsieur de Reaumur's blind woman
distinguished between colours, but the odds are thirty
to one that what she said of the sphere and the cube
was purely guesswork. I am firmly persuaded that
it was not possible for her (without inspiration) to
recognise her gloves, her dressing-gown, and her
shoes. These objects are so composite and full of
detail ; there is so little resemblance between their
total shape and that of the limbs they are designed
to adorn or cover that Saunderson would have been
infinitely more perplexed to find out the use of his
mortar-board than d'Alembert or Clairaut to dis-
cover the use of his tables.

Saunderson would infallibly have supposed a
geometrical relation between the object and its use,
hence he would have recognised that his skull-cap
was made for his head, for this had no arbitrary

138 DIDEROTS PHILOSOPHICAL WORKS

form to confuse him. But what would he have
thought of the points and tassel of his mortar-
board ? What was the use of the tassel, or why four
points rather than six? And, these two ornamental
peculiarities would for him have been the source of
a number of absurd theories, or rather an excellent
satire upon what we call good taste.

Taking everything into mature consideration,
it will be admitted that the difference between a
person who has always seen, but to whom the use
of an object is unknown, and one who knows the
use of an object, but has never seen, is not to the
latter's advantage. Yet, do you think, madam, if
you were shown a head-dress to-day for the first
time, you would ever guess it to be an ornament,
and particularly intended for the head ? But if it
be more difficult for one born blind and seeing for
the- first time to form a correct idea of complex
objects, what is there to prevent him taking a
person dressed and sitting motionless in an arm-
chair for a machine or a piece of furniture, and a
tree with its leaves and branches tossed by the
wind for a self-moving, animated, and thinking
being ? How much our senses suggest to us ; and
were it not for our eyes how apt should we be to
suppose that a block of marble thinks and feels !

It is certain, therefore, that Saunderson would
have been assured of his not being mistaken in the
judgment he had just given of the circle and the
square, and that there are cases when the reasoning
and experience of others are of value in elucidating

THE LETTER ON THE BLIND 139

the relation of sight to touch, and in teaching that
what a thing is to the eye, it is likewise to touch.

It would, however, be not the less essential in
demonstrating some proposition of universal applica-
tion (as it is termed) to test the proof by depriving
it of the evidence of the senses ; for you are
very well aware, madam, that if some person
attempted to prove to you that two parallel lines
seen in perspective are to be represented in a picture
by two converging lines, because the two sides of
an avenue appear to converge, it would be forgetting
that the proposition is as true for one that is blind
as for himself. But the foregoing supposition of
one born blind suggests two others : firstly, of a
man who had always seen, but was devoid of the
sense of touch ; secondly, of a man in whom the
senses of sight and touch were mutually contra-
dictory. We might ask the former whether, if the
missing sense were given him, or sight were obscured
by a bandage, he would recognise bodies by touch.
It is clear that geometry (provided he were
acquainted with that science) would be an infallible
guide as to whether the evidence of the two senses
were contradictory or no. All he would have to do
would be to take the cube or sphere in his hand,
and demonstrate its properties, and pronounce that
what he feels a cube is a cube to the eye ; hence it
is a cube he holds. As to one who is ignorant of
this science, I believe he would not more easily
distinguish a cube from a sphere by touch than
Molyneux' blind man distinguished them by sight.

140 DIDEROTS PHILOSOPHICAL WORKS

In the case of a man in whom the sensations of
sight and touch are in a perpetual contradiction, I
do not know what he would think of shapes, order,
symmetry, beauty, ugliness, etc. In all probability
he would be with regard to those things as we are
with regard to the real extension and real duration
of beings. He would, in general, say that a body
possesses a shape, but he must be inclined to think
that it is neither that which he sees nor that which
he feels. Such an one might be dissatisfied with
his senses, but his senses would be neither satisfied
nor dissatisfied with the objects. Were he inclined
to charge one sense with inaccuracy, I imagine it
would be touch. A hundred circumstances would
incline him to think that the form of objects changes
rather by the action of his hands upon them than
by that of the objects on his eyes. But in conse-
quence of these preconceived notions, the difference
between hardness and softness which he would find
in bodies would be very perplexing to him.

But does It iollow that figures are better known
to us because our senses are not self-contradictory ?
Who has told us that they are not false witnesses ?
Yet we pass judgment. Alas ! madam, when we
weigh our human knowledge in Montaigne's scale
we are almost reduced to adopting his motto. For
what do we know ? What of the nature of matter ?
Nothing. What of the nature of spirit and thought ?
Still less. What of the nature of movement, space
and duration ? Absolutely nothing. What of the
truths of geometry ? Ask any honest mathema-

THE LETTER ON THE BLIND 141

ticians, and they will own to you that all their pro-
positions are identical, and that so many volumes
upon the circle (for example) are nothing but
repetitions by a hundred different methods that
it is a figure where all the lines drawn from the
centre to the circumference are equal. Thus we
scarce know anything, yet what numbers of books
there are whose authors have all pretended to know-
ledge I I cannot think why the world is not tired of
reading so much and learning nothing, unless it be
for the very same reason that I have been talking
to you for two hours, without being tired and with-
out telling you anything. 1

With profound respect,

I am, madam,
Your very humble and obedient servant. 1

1 [This translation has been collated with an eighteenth-century
translation, undated and anonymous, entitled a Letter on Blindness,]

ADDITION TO THE PRECEDING
LETTER 1

I AM going to jot down, anyhow, on paper, certain
phenomena of which I was then ignorant, and which
will serve as proofs or refutations of certain para-
graphs in my Letter on the Blind. I wrote the latter
thirty-three or thirty-four years ago, and I have re-
read it without partiality, and am not entirely dis-
satisfied with It. Although the first portion seemed
to me more interesting than the second, and I felt
that the former could have been further extended,
the latter much abbreviated, I left both as I had
written them, for fear that the young man's work
might suffer by the old man's retouching. I think
I should find it impossible to-day to emulate all that
passes muster in ideas and in expression ; and I fear
I am equally unable to correct what merits criticism.
A famous contemporary painter spends the evening
of his life in spoiling the master-pieces produced in
his maturity. I know not if the defects he finds in
them are real ; but either he never possessed the

1 ** We have appended to the Letter on the Blind 'the sequel which
Diderot composed a long time after it. ... Those who accuse the
writer of having always written hastily or of having always been hard
and positive have certainly not read all his works. This sequel alon&
would confute them." (Defting, B)

142

ADDITION TO THE PRECEDING 143

talent to improve them if he carried the imitation
of nature to the extreme limits of art ; or, If he
possessed it, he has lost it, for all human qualities
perish as a man decays. There comes a time when
taste gives counsels which are recognised as just,
but which we are unable to follow.

It is the weakness of spirit arising from the
knowledge of weakness, or laziness which is one
of the results of weakness and want of spirit, which
stands in the way of a labour which would detract
from the value of my work rather than improve it :

Solve senescentem mature sanus equum^ fie
peccet ad extremum ridendus^ et ilia ducat* 1

Horace, Epistolar^ lib. i, epist. i, v. S, 9.

Phenomena

I. An artist who Is both an enlightened student
of the theory of his art, and unequalled in its practice,
has assured me that it was by touch and not by
sight that he judged of the soundness of kernels ;
and that he rolled them gently between his thumb
and first finger, and so discovered by successive im-
pressions small inequalities of surface which were
invisible to his eye.

II. I have heard of a blind man who recognised
by touch the colour of stuffs.

III. I could name one who arranges the colours
of bouquets with the taste upon which Jean Jacques

1 " You would be wise to turn loose the eld horse in good time, lest he
fail in the end, amid laughter^ and strain himselfC" 1

144 DIDEROTS PHILOSOPHICAL WORKS

Rousseau prided himself when, whether in jest or
earnest, he confided to his friends his scheme for
setting up a school to teach the flower-sellers of
Paris.

IV. At Amiens there was a blind dresser who
presided over numerous workmen as well as if he
had the gift of sight.

V. In the case of one sighted man the use of his
eyes destroyed his certainty of touch ; and in order
to cut his hair, he removed the mirror and placed
himself before a bare wall. The blind man who
does not see a danger that threatens him is the
more courageous, and I am sure he would walk
with firmer step over the narrow and elastic planks
bridging a precipice. There are very few who are
undismayed by the sight of abysses beneath them.

VI. Everyone has heard of the famous surgeon
Daviel. 1 I was often present during his operations.
He removed a cataract from the eyes of a blacksmith
who had contracted this disease from exposure to
the fire of his forge ; and during twenty-five years
of blindness he had grown so accustomed to the
guidance of touch that he had to be forced to use
the sense which had been restored to him. Daviel
would beat him and say, ' ' Use your eyes, you
wretch!" He walked and moved, and did all that
we do with our eyes open, with his eyes shut.

1 Jacques Daviel, surgeon, born in 1696. In 1728 he made a special
study of diseases of the eye, and acquired such a high reputation for skill,
that in the month of November 1752 alone he performed two hundred
and twenty-six operations for cataract; of which one hundred and eighty-
two were successful. He died in 1762. (A)

ADDITION TO THE PRECEDING 145

We are drawn to the conclusion that the eye is
not so necessary nor so essential to our happiness
as we are inclined to believe. If the spectacle of
nature had no charms for the blind smith Daviel
operated on, what object is there to the loss of which
we should be otherwise than indifferent, after long
deprivation of sight accompanied by no pain ? The
sight of a beloved woman? I don't believe it, in
spite of the story I am going to relate. \Ve imagine
that if one had passed a long time \\ ithout seeing,
one would never be weary of looking ; but that is
not the case. What a contrast between momentary
and constant blindness !

VII. Poor patients seeking Daviel's help were
drawn to his laboratory from all the provinces of
the kingdom by his charity, and his reputation also
gathered there a large body of interested and learned
spectators. I believe Marmontel and I were present
on the same day. The patient was seated and his
cataract removed ; Daviel laid his hand upon the
eyes which he had just restored to the light. An
old woman, standing beside him, showed the liveliest
interest in the success of the operation ; she shook
in every limb at each movement of the operator.
The latter signed to her to draw near, placed her
kneeling opposite the patient, and removed his
hands. The patient opened his eyes, saw, and
cried : " Oh, it is my mother ! " I have never heard
a more piteous cry ; I seem to hear it still. The
old woman fainted, the spectators wept, and gave

their money freely.

10

146 DIDEROTS PHILOSOPHICAL WORKS

VIII. The most astonishing case of all those who
have lost their sight almost from their infancy was
Mademoiselle Melanie de Salignac, a relative of
Monsieur de la Fargue, a lieutenant-general in the
army, who recently 'died at the age of ninety-one,
covered with wounds and honours. She was the
daughter of Madame de Blacy, who is still living,
and who never ceases to regret a child who was the
deliglit of her life and the admiration of all her
acquaintances. Madame de Blacy is a woman of
high character, who is willing to confirm the truth
of my account. I write from her dictation such par-
ticulars of the life of Mademoiselle de Salignac as
did not come under my personal observation during
a friendship which began with her and her family
in 1760, and which lasted until 1763, the year of
her death.

She had a sound judgment and great sweetness
of disposition and subtlety of mind, as well as nai'vete
and freshness. When an aunt asked her mother to
help her entertain nineteen bores at dinner, she
replied, " I do not understand my dear aunt : why
be kind to nineteen bores ? I only wish to be kind
to those I love."

The sound of voices had the same attraction or
antipathy for her as facial expression for those who
see. A relation of hers, a receiver-general of finance,
unexpectedly behaved badly to her family, and she
said with astonishment : " Who would have believed
i t of such a charming voice ? " When she heard singers,
she distinguished between dark and fair voices.

ADDITION TO THE PRECEDING 14;

When people spoke to her, she judged of their
height by the direction of the sound, which came to
her from above if the person speaking were tall, and
from below if that person was short.

She was not anxious to see, and one day I asked
her the reason. " The reason," she replied, <c is that
then I should only have my own eyes, whereas now
I have the use of everybody's ; by this loss I am
always an object of interest and pity, at every in-
stant people do me kindnesses, and at ever}' instant
1 am grateful. Alas ! if I could see, no one would
trouble about me."

The errors to which sight is liable diminished it;?
value in her eyes. "I stand," she said, "at the
entrance of a long alley ; and there is a certain
object at its far end. One of my friends sees it
moving, another sees it stationary ; one says it is
an animal, another that it is a man ; and on approach-
ing it, it turns out a tree-stump. No one can tell
if the tower they see in the distance is round or
square. I brave a whirlwind of dust, while those
about me close their eyes and become ill some-
times for a whole day because they had not shut
their eyes soon enough. An imperceptible atom is
enough to cause them cruel pain." At the approach
of night she used to say that * c our reign \vas draw-
ing to a close, while hers was beginning." Living in
the dark, and accustomed to act and think during
this eternal night, insomnia, which is such a burden
to us, had no terrors for her.

She would not forgive me for my statement that

DIDEROTS PHILOSOPHICAL WORKS

the blind, to whom the symptoms of suffering are
invisible, must be cruel "Do you imagine," said
she, ' * that you hear a cry of pain as I do ? " " There
are people/' said I, " who suffer in silence.' 1 " I
believe," she said, " that I should soon discover them
and pity them all the more. "

She was devoted to reading and passionately fond
of music. "I think," said she, C I should never
tire of hearing good singing or playing ; and if this
were the only pleasure in heaven, I should not be
sorry to go there* You are right in maintaining
that music is the most impassioned of the fine arts,
not excepting poetry and oratory ; that even Racine
does not express himself as subtly as a harp, that
his music is heavy and monotonous when compared
with an instrument, and that you have often wished
to give your style the strength and lightness of
Bach's music. Music is the most beautiful language
I know. In spoken language, the better we pro-
nounce words, the more particularly we articulate
each syllable ; whereas in the language of music,
sounds of the most widely different pitch from bass
to treble and treble to bass follow one another im-
perceptibly, forming one single prolonged syllable,
which varies its inflexion and expression at every
moment. While this syllable is brought to my ear
by the melody, the harmony carries it out, without
any confusion, upon a number of instruments two,
three, four, or five perhaps which all combine to
strengthen the expression of the melody. I can
understand the music without the words sung, if the

ADDITION TO THE PRECEDING 149

symphonist is a man of genius whose music is full of
character and expression. Music is most delicious
and expressive in the silence of night.

c ' I fancy that people who see, distracted by their
eyes, cannot listen and hear as I can. Why does
the praise of music I hear seem poor and faint ?
Why can I never speak of it as I feel ? Why do I
pause in the midst of what I am saying, seeking
vainly for words expressive of what I feel ? Are
such words not invented ? I know nothing compar-
able to the effect of music but the joy I feel when,
after a long absence, 1 throw myself into my
mother's arms ; my limbs tremble, my tears flow,
and my knees totter, and 1 feel as if I should die
of joy."

She had the most delicate feelings of modesty ;
and when I asked her reason, she replied : "It is
the result of my mother's teaching, who has so
often told me that the sight of certain parts of the
body is an invitation to vice. I confess 1 have only
understood her lately, and perhaps I had to become
less innocent to do so." She died of an internal
tumour of which she never had the courage to
inform anyone.

She was extremely neat and clean In her clothes
and person, and this is the more remarkable as she
had not eyesight to assure her that she had been
successful in avoiding the vice of unclean ness and
untidiness.

When her glass was being filled, she knew by the
sound of the liquid as it fell, when it was full She

ISO DIDEROT S PHILOSOPHICAL WORKS

fed herself with surprising dexterity. Sometimes
she amused herself by standing before a mirror to
dress herself, and by imitating all the affectations of
a coquette. The mimicry was so true to life that
we laughed aloud.

From her earliest youth efforts had been made to
train her other senses, and the results were astonish-
ing. Touch enabled her to discern minute details
in shapes of objects which often pass unnoticed by
those who have the best eyesight.

She had very delicate senses of hearing and smell ;
she knew by the feeling of the air whether the
weather was cloudy or fine, whether she was walk-
ing in a square or a road, in a road or a cul-de-sac,
in an enclosed or open place, in a vast apartment
or a small room. She measured the space by the
sound of footsteps or the echo of voices. When
she had gone over a house, its plan remained in
her head, so that she would warn others of little
obstacles or dangers in their way. ** Take care/ 5
she would say, ' c the doorway here is low ; you will
find a step there."

She noticed a variety in voices which we have no
conception of, and when she had heard a person
speak once or twice she knew him for ever.

She was very little affected by the charms of
youth and by the wrinkles of age; and said she
was only charmed by the fine qualities of the heart
and intellect one of the advantages of the loss
of sight, especially for women. " My head will
never," she said, " be turned by a handsome face,"

ADDITION TO THE PRECEDING 151

She had a very trusting disposition. It was so easy,
and would have been so shameful, to deceive her.
To lead her to imagine she was alone In a room,
when this was not so, would have been the blackest
of treacheries.

She was never subject to panic, and rarely to
ennui ; for she had learnt in her solitude to be
independent of others. She noticed that at night-
fall In travelling in public vehicles people became
silent. " I do not need," she said, "to see those
whom I love to converse with." She set the
greatest value upon sound judgment, sweetness of
disposition, and gaiety. She spoke little, and was
an excellent listener. "I am like the birds, w she
said : " 1 learn to sing In the dark."

When she compared what she heard from day
to day, she was astonished at the contradictory
nature of our opinions ; praise or blame seemed to
her a matter of indifference from such inconsistent
creatures as human beings.

She had been taught to read by cut-out letters.
She had a pleasant voice, and sang with taste, and
would have gladly spent her life at concerts or
operas ; the only music she did not care for was
noisy music. She danced exquisitely, and also
played the viol very well, and owing to this talent
she was greatly in demand among young persons
of her age, to whom she taught the fashionable
dances.

She was the best beloved of her brothers and
sisters. " You see," she said, "what I owe to my

152 DIDEROTS PHILOSOPHICAL WORKS

infirmities ; people become attached to me as a
result of their kindness to me, and of my efforts to
show my gratitude and deserve their good offices.
Besides, my brothers and sisters are not jealous.
If I had sight, my heart and intellect would be the
losers. I have so many inducements to be good !
What would become of me if I were to lose the
interest that I inspire ? "

In her parents' loss of fortune, the only thing she
regretted was the loss of her masters ; but they had
so much liking and esteem for her that her music
and mathematical masters begged her to let them
teach her for nothing. She asked her mother:
" Mother, what am I to do? They are not rich,
and need all their time,"

She had been taught music by notes in relief
placed on raised lines on a large board. She read
these notes with her hand, and played them on her
instrument, and in a very short time she learnt to
play the longest and most elaborate piece.

She knew the elements of astronomy, algebra, and
geometry. Her mother, who read her Abb de la
Caille's book, would now and again ask her if she
understood it. " Quite easily," she would reply.

She declared that geometry was the science of the
blind, because it was of such universal application
and no external aid was necessary to become pro-
ficient in it. "The geometrician/' she added,
"spends nearly all his life with his eyes shut."

I have seen the maps with which she studied
geography. The parallels and meridians were made

ADDITION TO THE PRECEDING 153

of wire ; the boundaries of kingdoms and provinces
of embroidery in linen, silk, or wool of various thick-
ness ; the rivers and streams and mountains of pins"
heads of various sizes ; and cities and towns of drops
of wax of various sizes.

One day I said to her, " Mademoiselle, imagine
a cube."

"I see it."

" Place a point in the centre of the cube/ 1

"I have done so."

" From the point draw straight lines to the angles ;
into what have you divided the cube ? "

"Into six pyramids," she replied without hesita-
tion, " each having as its base one side of the cube,
and a height equal to half its height."

4 True, but tell me where you see this ? "

" In my head, as you do."

I must admit I have never been able clearly to
understand how she represented figures in her head
without the aid of colour. Was her cube formed
from memories of sensations of touch ? Had her
brain become, as it were, a hand within which sub-
stances were realised ? Had a connection between
two senses been established ? Why does this con-
nection not exist in my case, and why do I picture
nothing that is not coloured in my mind's eye ?
What is the imagination of a blind man? This
phenomenon is by no means easy of explanation.

She wrote with a pen, with which she pricked a
sheet of paper stretched on a frame divided by two
parallel and movable slats, which only left sufficient

154 DIDEROT S PHILOSOPHICAL WORKS

space between them for one line of writing. The
same method of writing served to answer her, as she
read the communication by passing her finger-tips
over the slight roughness formed on the back of the
paper by the needle or pin.

She read books printed on one side of the paper
only for her use by Prault. One of her letters was
printed in the Mercure.

She took the trouble to copy out with her needle
President Renault's Historical Synopsis?- and her
mother, Madame de Blacy, gave me this curious
document.

People will find it difficult to accept the following
fact, though I and all her family, as well as twenty
persons still alive, can vouch for it. Given a piece
of poetry of twelve to fifteen lines, if she was told
the first letter and the number of letters in each
word, she could reconstruct the poem, however odd
and far-fetched. I tried her with Colly's 2 ambigouris.
She sometimes lighted on a better word than the
original. She threaded the finest needle rapidly by
laying the thread or silk on the index finger of her
left hand and drawing this with a fine point through
the eye of the needle placed perpendicularly. She
could make all sorts of small articles edgings, bags
of all kinds, some of drawn work, and of various
patterns and colours; garters, bracelets, necklaces
made of glass beads the size of letters arranged to

1 \.Alntgt de Fhistoire de France.]

2 [CoII, Charles (1709-1783), a dramatic author who also wrote
ambigouris or nonsense verses]

ADDITION TO THE PRECEDING 155

form patterns. I am sure she would have made a
good compositor, for the greater Includes the less.

She played reversis, mediateu>\ and quadrille well.
She sorted her cards herself, and recognised each by
touch from minute peculiarities others could neither
see nor feel. In reversis she had a special place for
the ace (especially the ace of diamonds) and the
knave of hearts. The only difference In playing
with her was that the card played was named. If
the knave of hearts was in danger, a smile passed
over her face, which she could not restrain though
she realised that it was indiscreet.

She was a fatalist, and believed that our efforts
to escape our destiny only served to draw us thither.
I do not know what she thought of religion ; she
kept her opinions to herself out of consideration for
her mother, who was devout.

Lastly, I will give you her ideas upon hand-
writing, drawing, engraving, and painting, and they
are, I think, very just, as I hope you will think after
reading the following conversation between us. She
begins the dialogue :

ct If you trace on my hand with a point, a nose,
a mouth, a man, a woman, or a tree, I should be
sure to recognise them ; and if the tracing was
correct, I should hope to recognise the person whom
you had drawn ; my hand would become a sensitive
mirror, but the difference in sensibility between this
hand and the organ of sight Is Immense. I suppose
the eye is a living canvas of infinite delicacy ; the
air strikes the object, and is reflected back from the

156 DIDEROT S PHILOSOPHICAL WORKS

object to the eye, which receives a multitude of im-
pressions varying in accordance with the nature, the
form, the colour of the object, and also' perhaps
with the properties of the air which I do not know,
and of which you are equally ignorant ; and the
object is represented to you by the variety of these
sensations.

** If the skin of my hand was as sensitive as your
eye, I should see with my hand as you see with your
eyes ; and I sometimes imagine there are animals
who have no eyes, but can nevertheless see. "

"And the mirror?"

"If any bodies are not mirrors, it is by some
defect in their composition which destroys the re-
flection of the air. I think this is the more likely
as gold, silver, iron, and copper, when polished, are
able to reflect the air, while rough water and cracked
ice lose this property. Variety in sensation (and
hence in the property of reflecting air), in the
materials you employ, distinguishes the writing
from the drawing, the drawing from the engraving,
the engraving from the picture. The writing, the
drawing, the engraving, and the picture in one colour
are all monochromes."

" But if there is only one colour, we should only
distinguish that colour. "

" It seems that the surface of the canvas, the
depth of colour, and the way in which it is used,
produce in the reflection of the air a corresponding
variation to that of the objects. Don't ask me any
more, for that is all I know."

ADDITION TO THE PRECEDING 157

" To try to teach you any more would be waste
of time."

I have not described in her case all I might have
noticed if I had seen her oftener and questioned her
skilfully. I give you my word of honour that all I
have recorded is actual fact.

She died at the age of twenty-two. \Vith a
wonderful memory, and strength of mind as wonder-
ful, what progress she would have made in science
if she had had a longer life I Her mother read
history to her, and this was a task pleasant and
useful to both of them.

LETTER ON THE DEAF AND DUMB

Letter to Monsieur -

. 1751.

I AM sending, sir, to the author of The Fine Arts
reduced to a Single Principle, the Letter revised,
corrected, and augmented in accordance with the
advice of my friends ; but always with the same
title.

I grant that this title is applicable equally to the
large number of those who speak without under-
standing and the small number of those who under-
stand without speaking, and to the very small number
of those who speak and understand, and for whose
use my letter is solely intended.

I admit that it is an imitation of another Letter 1
which might be better ; but I am tired of hunting
for a better title. Whatever importance you attri-
bute to the choice of a title, the title of my letter
will remain unchanged.

I do not like quotations, and I like Greek quota-
tions least of all ; they give a learned air to a book,
which is no longer fashionable. They frighten away
readers, and if I was deciding from a publisher's

1 Letter on the Blinds/or the Use of those -who See. (D)
158

LETTER ON THE DEAF AND DUMB 159

standpoint I should leave out such scarecrows. But
I am not a publisher, so please suffer the Greek
quotations to remain where I have placed them. If
you care less for a book being good, than that it
should be read, I do not agree with you ; what I care
for is to make a good book, although it may risk
being less read.

As to the number of subjects I touch upon moving
from one to another, I would have you know, and
tell others, that this is no fault in a letter where
one is allowed to converse freely, and where the
last word of a phrase is a sufficient link to the
next

You may therefore print me, if that is all ; but
print me anonymously, if you please. I can always
admit the authorship later. I know one to whom
people would not attribute it, and another on whom
it would be certainly fathered, if it possessed some
eccentricity in its ideas, some share of imagination,
style, some temerity of thought which I should be
sorry to share, a fine display of mathematics, meta-
physics, Italian and English ; less Latin and Greek,
and more music.

See that no errors creep into the text ; a single
mistake is enough to ruin all. You will find in
Havercamp's fine edition of Lucretius in the last
book the figure I want. Take out the child which
half hides her, imagine a wound beneath the breast,
and have it copied. My friend Monsieur de S. has
undertaken to revise the proofs. His address is ...

I am, etc.

160 DIDEROTS PHILOSOPHICAL WORKS

LETTER ON THE DEAF AND DUMB

FOR THE USE OF THOSE WHO

HEAR AND SPEAK:

Which treats of the origin of inversions in language, of
harmony of style, of sublimity of situation, and of some advan-
tages which the French language has over most ancient and
modern languages, also some thoughts on expression
in the fine arts.

I HAD no intention, sir, to take credit for your
researches, and you may claim what you please in
this letter. If it happens that my ideas are similar
to yours, I am like the ivy which mingles its foliage
with the oak. I might have addressed my letter to
the Abbe de Condillac, or to Monsieur du Marsais,
who has also treated of inversions ; but you just
came to my mind, and I have made free with you,
for I am persuaded that the public will not this
time take a happy accident for a deliberate choice.
My only fear is, that I may waste your time and
snatch from you those hours which you are doubt-
less devoting to philosophy, and which you owe
to that study.

Now, in order to treat of inversions we must first
consider how languages are formed. Objects that
strike the senses are those that are first noticed, and
those which unite various qualities which strike the
senses are named first, *.*. the different objects of
which the world is composed Then the various
qualities are distinguished and named, and these form
most of our adjectives. Afterwards, these sensible

LETTER ON THE DEAF AND DUMB 161

qualities being put aside, some common quality was
observed in various objects, such as impenetrability,
extension, colour, shape, etc. , and from these abstract
and general names were formed and nearly all sub-
stantives. Gradually men became accustomed to
think that all these names represented real things ;
and the sensible qualities were regarded as simple
accidents, and thus the adjective was thought to be
subordinate to the substantive, although the sub-
stantive does not really exist and the adjective is
everything. If you are asked to describe an object,
you answer that it is a body with a surface, im-
penetrable, shaped, coloured, and movable. But
subtract all these adjectives from your definition and
what is left of that imaginary being you call a body ?
If you wished to arrange the terms of your definition
in their natural order, you would say a coloured,
shaped, extended, impenetrable, movable substance.
It seems to me that a man seeing the object for the
first time would be affected by the different qualities
in this order of terms. The eye would be first
struck by the shape, colour, and surface ; touch
would then discover its impenetrability, and eye and
touch together would discover its mobility. There
would, therefore, be no inversion in this definition,
and there is an inversion in the definition in its first
form. It follows, therefore, that if we wish to
maintain that there is no inversion in the French
language, or at least that it is much rarer than In
the learned tongues, the utmost we can say is
that our constructions in French are for the most

ii

162 DIDEROTS PHILOSOPHICAL WORKS

part uniform ; that the substantive is always, or
nearly always, placed before the adjective ; and
the verb between them. For if we consider the
question on its own merits, and ask if the adjective
should be placed before or after the noun, it will
appear that we frequently reverse the natural order
of ideas. The example I have just given is an in-
stance of this. I say the natural order of ideas ;
for we should distinguish here between the natural
order and the acquired^ or what we may term the
scientific order ; the latter is a deliberate arrange-
ment after a language is fully formed.

As adjectives usually represent sensible qualities,
they stand first in the natural order of ideas ; but
to a philosopher, or rather to philosophers who
are accustomed to regard abstract substantives as
realities, substantives will come first in the scientific
order, being, in their language, the support which
upholds the adjective. Thus of the two definitions
of a, body I gave, the first follows the scientific or
acquired, the second the natural order.

From this we may conclude that it is perhaps
owing to the peripatetic philosophy, which realised
all general and abstract entities, that we have in our
language hardly any of what we call inversions in
the classics. Our Gallic authors had much more
than we have, and this philosophy was in the
ascendant while our language was being perfected
under Louis XIII and Louis XIV. The Ancients,
who generalised less, and who studied nature more
in detail, were less monotonous in the order of their

LETTER ON THE DEAF AND DUMB 163

tongue, and the word inversion would have perhaps
astonished them. You will not raise as an objection
here, that the peripatetic philosophy is Aristotle's
philosophy, and hence the philosophy of some
portion of the Ancients, for you doubtless tell your
disciples that our peripatetic philosophy is very
different from Aristotle's.

But it is, perhaps, unnecessary to go back as far
as the creation of the world and the origin of
language to explain why inversions crept into and
were preserved in languages. It would be sufficient
to make an imaginary journey to a people whose
language one was unacquainted with ; or, what
comes to almost the same thing, to experiment with
a man who would forgo the use of articulate sounds
and try to make himself understood by gestures
alone. Such a man, who would perfectly understand
the questions put to him, would be an excellent
subject for experiment ; and from the succession of
his gestures definite inferences could be drawn as to
the order of ideas which seemed good to the early
men in order to communicate their thoughts by
gestures, and under what circumstances articulate
sounds were invented

I should give my " theoretical mute" plenty of
time to compose his replies ; and as to the questions,
I would make a point of introducing ideas whose
expression by means of gesture I should be most
anxious to learn. It would be both useful and
entertaining to multiply experiments upon these
ideas, and to propound the same questions to a

1 64 DIDEROT 'S PHILOSOPHICAL WORKS

number of persons at once. I believe that a philo-
sopher who practised such experiments with some
friends, who were intelligent men and good logicians,
would not find it a total waste of time. An Aristo-
phanes would no doubt turn it to ridicule, but what
matter ? One could say what Zeno said to his dis-
ciple : ci (pi\ocro<pla$ e-Tnfo/AeF?, vrapa<TKvaov aiJroflej/,
a>? /carayeXa&fcroVei'o?, w?, etc. If you wish to become
a philosopher, expect to be ridiculed. That is a fine
maxim, sir, and one that would elevate souls less
courageous than ours above human comment and all
frivolous considerations.

You must not confuse the experiment I suggest
with ordinary pantomime. To translate an action
and a speech into gesture are two very different
things. I am sure that there are inversions in the
language of our mutes, that each one has his style,
and that their inversions denote differences as pro-
nounced as those we find in ancient Greek and Latin
authors. But as we always most highly approve of
our own style, the discussion that would ensue after
these experiments would be of the most lively and
philosophical nature, for all our theoretical mutes,
when they had leave to use their tongues again,
would be obliged to justify not only their expres-
sion, but also the way they placed such and such an
idea in a certain order in their gestures.

This leads me to another idea that is a little alien
to the subject of my letter, but in a letter digres-
sions are allowed, especially when they lead to
useful results. My idea would be to analyse, as it

LETTER ON THE DEAF AND DUMB 165

were, a man, and to examine what he derives from
each of his senses. 1 have sometimes amused
myself with this kind of metaphysical anatomy, and
I consider that of all the senses the eye was the
most superficial, the ear the proudest, smell the
most voluptuous, taste the profoundest and most
philosophical. It would be amusing to get together
a society, of which each should have only one
sense ; there can be no doubt that all these persons
would look on one another as out of his wits, and
I leave you to judge with what reason. And yet
this is an example of what happens amongst us
every day ; we have, so to speak, only one sense,
and we judge of everything. We may remark that
this group of five persons, each possessing only one
sense, might by their faculty of abstraction have
one interest in common that of geometry, and
might understand one another on that subject, and
that alone. But to return to our theoretical mutes,
and to the questions we should put them.

If these questions were such that more than one
answer was possible, it would follow that one mute
would give one, and another mute another ; and
that the comparison between their replies would
become impossible or at any rate difficult This
difficulty suggested to me that a speech for transla-
tion from French to gesture-language would be
better than a question for experimental purposes.
The translators must be warned to avoid ellipsis, for
the language of gesture is difficult enough without
increasing its laconism by the use of this figure.

1 66 DIDEROTS PHILOSOPHICAL WORKS

By the efforts of those born deaf and dumb to
make themselves understood, we see they express
all they are able to express. I should therefore
recommend our theoretical mutes to copy them,
and, as far as is possible, to form no sentence where
the subject and the attribute with all their depen-
dencies are not expressed. In short, they would
only be allowed the choice of the order in which
they would present ideas, or rather the gestures
representing these ideas.

But there I see a difficulty. As thoughts, I
know not by what contrivance, enter our mind very
much in the form in which they appear in speech
when they are tricked up, it is possible that this
will cause some difficulty to our theoretical mutes ;
perhaps they would be tempted to imitate the
order of the words in the spoken language they are
already familiar with a temptation which assails
almost everyone who writes in a foreign language.
All of our best modern Latinists fall into French
constructions, so that perhaps our mutes' construc-
tion will not be the construction of a man who had
never had any notion of speech. What do you say ?
Perhaps this difficulty would be of less frequent
occurrence if our theoretical mutes were philosophers
or orators ; but if this obstacle arises we might have
recourse to one born deaf and dumb.

You will doubtless think this a singular way
of obtaining true notions of the formation of a
language. But pray consider, how much less far
from truth ignorance is than prejudice, and that a

LETTER ON THE DEAF AND DUMB 167

man born deaf and dumb has no prejudices with
regard to the manner of communicating his thoughts.
Consider that inversions have not passed into his
language from another, and that if he uses them it
is nature alone which suggests their use ; that he
is closely analogous to those beings people have
imagined who with no trace of education, very few
perceptions, and almost no memory, might easily
pass for two-footed or four-footed animals.

I can assure you, sir, that a translation of this
gesture language would do the translator great
credit, for not only must he have completely under-
stood the meaning and the thought, but the order
of the words of the translation must faithfully follow
the order of the gestures of the original. (To do
this a philosopher would have to question his
author, hear his replies, and represent them with
exactness ; but philosophy is not learnt in a day.)
One of these requisites would, however, facilitate
the rest ; and if the question was given with a precise
explanation of the gestures which are to compose
the answer, it would be possible to represent ges-
tures as far as possible by words. I say as far as
possible, for there are gestures so sublime that the
noblest eloquence can never translate them. Such
is the scene in Shakespeare's tragedy of Macbeth.
Lady Macbeth, walking in her sleep, advances
silently with closed eyes (Act v, Scene i), and
rubbing her hands together as if she were washing
away the stain of the king's blood she had shed
twenty years before, I know nothing in speech so

1 68 DIDEROTS PHILOSOPHICAL WORKS

pathetic as the silence and motion of this woman's
hands. What an expression of remorse !

The way in which another woman carried the
tidings of his death to her husband, who was still
uncertain of his fate, is another example of a
gesture unapproached In its vigour by the spoken
word. She went with her son in her arms to a
spot in the country which her husband could see
from the tower in which he was imprisoned ; and,
after looking for some time at the tower, she took
a handful of earth which she scattered in the form
of a cross on the body of her son, whom she had
laid at her feet Her husband understood the
sign, and starved himself to death. The sublimest
thought Is forgotten, but these actions are never
effaced from one's memory. I could make many
reflections at this point on sublimity of situation,
but they would take me too far from my subject.

Many of the fine lines in that magnificent scene
in fferaclius, where Phocas does not know which of
the two princes is his son, have been justly admired.
For my part, the passage in the scene that I prefer
is that where the tyrant turns to each of the princes
in turn, and calls them by the name of his son, and
they both remain cold and motionless :

* ' Martian^ d ce mot aucun ne veut rtpondre* " x

This cannot be put upon paper, and gesture here
triumphs over speech.

Epaminondas, at the battle "of Mantinaea, is

1 [" Martian 1 and none will answer to the word." -Corneille,
st Act iv, Scene iv.]

LETTER ON THE DEAF AND DUMB 169

mortally wounded ; the doctors tell him he will
die when the spear is drawn from his body. He
asks for. his shield, for it is dishonourable to lose the
shield in battle ; and when this is brought to him,
he draws out the spear-head himself. In the sublime
scene at the close of the tragedy of Rhodogune, the
most effective moment is certainly when Antiochus
lifts the bowl to his lips, and Timagene enters crying
" Ah, lord !" (Act v, Scene iv). What a throng of
ideas and emotions crowd upon the audience at this
gesture and this cry ! But I am digressing. To
come back to our man born deaf and mute, I know
of one who would be useful for experimental purposes,
because he is intelligent and has expressive gestures,
as you shall see.

I was playing chess one day, and the dumb man
was watching. My opponent fought me to a difficult
position, and the dumb man quite understood, and,
thinking the game was lost, he closed his eyes,
drooped his head, and let fall his arms as a sign
that he considered me checkmated, or done for.
Consider for a moment how metaphorical is the
language of gesture. At first I thought as he did ;
but as I had not exhausted the combinations, I was
in no hurry to yield, and I looked about for a way
out. The dumb man still thought there was none,
and he expressed this very clearly by shaking his
head and by putting back the lost pieces in the box.
His example induced the other spectators to discuss
the situation ; they examined it, and, after some
fruitless expedients had been tried, a successful one

170 DIDEROTS PHILOSOPHICAL WORKS

was discovered. I made use of it, and explained to
the dumb man that he was mistaken, and that I had
escaped though he did not expect me to. But he,
by pointing his finger at the spectators one after
another, and making a motion of the lips, accom-
panied by a sweeping movement of his arms in the
direction of the door and the tables, replied that it
was no credit to me to have got out of my difficulty
by calling in all and sundry to my help. His
gestures were so significant that no one could mis-
understand him, and the popular expression "all
and sundry " * occurred to many at the same time :
this expression was definitely translated by our
dumb man's gestures.

You know, at least you have heard, of a singular
machine with which the inventor proposed to give
sonatas in colour. I thought that if anyone could
appreciate a performance of ocular music, and could
judge of it without prejudice, it would be a man
born deaf and dumb. I therefore took my friend
to the house in the rue St Jacques, where the
operator and the machine with colours was exhibited.
Ah, sir, you would never guess the kind of impression
that it made on him, nor the ideas it suggested.

You see that it was impossible to explain to him
beforehand the nature and marvellous powers of the
harpsichord; and, having no idea of sound, this instru-
ment with colours could not suggest to him any
musical impressions. The purpose of the machine

1 [Consumer le fiers, le qitart ct Us peasants; literally, "the third,
the quarter, and the passers-by."]

LETTER ON THE DEAF AND DUMB 171

was as incomprehensible to him as the use of our
organs of speech. What, then, were his thoughts,
and what was the cause of his admiration for Father
CastePs coloured fans? Guess, sir, his conjectures
about this ingenious machine, 1 which very few people
have seen, though many have talked about it, and
whose invention would do honour to many of those
who ridicule it. Our deaf-and-dumb friend imagined
that the inventor was also deaf and dumb, and that
his harpsichord was the instrument by which he com-
municated with other men ; he imagined also that
each shade of colour represented a letter of the
alphabet, and that by touching the keys rapidly he
combined these letters into words and phrases, and,
in fact, spoke in colours.

You may imagine he was pleased with his own
perspicacity in finding this out ; but our friend did
not rest on his laurels ; the idea suddenly came into
his head that he now grasped what music and musical
instruments were. He supposed that music was a
peculiar manner of communicating thought, and that
musical instruments lutes, violins, and trumpets
were so many different organs of speech. You will
say that only a man who had never heard music or
a musical instrument could have happened on such
a theory. But please consider that this theory,
although obviously false to you, seemed almost
proved to a deaf-and-dumb person. When the deaf-

1 [Voltaire ridiculed the machine invented by the Jesuit CastcL
Diderot, on the other hand, returned to the idea again and again,
and ^mentions it in the Encycfotos&a. (A)]

172 DIDEROTS PHILOSOPHICAL WORKS

and-dumb man calls to mind the attention he has
observed us pay to music and to musicians, and the
evidences of joy or grief depicted on our countenances
and in our gestures as we listen to beautiful music,
and when he compares them with the similar effects
produced by speech or by visible objects, he cannot
imagine that music has no definite meaning and that
vocal and instrumental music arouses in us no distinct
impressions.

And is not this, sir, an exact symbol of the way
in which we form ideas, our theories, and, in a word,
the conceptions by which so many philosophers have
won fame? Whenever they attempt to explain
matters which seem to demand another organ which
is lacking before they can be completely understood,
they have often shown less penetration and have
wandered further from the truth than the deaf mute
I have been describing ; for, after all, if we do not
express our thoughts as distinctly by means of
musical instruments as with our lips, and if musical
notes do not convey our ideas as distinctly as speech,
yet they do convey something.

The blind man I described in the Letter on the
Blind' 1 assuredly displayed great penetration in his
conception of the use of the telescope and spectacles,
and his definition of a mirror is very remarkable ;
but there is more profundity and truth in my deaf-
mute's notion of Father CasteFs harpsichord and of
our music and musical instruments. Even if he did
not hit upon the exact truth, he hit upon a great
1 See Letter on the Blind, pp. 72-73.

LETTER ON THE DEAF AND DUMB 173

possibility. This penetration will surprise you less,
perhaps, if you fancy that everyone who walks
through a picture gallery is really unconsciously
acting the part of a deaf man who is amusing him-
self by examining the dumb who are conversing on
subjects familiar to him. This is one of the points
of view with which I always look at pictures ; and I
fancy it a sure means of divining ambiguous actions
and equivocal movements ; of being at once aware
of the frigidity and confusion of an ill-arranged
action or of conversation ; and of seeing at once,
in a scene rendered in painting, all the faults of
languid or exaggerated acting. The term " acting "
which I have just used, because it expresses what I
mean, calls to my mind another mode of studying
which I often employed and which taught me more
about actions and gestures than all the books in the
world. I used to frequent the theatre, and 1 knew
by heart most of our best plays. On the days
when I meant to examine actions and gestures I
would climb to the gallery, for the further I was
from the actors the better. As soon as the curtain
was raised, and the rest of the audience disposed
themselves to listen, I put my fingers in my ears,
much to the astonishment of my neighbours ; not
knowing my motives, they looked on me as a
madman who only came to the play to miss it. I
paid no attention to their remarks, and kept my
fingers obstinately in my ears as long as the
gestures and actions of the actor corresponded with
the dialogue which I remembered. When I was

174 D1DEROTS PHILOSOPHICAL WORKS

puzzled by the gestures I took my fingers from my
ears and listened. Ah, how few actors there are
who can stand such a test, and how humiliated the
majority would be if I were to give the world my
criticisms ! But judge of my neighbours' surprise
when they saw me shed tears at the pathetic
passages, though I had my fingers in my ears.
That was too much for them, and even the least
inquisitive began to question me. But I coolly
answered that * ' everybody had his own way of
listening, and mine was to shut my ears to hear the
better," and found some silent amusement in the
comments caused by my real or apparent eccen-
tricity and in the simplicity of some young people
who also tried putting their fingers in their ears to
hear as I did, and were surprised at their lack of
success.

Whatever you may think of my expedient, pray
consider that if, to judge correctly of intonation,
we must listen to an actor without looking at him,
it is very natural to watch an actor without hear-
ing him, if we are to judge correctly of his gestures
and action. I may add that the celebrated writer
of plays, Le Sage, the author of The Lame Devil,
The BacJielor of Salamanca, Gil Bias of Santillana,
Turcaret^ and a number of plays and comic operas
in which his son, the inimitable Montmeny, took
part, became so deaf in his old age that people had
to shout into his ear-trumpet. Yet he was in the
habit of frequenting the theatre to see his pieces
played, and could follow them almost word for

LETTER ON THE DEAF AND DUMB 175

word ; indeed, he said he was a better judge of his
plays and their action when he could no longer hear
the actors ; and I am certain, from my own personal
experience, that he was right.

In studying gesture language it appears to me
the principal idea should be presented first, because
it throws light on the rest as indicating what the
succeeding gestures refer to. When the subject of
a proposition in oratory or gesticulation is not
announced, the significance of the other gestures or
words remains uncertain. This is certainly the case
in Greek or Latin phrases, but not in the language
of gesture when properly constructed. Suppose I am
at table with a deaf-mute, and he wishes to tell his
servant to give me some wine. He first beckons to
his servant, then looks at me, then he imitates the
action of a man pouring out wine. In this sentence
it hardly matters which of the last two signs comes
first : the deaf mute, after beckoning to his servant,
may either begin with the sign representing his
order or that denoting the person whom the order
concerns ; but the position of the first gesture
cannot be altered. Only an illogical mute could
displace it. For this displacement would be as
absurd as a man speaking without knowing whom
he was addressing. As to the order of the two
other gestures, it is a matter of taste, fancy,
suitability, and harmony of style, and does not
affect the sense. As a rule, the more ideas there
are in a sentence, and the more possible arrangement
of gestures or other signs there are, the greater

176 DIDEROT S PHILOSOPHICAL WORKS

danger of falling into contradictions, ambiguities,
and other faults of construction. I do not know if
we can justly estimate a man's opinions and morals
by his writings, but I think we can form a good
judgment of his intellectual abilities from his style, or
rather his manner of constructing sentences. I can
at least say that I have never found myself mistaken
in my judgment. I have observed that every
writer whose sentences had to be completely re-
written would also have required an entirely new
brain before he was fit for anything.

But how is it possible in a dead language to use
correct constructions when there are so many pos-
sible ways of arranging words? Our language is
so simple and uniform that I venture to say it will
be easier to write and speak French correctly, if
it were to die, than it is possible to write Latin
and Greek now. How many inversions do we use
to-day in Latin and Greek which would not have
been permitted in the days of Cicero and Demos-
thenes and which the refined ears of those orators
would have rejected ?

But, people will tell me, have we not in our
language adjectives which are only used before a
substantive, and others which are only used after ?
How can our posterity learn these fine distinctions ?
Reading good authors is not enough. I agree with
you ; and if the French language dies, future savants,
who care enough for our literature to learn and write
our language, will be sure to write indifferently
blanc bonnet or bonnet blanc^ ml chant auteur or auteur

LETTER ON THE DEAF AND DUMB 177

m chant, homme galant and galant homme, and a vast
number of similar phrases which would make non-
sense of their writings were we to rise up to read
them, but which would not prevent their ignorant
contemporaries from exclaiming when they read some
such piece : {< Racine did not write more correctly/'
or " That is just like Despreaux ; Bossuet could not
have said it better ; this prose has the music, the
force, the elegance and ease of Voltaire's. " But if
a limited number of difficulties may cause those who
come after us to stumble, what are we to think of
our modern Greek and Latin authors and of the
admiration they obtain?

In talking to a deaf-mute it is found to be almost
impossible to describe to him indefinite portions of
quantity, number, space, or time, or to make him
grasp any abstract idea. One can never be sure that
he realises the difference in tense between I made,
I have made, I was making, and / should have made.
It is the same with conditional propositions. If,
then, I was right in saying that at the origin of
language men first named the principal objects of
sense, such as fruit, water, trees, animals, serpents,
etc., and then named passions, places, and persons,
qualities, seasons, etc., I may add that signs for
periods of time and tenses were invented last of all.
I imagine that for long centuries men had no other
tenses than the present indicative and the infinitive,
which became, according to the circumstances,
either a future or a past.

I am supported in this conjecture by the present

12

i/8 DIDEROT'S PHILOSOPHICAL WORKS

state of the lingua franca the language spoken by
the various Christian nations trading with Turkey
and the Levant ports. I believe it is the same to-
day that it has always been, and that it will never
develop. Its base is a corrupt Italian. The present
infinitive is used for every tense, and its meaning is
modified by guessing and by the other words of the
sentence. Thus, / love thee, I was loving thee, I
shall love thee, are all in lingua franca, "miamarti."
All have sung, Let each one sing, All will sing, are
' ' tutti cantara. " / wish, I was wishing, I have
'wished, I should like to marry you, are "mi voleri
sposarti* "

I imagine that inversions have crept into a
language and been preserved in it because gesture
language gave rise to the language of oratory, and
that they naturally retained the position thus as-
signed to them in the sentence. I also think that,
for the same reason, as tense was not accurately
defined even after conjunctions were formed, some
languages, like Hebrew, which has no present or
imperfect, did without certain tenses. They said
Credidi propter quod locutus sum instead of Credo et
ideo loquor: I Jiave believed, and therefore I have
spoken, instead of / believe, and therefore I speak.

In other languages the same tense had two
different meanings, as in the Greek language, where
the aorist is at one time expressive of the present,
at another of the past. Let me quote as an illustra-
tion there are many others a passage in the
EncJuridion, which is perhaps not so familiar to you

LETTER ON THE DEAF AND DUMB 179

as some. Epictetus says : QeXovcri KOL avrol <J>L\O-
<ro<pelv. A.v6p<*)7Ti TTptoTOv ex/ovce^cu, otrolov <TTL TO
7T/>ay/xa ' efra KOL Trjv a-eavrov <j>vviv /cara/^aSe, el Svvaa-ai
ftaa-Tdarai. TLevTaOXog etvat f3ou\et, rj TraXai 0-7-779 ; tSe
a-eavrov TOVS /3paxiova$, TOI/? fjLrjpovs, Ttjv 6<r<f>vv /cara-
jj.aQe (ch. xxix). A close translation is : " These
men also wish to be philosophers ; O man, first have
learnt what it is that you wish to be, have studied
your strength and the burden, have considered your
arms and thighs, have tried your loins if you intend
to be a pentathlete or a wrestler." This can be
much better translated by substituting the present
for the first and second aorists ; thus : "These men
also wish to be philosophers. Man, first learn what
it is you wish to be ; .study your strength, and the
burden ; consider your arms and thighs ; try your
loins if you intend to be a pentathlete or a wrestler. "
The pentathlete, as you know, was one who intended
to enter for all the gymnastic exercises.

I consider these eccentricities of tense as the
result of the original imperfection of languages
and the traces of their original rudimentary state,
against which common sense (which does not allow
one and the same expression to render different
ideas) vainly strove in after times. It was in vain ;
the usage was fixed, and use won a victory over
common sense. But there was, perhaps, not a single
Latin and Greek author who was aware of this
defect. I go further, and .maintain that every
Greek and Latin author probably imagined in their
speeches and writings that their words exactly

i8o DIDEROTS PHILOSOPHICAL WORKS

followed the order of their ideas. But evidently it
was not so. When Cicero begins his oration pro
Marcello by Diuturni silentii, Patres conscripti, quo
eram his temporibus usus, etc., we can see that he
was thinking of something before his c ' long silence "
an idea which was to follow and break in upon
his "long silence," and which caused him to say
Diuturnt silentii instead of Diuturnum silentium.
This remark upon the inversion of the beginning of
this oration applies equally to all cases of inversion ;
as a rule, in all Greek and Latin periods, however
long they may be, we observe at once that the
writer had some reason for preferring to use certain
cases, and that there was not the same inversion in
his ideas as in the order of his words. In the above
sentence of Cicero's, what made him use the genitive
case in Diuturni silentii^ the ablative in quo y the
imperfect tense m eram, and so on, was the order
of ideas pre-existing in his mind which did not
coincide with the order of the words an order he
obeyed unconsciously, from a long practice in trans-
position. Why should Cicero not have used in-
version unconsciously, since we, who think our
language follows the natural order of ideas, do so
too? I was therefore justified in distinguishing
between the natural and the acquired or scientific
order of ideas and signs.

You thought, sir, it might be argued, that there
was no inversion in that period of Cicero's ; you are
mistaken, but two considerations which have escaped
your notice will convince you. The first is, that as

LETTER ON THE DEAF AND DUMB 181

inversion proper, or the acquired, scientific and gram-
matical order, is really an order in words which does
not correspond to the order in ideas, what is inver-
sion for one is not so for another, for different minds
may put their words in different order. For in-
stance, in the sentence serpent em fuge I would ask
you which is the principal idea. You may say that
it is the serpent, but another will say it is flight ;
and both ot you may be right. A timid man thinks
only of the serpent ; but the man who fears my
danger more than he fears the serpent thinks only
of my flight : one is overwhelmed by terror, the
other gives me warning. The second thing I would
remark is, that when we are presenting a series of
ideas to others, and the main idea we wish to im-
press upon them is not the one by which we our-
selves are most impressed (because we and our
hearers are differently situated), it is this former
idea which we should present first, and such an in-
version is but a matter of oratory. Let us apply
these observations to the first period of the oration
$ro Marcello. I picture to myself Cicero mounting
the tribune to speak to the people ; and I see that
the first idea that will strike his audience is that it is
a long time since he spoke to them ; hence diulurni
silentii, his prolonged silence, is the first idea he must
present to them, although the principal idea in his
mind is rather hodiernus dies finem attulit ; for the
orator's main preoccupation is the speech he is about
to make, not his past silence. I notice another reason
for the use of the genitive case in diuturni silentii ;

1 82 DIDEROT 'S PHILOSOPHICAL WORKS

the audience could not realise the fact of Cicero's
prolonged silence without seeking for the cause of
it, and why he was at last breaking it. Now the
genitive, being a case incomplete in itself, induces
the minds of his hearers to travel onwards to meet
the ideas that the orator could not present at once.

These are, sir, the remarks upon the passage in
question which you might have made. I am sure
Cicero would have arranged this period quite
differently, if, instead of speaking at Rome, he had
been suddenly transported to Africa to plead at
Carthage. This will show that what was not an
inversion for Cicero's hearers would be and must
be one for the orator himself.

But to go a little further: I hold that when a
phrase only contains very few ideas, it is very diffi-
cult to determine the natural order of these ideas in
relation to the speaker ; for if they are not all pre-
sented at once, their succession is so rapid that it
is often impossible to decide which strikes us first.
Who can say if the mind cannot embrace a certain
number at one and the same instant ? Perhaps you
will call this paradoxical ; but let us examine to-
gether how the article 7#V, tlle y le came to be intro-
duced into Latin and into our language. It will
not be a long .or difficult matter, and may induce
you to accept a position that you find distasteful
at present.

Let us first transport ourselves to the period when
Latin adjectives and substantives which denoted the
qualities perceived by sense in various natural objects

LETTER ON THE DEAF AND DUMB 183

were almost all invented, but when no expression
had yet been found for those intellectual subtilties
which philosophy has even to-day much difficulty in
distinguishing. Next imagine two hungry men, one
of whom could see no food, while the other stood
beneath a tree so very tall that he could not reach
its fruit. Their sensations make both these men
speak ; the first would say : / am hungry, I would
like to eat ; and the second, What beautiful fruit /
/ am hungry ', I would like to eat. Now, it is obvious
that the former has adequately expressed in words
all that passed in his mind ; while the latter has left
something unexpressed a portion of his thought
must be supplied. The expression I would like to
eat, when no food is to be seen, applies generally to
all food that could appease hunger ; but the same
expression is limited in its application, and refers
only to a fine fruit when that fruit is to be seen.
Thus, though they both said 7 am hungry, I would
like to eat, the man who exclaimed "What a fine
fruit ! " returned in thought to this fruit, and I make
no doubt that if the article le had been in use he
would have said : WJiat fine fruit ! I am hungry ;
I would like to eat this (or this I would like to eat).
The article le or celuim this case and in other similar
cases denotes that the mind reverts to an object
which it had previously considered, and the inven-
tion of this symbol is, I think, a proof of the
progress of the mind.

Do not raise difficulties about the position this
word ought to occupy in the sentence in accordance

1 84 DIDEROTS PHILOSOPHICAL WORKS

with the natural order of ideas, for though these
statements, What fine fruit ! I am hungry, I would
like to eat that, are each expressed by two or three
words, each only denotes a single notion ; the mid-
most sentence, I am Iwngry, is expressed in Latin
by a single word esurio. The fruit and its quality
are perceived at the same time ; and when a Roman
said esurio he only imagined he was expressing a
single idea. / would much like to eat that are only
modes of single sensation. / denotes the person
who experiences it ; would like to eat, the desire and
the nature of the sensation experienced ; much, its
intensity ; it, the presence of the desired object But
in the mind there is not the successive development
we observe in speech ; if it had twenty mouths, and
each mouth able to say a word, all the above ideas
would be expressed at once. This could be ex-
cellently executed on Father Castel's harpsichord,
if our dumb friend's theory were in practice and
each colour combined to form words. No tongue
would approach it in the rapidity of its speech.
But as we have not many mouths, people have
attached several ideas to a single term. If there
were more of these vigorous terms, instead of the
tongue panting after the mind, such a number of
ideas could be expressed at once that the mind
would lag after the tongue which hastened in advance
of it. What would then be the fate of inversion,
which implies a disintegration of many simultaneous
mental impressions and a number of words? Al-
though we have few words equivalent to a long

LETTER ON THE DEAF AND DUMB 185

speech, we have some, and Greek and Latin are
full of them ; they are at once understood when
used, and this is a proof that the mind experiences
a multitude of sensations, if not simultaneously,
yet in such rapid succession that it is impossible
to distinguish their order.

If I had to explain this system of the human
understanding to one who found it difficult to grasp
abstract ideas, I should say, "Consider man as a
walking clock ; the heart as its mainspring, the
contents of the thorax as the principal parts of the
works ; look on the head as a bell furnished with
little hammers attached to an infinite number of
threads which are carried to all corners of the clock-
case. Fix upon the bell one of those little figures
with which we ornament the top of our clocks, and
let it listen, like a musician who listens to see if his
instrument is in tune : this little figure is the soul.
If many of these little threads are pulled at once,
the bell will be struck several times, and the little
figure will hear several notes simultaneously. Imagine
that there are some of these threads that are always
being pulled ; and just as we only notice the noise
of Paris by day when it ceases at night, we shall be
unconscious of some sensations which are continuous,
such as of our existence. The mind, especially in
health, is unconscious of its own existence, unless
it deliberately examines Itself. When we are well,
we are unconscious of any part of our body ; and if
any part draws attention to itself by pain, we are
certainly not well ; and if it is by a pleasurable

186 DIDEROTS PHILOSOPHICAL WORKS

sensation, it is by no means certain that we are
the better for it."

I could pursue my analogy still further, and add
that the sounds produced by the bell do not die
away at once, but have some duration ; that they
produce chords with the sounds that follow, and
the little figure that listens compares them, and
pronounces them harmonious or dissonant ; that
memory, which we need to form opinions and to
speak, is the resonance of the bell ; the judgment,
the formation of chords ; and speech, a succession
of chords. It is not without reason that some brains
are said to be "cracked," like a bell. And is not
the law, which is so necessary in a series of harmonies,
of having at least one note common to the chord
and that following it, also applicable? Does not
this common note resemble the middle term of a
syllogism ? And what else is the likeness we observe
in certain minds but the result of some freak of
nature by which two intervals are marked, one a
fifth and the other a third, in relation to another
note? By this fertile analogy, and with all the
madness of Pythagoras, I might demonstrate the
wisdom of that Scythian law which prescribed one
friend as a necessity, permitted two, and forbade
three. Among the Scythians, I might say, a man
was "out of tune" if the note which he gave forth
found no harmonic among his fellow-men ; three
friends would make a perfect accord ; while a fourth
superadded would be but a repetition of one of the
former three, or would introduce a discordant note, '

LETTER ON THE DEAF AND DUMB 187

But enough of this language of metaphor, which
at best is but fitted to amuse and arrest the volatile
mind of a child ; let us come back to philosophy,
which requires arguments and not analogies.

When people examined the various utterances
called forth by the sensations of hunger and thirst,
they observed that the same terms were used to
express different notions ; and the symbols you y he,
me, the, and many others, were invented for the sake
of precision. A mental state during an indivisible
moment of time was expressed by a number of words
which divided the complete expression into a number
of parts ; and because these words were uttered one
after another, and were only understood in the order
they were spoken, it was thought that the sensations
they expressed were experienced by the mind in the
same order. But this is not the case. Our mental
state is one thing, our analysis of it quite another.
This is so, whether we analyse it to ourselves or to
others. The complete and instantaneous perception
of this state is one thing ; the detailed and continuous
effort of attention we make to analyse it, state it,
and explain it to others, another. Our mind is a
moving scene, which we are perpetually copying.
We spend a great deal of time in rendering it faith-
fully ; but the original exists as a complete whole,
for the mind does not proceed step by step, like
expression. The brush takes time to represent
what the artist's eye sees in an instant In the
growth of language, decomposition was a necessity ;
but to see an object, to admire it, to experience an

1 88 D1DEROTS PHILOSOPHICAL WORKS

agreeable sensation, and to desire to possess it, is
but an instantaneous emotion, rendered in Greek
and Latin by a single word. This word once uttered,
all is said and understood. Ah, how our understand-
ing is modified by words, and how cold a copy of
reality is the most vigorous utterance !

Les ronces degouttantes
Portent de ses cheveux les depouilles sanglantes. 1

This is one of the most life-like pictures I know,
but yet how far is it from my imagination I

I beg of you, sir, to consider these points if you
wish for a juster notion of this complex question
of inversion. For my part, I am fitter to gather a
cloud than to scatter it, to suspend my judgment
than to give a verdict ; and I am going to prove
that if the paradox that I have just advanced does
not hold good, and if our mind does not allow of
several perceptions at one and the same time, it
would be impossible to think and speak ; for
thought and speech consist in the comparison ot
two or more ideas. Now, how is it possible to
compare ideas which are not both at once present in
the mind ? You allow that we can experience more
than one sensation at a time ; for example, we can
perceive the colour and shape of a body at the same
time ; why not also abstract ideas ? Does not
memory employ two ideas present at the same time
in the mind the actual idea, and the remembrance
of the former ? For my part, I think that is why a
good judgment and a good memory are rarely found

1 Racine, Ph^dre l Acte v, Scfcne vu

LETTER ON THE DEAF AND DUMB 189

together. A good memory presupposes a great
facility in embracing various ideas at one and the
same moment or in rapid succession ; and this gift
interferes with the tranquil examination of a small
number of ideas which the mind ought to contem-
plate with fixed attention. A mind stored with a
huge variety of things is like a library of odd
volumes ; it is like one of these German compila-
tions bristling with Hebrew, Arabic, Greek, or
Latin quotations put together without judgment or
taste ; which are ponderous as it is, and which will
grow more and more ponderous, and grow none the
better ; a store full of analyses and appreciations and
ill-digested works, and shops of mixed goods where
the memorandum alone is in order ; a commentary
where we scarcely ever find what we want, but
often what we don't want, and almost always what
we want is lost in a heap of rubbish.

It follows from the foregoing statements there
is not, and perhaps there cannot be, inversion in the
mind, especially if the object contemplated be an
abstract one ; and though a Greek may say : w/ciycrcu
okufj.'Tna. 6e\eis*, /cayo>, vrj rov$ 8eov$' KOJJ^SOV yap
<TTIV (Epictetus, Enchiridion^ ch. xxix) and a
Roman Honores flurimum valent apud prudentes , st
sibi collates intelligant^ French syntax and common
sense find this Greek and Latin syntax embarrassing,
and say without any inversion : You would like
to belong to tlie French Academy? So should I ;
for it is an honourable distinction, and the wise man
may value a distinction which he feels he deserves.

190 DIDEROTS PHILOSOPHICAL WORKS

I would not therefore care to maintain without
distinction the general statement that the Romans
did not use inversion, whereas we do. I should
merely say, if instead of comparing our sentence
with the order of ideas we compared it with the
order of the inversion of words, with gesture-
language, for which spoken language has been
gradually substituted, it would appear that we
invert ; and we use more inversions than any other
nation in the world. But if our construction is com-
pared with that of a mind influenced by Greek and
Latin syntax, we have the fewest possible inversions.
We express things In French in the order the mind
has to consider them, whatever the language.
Cicero, if we may say so, followed the French
order before obeying the Latin.

It follows that, since the communication of
thought is the principal object of a language,
French is of all languages the best organised, the
most precise, and the most excellent, for it retains
less than any other the negligences, or what I may
call the lispings, of the childhood of the race : in
other words, by having no inversions we have gained
in clearness and precision, which are essential
qualities in writing ; but on the other hand we have
lost in warmth, in energy, and in eloquence. I may
add that the orderly and didactic movement of our
language makes it peculiarly suitable for science ; but
the Latin, Italian, and English languages, which
allow of inversion, are more suited for literature.
We can express the intellect better than any other

LETTER ON THE DEAF AND DUMB 191

nation, and common sense will choose French for
its utterances ; but imagination and the passions
will prefer the ancient tongues, and that of our
neighbours, to ours. French should be the language
of society and of the schools of philosophy ; Greek,
Latin, and English, the language of our lecture-
halls, pulpits, and theatres ; but if truth return to
earth, I believe French would be her chosen speech,
while Greek, Latin and the other tongues will be
the language of fables and falsehoods. French is
the language for teaching, enlightening, and con-
vincing ; Greek, Latin, Italian and English for
persuading, stirring the passions, and hoodwinking ;
talk Greek or Latin or Italian to the multitude, but
talk French to the wise.

Another drawback to languages with inversions
is that the attention of the reader or hearer is
taxed. How many cases, tenses, and termina-
tions are there not to bear in mind in a long
Greek or Latin sentence ? It is almost incomprehen-
sible until one reaches the last word ; while in French
there is none of this strain, and we can understand
as we go along. Ideas in our language are presented
in the order they presented themselves to the mind,
whether the mind be Greek or Latin. La Bruyere
is less fatiguing to read in the long run than Livy,
though the former is a profound moralist, the latter
a simple historian ; but the historian sets his
sentences and phrases so artificially, that we are
continually removing them from their sockets, and
restoring them to their clear and natural order,

192 DIDEROTS PHILOSOPHICAL WORKS

and Insensibly weary of the toil, just as the strongest
arm wearies of a small weight which is constantly
carried. So, take it all in all, our pedestrian
language has the advantage of utility over the
others.

But there is a motive which both in French and
in the ancient tongues disturbs the natural order of
ideas, and that is the desire for harmony of style a
desire which is now become so imperative that we
are ready to sacrifice a great deal to it. For we
must distinguish between three phases that all
languages pass through when they have left that
earliest stage when they were merely a confusion of
cries and gestures which we may call the animal
phase. These three phases are birth, development,
and perfection. The newly-born language was
made up of words and gestures in which adjectives -
without gender or case and verbs without tenses and
not governing cases preserved the same terminations
throughout. In the developed language there were
words, cases, genders ; and verbs were conjugated
and governed cases. In fact, there were all the
necessary signs for expressing thought, but nothing
more. In the perfected language, beauty was
required ; for people thought the ear must be
pleased as well as the mind. But as the subsidiary
is often thus set before the principal thing in the
sentence, the order of ideas is often disturbed to
procure this harmony of style. This is what Cicero
has done in part of his opening period in the pro
Mar cello \ for the first Idea that "he should have

LETTER ON THE DEAF AND DUMB 193

presented to his hearers, after that of his long
silence, was the reason for this silence. He should
therefore have said : Diuturni silentii, quo, non
timore aliquO) sed partim dolor e, partim verecundia,
eram his temporibus usus> fineni^ Jiodierxus dies
attulit. Compare this sentence with the original, and
you will find no reason why it should not have been
used by him, except that of harmony. Another
instance is the great orator's phrase, Mors terrorque
civium ac sociorum Romanorum* where it is evident
that the natural order required terror morsque.
There are a number of other examples I could quote.
This leads us to the question whether the natural
order should be sacrificed for the sake of harmony.
I think this is permissible when the inverted ideas
are so close to one another that they strike the ear
and mind almost at the same moment ; just as we
transpose the fundamental bass into a higher clef
to make it more tuneful, although the transposed
bass will only be agreeable so long as the ear can
distinguish the natural progressions of the funda-
mental bass which suggested it. Do not think from
this remark that I am a great musician ; it is only
two days ago that I began to be one ; but you know
how one likes to parade some new accomplishment.
I think we might discover several analogies between
musical harmony and harmony of style. When, for
instance, we are about to describe some great or
wonderful events, the harmony of style must be
sacrificed or at least disturbed. So we say:

1 " The death and panic of the Roman citizens and their allies."

13

I 9 4 DIDEROTS PHILOSOPHICAL WORKS

Magnum Jovis incrementitml

Nee brachia longo

Margin* terrarum porrexerat Amphitrite?
Ferte titiferrum, date tela, scandite muros*

Vita quoquc omnis

Omnibus e nervis atque ossibus exsolvatur*
Longo sedproximus intervallo?

In a similar manner in music we must sometimes
shock the ear in order to surprise and please the
imagination. We may also observe, that though
these licences in the order of words are only per-
mitted for the sake of the harmony of style, licences
in harmony, on the other hand, are chiefly taken to
arouse and give rise in the most natural order to
the ideas which the musician wishes to express.

In speech we must distinguish between thought
arid expression ; if thought is expressed with purity,
clarity, and precision, this is quite sufficient for
ordinary conversation ; if you add to these a certain
distinction in the use of words and a certain rhythm
and harmony, you will have a style well fitted for
an orator, but you will still be far removed from
poetry, especially from the grand style of the epic
and the ode. There is a spirit in the poet's lan-
guage which moves there and breathes life into each
syllable. What is this spirit ? I have felt its pres-
ence, but find it difficult to describe. I may say
that it states and paints objects at the same time ;

1 Virgil, BucoL, Eclog. iv, v. 49.

2 Ovid, Afefam., lib. i, vv. 13-14.

3 Virgil, Mncid, lib. ix, v. 37.

4 Lucretius, De rerum nat., lib. i, vv. 810-811.

5 Virgil, ^neid^ lib. v, v. 320.

LETTER ON THE DEAF AND DUMB 195

it appeals not only to the understanding, but to the
soul which it stirs and the imagination that sees
and the ear that hears. The lines are not merely
a chain of vigorous words which express the thought
both forcibly and nobly, but a series of hieroglyphs,
one after another, which picture the thought to us
vividly. I might say that all poetry is symbolic.

But it is not everyone who can understand these
symbols. In order to feel their full force we must
be, as it were, in the creative mood. The poet says :

JSt des fleuves franfaises les eaux ensanglantses
Ne portaient que dts marts aux mers epouvaniees^

Does everybody appreciate the value of the first
syllable of the word portaient, which paints us the
waters swollen with corpses and the stream choked,
as it were, by this obstacle? And in the second
syllable of the word, does everyone see the mass of
waters and dead bodies subsiding and moving out
to sea ? The terror of the sea is brought before us
all in the word tpouvanttes, but the stress laid on
the third syllable brings before me the vast extent
of the ocean. Again, the poet says :

Soupire^ 'etend les bras, ferme fosil tt fend&rt?

All exclaim, ' ' How fine ! " but it is not by counting
the syllables on one's fingers that we can judge how
fortunate the poet was, when expressing a sigh, to
have such a word as soupire with its long-drawn
sound. We read t end les frras, but we hardly realise

1 Voltaire, Hcnriade, chant ii, v. 357.

2 Boileau, Lutrin, chant ii, v. 164.

196 DIDEROTS PHILOSOPHICAL WORKS

how the impression of length and lassitude is ex-
pressed by the long monosyllable bras y and the
* * outstretched arms " fall so reposefully on the ear
at the close of the first hemistich of the line. Do we
notice the rapid movement of the eyelid in ferine
Vml and the almost imperceptible change from
wakefulness to sleep at the close of the second
hemistich ferine fceil et s'endoitt

The cultivated reader will of course observe that
the poet has four actions to represent, and that his
line is divided into four parts ; that the two last
actions are closely interrelated, and that they have
scarcely an interval between them ; and that the two
last and corresponding parts of the line are also
closely linked, united as they are by the rapidity
of the movement of the penultimate part and by a
conjunction ; that each of the actions takes only its
proper proportion of time in the verse ; and that as
all four actions are comprised in this small space,
the poet has expressed their rapid succession in
nature. That is the kind of problem that the poet's
genius solves unconsciously ; but do his readers
realise his skill? Certainly not; and I shall not
therefore be surprised if those readers of Boileau
(and there are many) who have not understood the
meaning of his symbols laugh at my commentary,
and, remembering the Chef-d?ceuvre <pun inconnu^
treat me as a visionary.

1 Le chef-tfcrunre d*un inconnu, ccoec des remarques savantes, par
M. le docteur Chrysostome Mathanasius, La Haye, 1714. This little
jeu flf esfrit was the work of Themiseul de Saint llyacinthe, S'Grave-

LETTER ON THE DEAF AND DUMB 197

I used to think, like everybody else, that one poet
could translate another, but I have found out my
mistake. The thought can be rendered, and perhaps
by good fortune the equivalent expression. Homer
said : eK\aygav S ap otcrrol (Iliad, Cant i, v. 46)
and lela sonant humeris is Virgil's version (^Eneid y
lib. iv, v. 149). That is something, but not all ;
the suggestive symbolism, the subtle hieroglyphs
which pervade a long description, and which depend
on the distribution of long and short syllables in an
unaccented language and on the distribution of vowels
between consonants in all languages, disappear even
in the best translation.

Virgil writes of Euryalus stricken by a mortal

wound :

Pulchrosque per artus

It cruor^ inque humeros cervix collapsa recumMt :
Purpureus vduti quum flos^ sucdsus aratro,
Languesdt moriens ; lassovc papavera collo
Demisere caput^ pluviam qitum forte gravcuitur^

I should just as soon expect these lines to have
sprung from letters scattered at haphazard, as that

sand, Sallengre, Prosper Marchand, and others, who wrote admiring
comments in all languages upon the words of a song beginning :
" L/autre jour Colin malade

Dedans son lit
D'une grosse maladie

Pensant mourir."

The authors were ridiculing German scholarship. (A)
d, lib. ix, w. 433-437

Blood trickles o'er his limbs of snow,
His head sinks gradually low ;
Thus severed by the ruthless plough,

Dim fades a purple flower :
Their weary necks so poppies bow
O'erladen by the shower.

(Trs. Conington.)

198 DIDEROT S PHILOSOPHICAL WORKS

a translation could render all the suggestive beauties :
the gush of blood, it cruor ; the drooping head of the
dying lad, cervix collapsa recumbit \ the sound of
the scythe, 1 succisus ; the languor of death, languescit
moriens ; the softness of the poppystalk, lassove
papavera collo ; and the demisere caput zxidgravantur
suitably complete the picture. Demisere is as soft
as the stalk of a flower ; gravantur is as heavy as
its cup heavy with rain ; collapsa expresses effort
and relapse. The same symbolic suggestion is to be
found in papavera ; the first two syllables show the
poppy with head erect, and in the last two it droops.
All these pictures are compressed in these four lines
of Virgil. You have been affected by the happy
parody in Petronius 2 of Virgil's lassove pap aver a collo
applied to the exhaustion of Ascyltus when he quits
Circe ; and you would not have so keenly appreciated
Petronius' use of the phrase if you did not recognise
in it a faithful picture of the plight of Ascyltus.

This analysis of Virgil ought to be enough for
me ; and after drawing attention to more beauties
than are perhaps to be found in the original
certainly more than the poet deliberately thought
of, my imagination and taste ought to be completely
satisfied. No, sir ; I am about to expose myself to
two criticisms of having seen beauties that were

1 Aratrum does not mean a scythe, but the reason for this rendering
will appear a little further on. (D)

2 Ilia solo fixos oculos aversa tenebat

Nee prius incepto vultum sermone movelur
Quam lentae salices, lassove papavera collo.

Satyricon. (Br)

LETTER ON THE DEAF AND DUMB 199

not there, and criticised defects that were also non-
existent. Now for it. I think the word gravantur
is a little too heavy for the light poppy flower, and
the aratro following succisus does not to me complete
the suggestive picture. I am convinced Homer
would have concluded his line with a word that
would have continued the sound of a cutting imple-
ment, or have depicted to my imagination the soft
drooping of a flower.

It is the recognition of, or rather the vivid feeling
for these symbolic expressions which are lost on the
ordinary reader, that discourages men of genius from
attempting a translation. That is why Virgil said
that it is as difficult to take a line from Homer as
to snatch a nail from the club of Hercules. The
more a poet uses this symbolism, the more difficult
he is to translate, and Homer is full of such suggestive
symbols. Let me quote those lines where Jupiter
with his dark brows confirms to ivory-shouldered
Thetis his promise to avenge the injustice done to
her son :

*H S /cat KvaverfVLV r* o^pvcri vevcre
"Aju./3pocr4<u 8* cipa ^olraj. 7Tpp<ikravTO
K/oaros owr* adavdroLo ' p.eyav 8" cXcXefcp *QXvfjurov.

Iliad, i, 528-530.!

How many images there are in these three lines !
We see Jupiter's frown in eV otypvcrt, In vev&e K/oowW,
and especially in the happy repetition of the letter
k "in ?, teat icvaverja-w ; his flowing loclcs are expressed
in eTrefiptocravTO avaicro?l the immortal head of the

1 * He spake and nodded with his dark-hued brows ; and the ambrosial
locks from his immortal head shook ; and great Olympus trembled."

200 D IDE ROTS PHILOSOPHICAL WORKS

god is majestically lifted by the elision of OTTO in
Kparos rV aQavdroto ; the shaking of Olympus is
expressed in the two first syllables of eXeXtgev ; the
size and sound of Olympus in .the last syllables of
fj.eyav and \\igev and in the last word where all
Olympus trembles with its close.

The line which I have just written is the feeble
rendering of two symbols one from Virgil, the other
from Homer ; one of shock, the other of fall :
And all Olympus trembles with its close.

..... Procumbit humi bos. 1

It is the repetition of the letter / in \e\igev
*Q\vfj.Trov which gives the idea of trembling and
shock. The same repetition of fs is found in my
" Olympus trembles " ; but as the Fs are not so close
together as in .Xe\igv 3f O\vju.7roi> y the shaking is less
rapid and also less like the movement of frowning
brows. " Trembles with its close" represents pro-
cumbit humi bos fairly well, though the last word
of my line is less heavy and emphatic than bos y
which is a greater contrast with the word humi than
close is with the short words immediately preceding
it. Virgil's monosyllable is thus more isolated than
mine, and the fall of his ox heavier and more com-
plete than the close of my line.

An observation I may make here, which is just as
apposite as the, speech of the Emperor of Mexico .in
the chapter about coaches in Montaigne, 2 is that
people had a singular veneration for the ancients,

1 .'Knfirf lib. v, v. 481. 2 Essais, liv. iii, ch. vi.

LETTER ON THE DEAF AND DUMB 201

and a great fear of Boileau, when they asked him
if the three following lines of Homer,

Zeu irdrep, dAAo, cru pvcrcu {JIT yepos vtas *A^ata>j/ *
TLofya-ov S* aWp-qv, Sos S* o^OaXj^OifTLV iBecrQai '
'Ev Se <at /cat oAccro-oi/, 7ret vv roi cuaSev OTJTW?.

(Iliad, Cant, xvii, v. 645.)

were to be interpreted as Longinus 1 had inter-
preted them, and as Boileau and La Motte had
translated them, or not.

These are the true feelings of a warrior, cry
Boileau 2 and the orator Longinus. He does not
ask for his life to be spared, for a hero is above
such a weakness ; but as he sees no opportunity of
showing his courage in the midst of darkness, he is
provoked at not 'fighting ; he therefore is anxious to
ask for daylight, so that his end may at least be
worthy of him, even if he has to fight with Jupiter
himself.

Well, sir, I shall answer Longinus and Boileau : it
is not a question here of the feelings of a warrior,
nor what he would say in the circumstances in
which Ajax is placed (Homer apparently knew these
things as well as you), but of translating these lines
of Homer correctly. And if it turns out that there
are none of these sentiments you praise in these
lines, what becomes of your praises and reflections ?
What must we think of Longinus, La Motte, and
Boileau, if we find they have invented and inserted

1 Treatise on the Sublime^ section ix.

2 Grand Dieu I chasse la nuit qui nous couvre les yeux
Et combats contre nous a la clart des cieux.

Boileau, translating the Treatise on the Sublime ; ch. vii.

202 DIDEROT S PHILOSOPHICAL WORKS

Impious boasting in the place of a sublime and
touching prayer ? Now, this is just what has hap-
pened. Read these three lines of Homer as many
times as you please, and you will find nothing but
" Father of gods and men, drive away the dark-
ness which covers our eyes, and, since you have
resolved to slay us, let us die in the light."

And must we thus without a struggle die ?
Great God, drive off the darkness from our eyes,
And let us perish under open skies.

This translation does not give the pathos of
Homer's lines, but at any rate it avoids the nonsense
of La Motte and Boileau.

There is no defiance of Jupiter here, nothing but
a hero ready for death, if it be the will of Jupiter,
and asking no grace but to die fighting. Zeu Wrep,
Jupiter , Pater ! Is that how the philosopher Men-
ippus addresses Jupiter?

At the present day, when we are no longer at the
mercy of the lines of the redoubtable Boileau, and
the philosophic spirit has taught us to see in things
only what is actually there and to praise only what
is truly beautiful, I appeal to the learned men and
men of taste, to Monsieur de Voltaire, to Monsieur
de Fontenelle, and others, and I ask them if Boileau
and La Motte have not spoilt Homer's Ajax, and
Longinus vainly attempted to add to Homer's
beauties. I recognise the greatness of Longinus,
Boileau, and La Motte; but I am not attacking
them, only defending Homer.

This passage of Jupiter's oath and many others I

LETTER ON THE DEAF AND DUMB 203

could quote are sufficient evidence that it is useless
to try to add to Homer's beauties ; and Ajax' *
speech is proof positive that in trying to add
beauties to him there is a risk of destroying the
genuine beauties of the original. However talented
we are, we cannot write better than Homer, when
he is at his best. At any rate, let us understand
him before trying to outdo him. But he is so full
of that poetic symbolism I was just now speaking
of, that we cannot claim that we have completely
understood him when we have only read him ten
times. We might say that Boileau in literature has
suffered the same fate as Descartes in philosophy,
and it is through them we have learnt to correct
their minor errors.

If you ask me when this hieroglyphic use of
syllables was introduced into a language, whether it
is a peculiarity of a language in its early stage or
in the formative period, or of the perfected period,
I make answer that when men contrived their
primitive language they were apparently only
influenced by the facility or difficulty of pronounc-
ing certain syllables, and this facility (or difficulty)
was conditioned by the conformation of the organs
of speech. They did not seem to have considered
.what relation the elements of these words might
have from their quantity or sound to the physical
characteristics of the objects they stood for. The
vowel A, which is the easiest to pronounce, was first
used, and it was modified in various ways before
another sound was employed. The Hebrew Ian-

204 DIDEROTS PHILOSOPHICAL WORKS

guage supports this conjecture ; most of its words
are modifications of the vowel A, and this pecu-
liarity is in harmony with the traditions of this
people's antiquity. If we examine Hebrew closely,
we shall incline to consider it the language of the
primitive inhabitants of the earth. As for the
Greeks, they must have had the use of speech for a
long time and have thoroughly practised the subtilties
of pronunciation before they introduced quantity,
harmony, and syllabic imitation of noises and actions.
On the analogy of children, who, when they wish to
denote an object whose name is not known to them,
substitute for the name some of the object's sensible
peculiarities, 1 conjecture that it was during the tran-
sition from the primitive stage to the formative that
language became enriched with syllabic harmony,
and that rhythmic harmony was introduced into
writings as the language passed from the formative
to the perfected stage.

Whether these periods correspond to the actual
development of language or no, one who has no
feeling for the symbolic significance of words will
often only appreciate the definite significance of
epithets, and will be apt to call them superfluous ;
he will criticise ideas as loose, and images as far-
fetched, because he is blind to their subtle relation
to the subject ; he will not see that in Virgil's it
cruor the word it resembles in sound a gush of
blood and the falling of rain-drops on the leaves of
a flower, and so he will lose one of the trifles which
are all-important among the best writers.

LETTER ON THE DEAF AND DUMB 205

Reading the most lucid poets, therefore, is not
without its difficulties ; and I can assure you there
are a thousand men who can understand a geome-
trician for one who can understand a poet ; since
there are a thousand men who have common sense
for one man who has,. taste, and a thousand men of
taste for one whose taste is exquisite.

I am told that in the Abbe de Bernis' discourse
when Monsieur de Bissy was received into the
French Academy, Racine was blamed for want of
taste in the passage where he speaks of Hippolytus :

// suivait, fout pens if, le ckemin de Mycenes ;
Sa main sur les chevaux laissait flatter les renes ;
Ses superbes counters, qrfon voyait aufrefois
Pleins tfune ardeur si noble oblir a sa voix,
I? ail morne mainten<int et la t&te baissee,
Se jnb latent se conformcr a sa

If the Abbe is criticising the actual description, and
not its suitability in the context, it would be diffi-
cult to find a better and more modern instance of the
difficulty I just now spoke of, of reading poets.

There is nothing in these lines but speaks of
depression and sorrow :

// suivait, tout pensif) le chtmin de Mycenes ;
Sa main sur les chevaux laissait flatter les renes.

Les cJtevaux is better than ses chevaux ; and how well
the picture of what these superb horses once were

1 "All pensive, he followed the road to Mycenae; his hands loosed
the reins on his horses' necks ; and his superb horses, that used to obey
his voice with a noble fire, now with bent head and lack-lustre eye
seemed in sympathy with their master's sadness.'* Ptedre> Acte v,
Scene vl

2o6 DIDEROTS PHILOSOPHICAL WORKS

contrasts with their present condition I The nodding
of a horse's head, as it jogs wearily along, is imitated
in a certain syllabic nutation in the line itself :

E&il morne maintenant et la fete baisste.
But see how the poet brings all these details round
to his hero :

Ses superbes coursiers^ etc. . . .
Semblafent se conformtr a sa triste pcnste.

The word " seemed" seems too cautious for a poet,
for it is well known that animals attached to man
are affected by the signs of his joy or sorrow : the
elephant is affected by the death of his driver, the
dog mingles his voice with his master's, and the horse
is affected if his driver is sad. Racine's description
is therefore true to life : it is a noble description
and a poetic picture which a painter might reproduce
successfully. Poetry, painting, good taste, and truth
are all united for Racine and against the Abb6 de
Bernis' critique. 1

But if we were taught at Louis le Grand to notice
all the beauties of this passage of Racine's tragedy,
we were also told that they were out of place in the
mouth of Theram&ne, and that Th6se would have
had some excuse for stopping him and saying :
cc Enough of my son's chariot and horses; tell me

1 [In an addendum to this Letter Diderot apologises for his criticism of
the Abb de Bernis. He was at first told by a friend, who was present
at the meeting of the French Academy, that the Abb6 de Bernis had
criticised these lines of Racine's as both misplaced and bad in them-
selves. He was afterwards informed that the Abb merely criticised
them as misplaced ; and, far from claiming this criticism as original, he
quoted the lines as one of the most familiar instances of such mis-
placed eloquence.]

LETTER ON THE DEAF AND DUMB 207

about him. " It was not thus, the celebrated Poree
told us, that Antilochus announced the death of
Patroclos to Achilles. Antilochus approaches the
hero with tears in his eyes, and tells him the terrible
news in a few words : < Patroclos is no more. They
are fighting for his body. Hector has his armour."
There is more of the sublime in these two lines of
Homer than in all the pompous declamation of
Racine. c * Achilles, you have no longer a friend,
and your armour is lost." At these words we all
feel that Achilles must rush into the fray. When a
passage sins against truth and propriety, it is not
beautiful, either in tragedy or in epic. The details
in Racine's lines would only be suitable in the mouth
of a poet describing the death of one of his heroes.

So our learned professor of rhetoric taught us.
He possessed both taste and intelligence, and it
might be said of him that he was the "last of the
Greeks." But this Philopcemen fell into the same
mistake as people make to-day : he filled his works
too full of cleverness, and kept his taste for other
people's works.

To return to the Abb6 de Bernis. Did he only
wish to maintain that Racine's description was out
of place ? That is exactly what Father Poree taught
us thirty pr forty years ago. Or did he wish to hold
up the passage I have quoted as an example of bad
taste ? That is an original idea, but is it justified ?

I am told that there are many well-expressed and
well-reasoned passages in the Abb6 de Bernis' dis-
course : you are more likely to know this than I, as

208 DIDEROTS PHILOSOPHICAL WORKS

you always take the opportunity of hearing such
things. If it happens the Abbe de Bernis' discourse
does not contain the offending passage I have just
spoken of, and I have received an imperfect account
of it, that will make another instance of the utility
of a letter for the use of those who hear and
speak.

Wherever the language of signs is to be seen,
whether in a line of poetry or on an obelisk, whether
in a work of imagination or of mystery, it requires
a high degree of imagination and penetration to
understand it. But if it is so difficult to understand
poetry, why is it not more difficult to write poetry ?
I shall be told that c * everyone writes poetry," but
I shall reply, * * Hardly anyone writes poetry. "
Every imitative art has its own alphabet of signs,
and I much wish some man of taste and intelligence
would make a study of them and compare them.
The beauties of one poet have oftentimes been com-
pared with those of another. But one task is still un-
attempted to collect the beauties of poetry, paint-
ing and music, and show their analogies with one
another ; to explain how the poet, the painter anc
the musician will express the same idea; to seiz<
upon their most fleeting images of expression anc
examine the likeness, if there is a likeness, betweei
the imagery of the different arts. I should advis<
you to add this as a chapter to your Fine Art
reduced to a Single Principle, and I should also lik
you to include, at the beginning of your book,
chapter to define in what tfee beauty of nature coi

LETTER ON THE DEAF AND DUMB 209

sists. 1 For some people are of opinion that for lack
of one of these chapters your treatise is without a
firm foundation, and for lack of the other of little
practical use. Tell them, sir, the different methods
of the arts in treating the same subject, and
tell them it is false that nature is only ugly when
out of place. They ask me why an old gnarled and
twisted oak, with its branches lopped, and which I
should have felled if it grew near my door, is just
the tree a painter would set by my cottage door, if
he had to paint it ? Is the oak beautiful or ugly ?
Which is right the owner or the painter ? There is
no subject of imitative art which does not arouse
this and other difficulties. They also want to know
why a scene which is admirable in a poem is not at
all suitable for a painting? In those fine lines of
Virgil :

Interea magno misceri mitrmure pontitm
Emissamque hiemem sensit Neptunus^ et imis
Stagna refusa vadis ; graviter commotus et alto
Prospidens, summa pladdum caput exiulit unda;*

they ask why it is the painter cannot seize the
striking moment when Neptune raises his head

1 Diderot used to call Batteux* book a headless book, because after
he had reduced all the fine arts to a single principle that of imitating
the beauty of nature, he never explained what the beauty of nature
consisted in. Naigeon, Memoires*

2 Meantime the turmoil of the main
The Tempest loosened from its chain ;
The waters of the nether deep
Upstarting from their tranquil sleep
On Neptune broke : disturbed he hears,
And, quickened by a monarch's fears,
His calm broad brow o'er ocean rears.

d^ lib. i, v. 128 (frs. Conington).

14

2fo DIDEROTS PHILOSOPHICAL WORKS

above the waves ? Why should the god, who then
looks like a decapitated man, cut such a poor figure
on the water, when the effect in the poem was so
impressive? Why is it that what appeals to our
imagination in poetry will not please our eyes when
painted ? Perhaps there is one beauty of nature for
the painter and another for the poet ? Heaven knows
what conclusions they will draw from this theory.
I hope you will deliver me from these busy bodies ;
meantime, I am going to give you a single example
of the imitation of one subject in nature by poetry,
painting and music*

The subject is a dying woman. The poet will say :

#, graves oculos conata adtollere, rursus
Deficit* Infixum stridit sub pectore vulnus
Ter sese adtollens cubitoque adnixa levamt ;
Ter revoluta toro est oculisque errantibus alto
Qu&sivit c&lo lucem, ingemuitque referta ; 1
or

Vita quoque omnis
Omnibus e nervis atque ossibus exsofoatur?

The musician will begin by descending a semitone
(a) : Ilia, graves oculos conata adtollere^ rursus deficit ;
then he will go up a fifth, and after a rest, by the
still more difficult interval of a tritone (ft).

1 The dull eyes ope, as drowned by sleep,

Then close ; the death wound gurgles deep
Thrice on her arm she raised her head,
Thrice sank exhausted on "the bed.
Stared with blank gaze aloft, around
For light, and groaned as light she found.

Virgil, Mneid, lib. iv, v. 688 (trs. Conington).

2 ' And life break wholly up out of all the sinews and bones.

Lucretius, de Rerum Nat** lib. i, w. 810, Su.

LETTER ON THE DEAF AND DUMB 211

Ter sese adtollens will go up a semitone (c) :
Oculis errantibus alto quasivit ccelo lucem. This little
interval will express the ray of light This is the

iLxemple

=J=t

me -nuzinrs & m&ryeiix if

^f

tjf.

\j 7 ^ ;

f e.

FIG. 8.

dying woman's last effort. After this she will sink
by scale (d) : Revoluta tore est. She will expire at
last, and breathe her last by an interval of a semitone
(e) : Vita quoque omnis omnibus e nervis atquc ossibus

2i2 DJDEROTS PHILOSOPHICAL WORKS

exsolvatur. Lucretius expresses the dying away of
her strength by the weight of the two spondees
exsolvatur ; and the musician will express it by two
minims, tied (/) : and the cadence on the second of
the minims will give a very striking imitation of the
vacillating motion of a dying lamp.

Now look at the painter's method of expression,
and you will recognise the exsolvatur of Lucretius
in the legs, the right arm, and the left hand. The
painter who can express but a moment in time has
not been able to represent so many symptoms of
dissolution as the poet, but they are much more
affecting; the painter shows *us reality, whereas the
expressions of the poet and the musician are but
symbols. When the musician is an artist, the ac-
companiment either emphasises and strengthens the
melody, or brings in new ideas which the subject
demands and which the melody cannot express.
Thus the first bars of the bass express a gloomy
harmony, made up by a superfluous chord of the
seventh, placed as it were outside the ordinary rules
and followed by another chord, discordant in sound
and of a diminished fifth (g\ The rest will consist
of a series of minor sixths and thirds (A), which are
descriptive of exhaustion of strength and prepare
the mind for its total extinction.

It Is the equivalent of Virgil's spondees :

Alto qu&sivit c<xlo lucem.

This is but the rough sketch, which I leave for a
more accomplished hand to complete. 1 make no

LETTER ON THE DEAF AND DUMB 213

doubt that, in this very subject I selected, instances
could be found in our painters, poets, and musicians
which would offer more and more striking analogies
between the different arts. But I leave it to you,
sir, to look for them and utilise them, for you must
be painter and poet, philosopher and musician ; for
you would not have attempted to reduce the fine
arts to a single principle, if you had not been equally
well acquainted with them all.

The poet and the orator gain by studying harmony
of style, and the musician finds his compositions
are improved by avoiding certain chords and certain
intervals, and I praise their efforts ; but at the same
time I blame that affected refinement which banishes
from our language a number of vigorous expressions.
The Greeks and Romans were strangers to this false
refinement, and said what they liked in their own
language, and said it as they liked. By over-
refining we have impoverished our language ; and
though there may be only one term which expresses
an idea, we prefer rather to weaken the idea than
to express it by some vulgar word or expression.
How many words are thus lost to our great. imagina-
tive writers, words which we find with pleasure in
the pages of Amyot and Montaigne ! They were
at first rejected from a refined style, because they
were commonly used by the people ; later on they
were rejected by the common people, who always ape
their betters, and they are become entirely obsolete.
I believe we shall soon become like the Chinese,
and have a different written and spoken language.

314 DIDEROTS PHILOSOPHICAL WORKS

This, sir, is almost my last observation ; we
journeyed on together, and I feel it is time to quit
one another. If I detain you for a moment longer
as we are leaving this maze in which I have led
you, it is but to recapitulate in a few words its
turnings and windings.

/ believed that, in order to clearly understand the
nature of inversions, we should examine the forma-
tion of spoken language.

/ inferred from this examination (i) that our
language was full of inversions when compared with
the animal language, or with the first stage of spoken
language, when it existed without cases, declensions,
conjugations, and syntax ; (2) that if we have in
French hardly any of what we call inversion in
ancient languages, this is perhaps due to modern
peripateticism, which by realising abstractions gave
them the place of honour in speech.

As a consequence of these truths I thought that
we could, without studying the origin of spoken
language, obtain results by the study of gesture-
language alone.

/ suggested two methods of learning the language
of gesture experiments with a " theoretical mute,"
or long conversations with one born deaf and dumb.
The idea of a theoretical mute, or taking (hypotheti-
cally) speech from a man, to get a clearer idea of the
formation of language, has led me to consider man
as divided into as many distinct and separate entities
as he has senses ; and I think that if, to form a
correct judgment of an actor's intonation, we must

LETTER ON THE DEAF AND DUMB 215

listen to him without seeing him, it is natural that
we should look at him without listening to him if
' we are to form a correct opinion of his gestures.

In reference to energetic gesture-language ', I related
some striking examples of this, which led me to dis-
cuss a variety of the sublime which I call sublimity
of situation.

The order that existed in the gestures of one born
deaf and dumb (whose informal conversation seemed
to me more valuable than experimenting with a
( ' theoretical mute "), and the difficulty in transmit-
ting certain ideas to this deaf-mute, led me to dis-
tinguish in spoken language between those symbols
which were first introduced and those of later
introduction.

/ saw that the symbols which in speech denoted
indefinite divisions of quantity and time were among
the last to be introduced, and I realised why some
languages were without several tenses, and why
other languages used one tense with two meanings.
This lack of tenses in one language, and this mis-
use of tenses in another, led me to distinguish three
stages in the formation of a language its primitive \
its formative, and its perfected state.

/ saw, when language was formed, that men's
minds were hampered by syntax, and by the im-
possibility of thinking in the order which reigns in
Greek and Latin periods. Hence I concluded (i) that,
whatever the order of words in an ancient or modern
language, the writer's mind followed the order of
French syntax ; (2) that, as this syntax is the

216 DIDEROT S PHILOSOPHICAL WORKS

simplest of all, the French language had the advan-
tage in this and many other respects of the ancient
languages.

Moreover, / proved by the introduction and the
utility of the article hie and tile in Latin and le in
French, and by the fact that we have to experience
several perceptions simultaneously in order to form
a judgment or make a speech, that when the mind is
not hampered by Greek and Latin syntax the order
of its ideas is not dissimilar to our syntax.

In tracing the transition of language from the
formative to the perfected state we meet with
harmony of style.

f compared harmony of style with musical harmony,
and / am convinced (i) that the first harmony in
words was the result of quantity and a certain com-
bination of vowels and consonants, suggested by
instinct ; and that in sentences it was the result of
the order of words ; (2) that this periodic and syllabic
harmony produced a sort of language of symbols
which is peculiar to poetry ; and I then treated this
symbolic language, and analysed several passages of
the greatest poets.

As a result of this analysis I ventured to maintain
that it is impossible to translate a poet into another
language, and that it is an easier thing to understand
a geometrician than a poet.

I proved by two examples the difficulty of clearly
understanding a poet : by the example of Longinus,
Boileau, and La Motte, who misunderstood a passage
in Homer; and by the example of the Abb de

LETTER ON THE DEAF AND DUMB 217

Bernis, who seemed to me to misunderstand a passage
of Racine.

After I had defined the date when syllabic
symbolism was introduced into a language, /
observed that every imitative art had its own
language of signs, and that it would be a good
thing if a man of taste and learning would under-
take to compare them.

Here I have hinted that this work is expected of
you ; and that those of us who have read your Fine
Arts reduced to the Imitation of Beauty in Nature
demand that you should define in what beauty in
nature consists.

I expect you to compare the language of signs
in poetry, painting, and music ; meantime, I have
ventured to make some observations of my own upon
this subject.

Musical harmony ', which was necessarily included
in the discussion, led my thought to the harmony of
speech. I said that the limitations imposed by each
were much more supportable than an affected refine-
ment which tends daily to impoverish our language ;
and I emphasised this point until I came to that
passage where I took leave of you.

But do not suppose, from my last observation,
that I withdraw my preference for French above
all the languages of antiquity and the majority of
modern languages. This is still my feeling, and I
still think that French is superior in utility (if not in
beauty) to Greek, Latin, Italian and English.

The objection may be perhaps raised that if, as I

2iS DIDEROTS PHILOSOPHICAL WORKS

submit, the languages of antiquity and those of our
neighbours are superior in beauty, we all know that
these languages do not play us false when we wish
to treat of ordinary practical matters.

But I make answer that if our language is admir-
able for its utility, it can also lend itself to the pur-
poses of art. There is no role it has not successfully
assumed. It has been gay and fanciful with Rabelais,
narve with La Fontaine and Brantdme, musical in
Malherbe and Flechier, sublime in Corneille and
Bossuet. What an instrument it is in Boileau, in
Racine, in Voltaire, and in a host of other writers of
poetry and prose ! Do not let us waste our pity on
it. If we know how to use it, our works will be as
precious in the eyes of posterity as the works of
classical antiquity are in our own. In the hands of
a commonplace man, Greek, Latin, English and
Italian will utter only commonplaces, while the pen
of a man of genius will work miracles with French.
Whatever language it is written in, a work inspired
and sustained by genius never falls or flags.

NOTES

{Note I. The specimens of the arithmetic which
I have perused and reduced to common numbers
are certain arithmetical tables, which he had
computed and preserved for his own use ; but for
what purposes they seem calculated does not easily
appear. They seem to have some relation to the
tables of natural sines, tangents, and secants ; but
their full use I must leave to future inquiry. They
are four pieces of solid wood, of the form of
rectangular parallelepipeds, each about eleven
inches long, five and a half broad, and something
about half an inch thick. The two opposite faces
of every one were divided into little squares after
the manner of the abacus above described, but they
were perforated only in the necessary places where
the pins were stuck fast up to the head. Each face
exhibited nine small arithmetical tables of ten
numbers each ; and every number, generally speaking,
consisted of five places or figures. " Dr Saunderson's
Palpable Arithmetic decyphered," prefixed to Saun-
derson's Algebra (1740), pp. xxiii and xxiv.]

{Note 2. A blind man moving in the sphere of
a mathematician seems a phenomenon difficult to

be accounted for : Tully mentions it as a thing

219

220 DIDEROTS PHILOSOPHICAL WORKS

scarce credible in his own master in philosophy,
Diodorus, " that he exercised himself in philosophy
with more assiduity after he became blind ; and,
what he thought next to impossible to be done
without sight, that he professed geometry, describ-
ing his diagrams so expressly that his scholars drew
every line in its proper directions. "

St Jerome relates a more remarkable circum-
stance in Didymus of Alexandria, who, ' though
blind from his infancy, and therefore ignorant of the
very letters, not only learnt logic, but geometry
also to perfection, which seems the most of any-
thing to require the help of sight. "

Trithemius, de Scriptoribus Eccles.^ mentions
Nicaise de Voerde, at Mechlin, " who, though blind
from the first year of his age, became so eminent
in learning, that he taught the canon and civil law
in the university of Cologne, and quoted books
only from having heard them read to him. " I have
further heard of a Hollander, and some others,
whom blindness did not hinder from excelling in
mathematical learning. Indeed, if we consider that
the ideas of extended quantity, which are the chief
objects of mathematics, may as well be acquired from
the senses of feeling as that of sight ; that a firm
and steady attention is the principal qualification for
this study ; and that the blind are necessarily
more abstracted than others, we shall perhaps
find reason to think there is no other branch of

science more adapted to their circumstances. Life

of Saunderson^ ibid.}

NOTES 221

[Note 3. The elephant and tortoise illustration
had been first introduced by Locke In his criti-
cism of the idea of substance (Essay concerning
Human Understanding, bk. ii, ch. 13, 19, and
again ch. 23, 2). It had been further developed
by his disciple Shaft esbury (Characteristics: the
Moralists ', vol. ii, p. 15) to criticise the solutions
given to the problem of the origin of evil. From
Shaftesbury Diderot appears to have taken both the
idea and the illustration : in paragraph xxii of his
Sufficiency of Natural Religion, where he boldly
applies to the story of Adam the ridicule which
Shaftesbury seemed to cast on the myth of
Prometheus only. Why does man suffer in this
world? That is a mystery, says the Christian.
That is a mystery, says the man of science.
Observe that the Christian's answer is finally re-
duced to this. If he says : ' ' Man suffers, because
his forefathers sinned," and you press him with
c Why should the descendant pay for his forefather's
folly ? " he replies : " That is a mystery." * ' Well,"
I should reply to the Christian, "why did you not
say at first, as I do, that if man suffers in this
world, apparently without deserving it, that is a
mystery ? Don't you see that your explanation is
like the Chinese explanation of the suspension of the
earth in mid air? ' Chinaman, what carries the earth?'
A great elephant. ' And what carries the elephant ?'
*A tortoise.' 'And what carries the tortoise?'
' I don't know.' " Ah, my friend, drop the elephant
and the tortoise and admit your ignorance.

222 DIDEROT S PHILOSOPHICAL WORKS

In the above instance Diderot had described the
elephant and tortoise theory to a " Chinois " ; in the
Letter on the Blind he reverted to the original
" Indian."]

\Note 4. We are ... to consider concerning
perception, that the ideas we receive by sensation
are often in grown people altered by the judgment,
without our taking notice of it. When we set
before our eyes a round globe, or any uniform
colour e.g. gold, alabaster, or jet, 'tis certain that
the idea thereby imprinted in our mind is of a flat
circle variously shadowed, with several degrees of
light and brightness coming to our eyes. But we
have by use been accustomed to perceive what kind
of appearance convex bodies are wont to make on
us ; what alterations are made in the reflections
of light, by the difference of the sensible figures
of bodies ; the judgment presently, by an habitual
custom, alters the appearances into their causes, so
that from that, which truly is variety of shadow or
colour, collecting the figure, it makes it pass for a
mark of figure, and frames to itself the perception
of a convex figure, and an uniform colour ; when the
idea we receive from thence is only a plane variously
coloured ; as is evident in painting. To which
purpose I shall here insert a problem of that very
ingenious and studious promoter of real knowledge,
the learned and worthy Mr Molineux, which he was
pleased to send me in a letter some months since, and
it is this :

NOTES 223

11 Suppose a man born blind, and now adult ', and
taught by his touch to distinguish between a cube
and a sphere of the same metal and nighly of the
same bigness -, so as to tell, when he felt one and
f other, which is the cube, which is the sphere.
Suppose then the cube and sphere placed on a table,
and the blind man to be made to see : Queer e, whether
by his sight before he touched them, he could now
distinguish, and tell, which is the globe, which is tJie
cube. To which the acute and judicious proposer
answers, Not. For though he has obtai?ied the ex-
perience of how a globe, how a cube affects his touch,
yet he has not yet attained tJie experience, that what
affects his touch so or so, must affect his sight so or
so. Or that a protuberant angle in the cube, that
pressed his hand u?iequally, shall appear to Ms eye
as it does in the cube. I agree with the thinking
gentleman whom I am proud to call my friend, in
his answer to this his problem ; and am of opinion,
that the blind man, at first sight, would not be able
with certainty to say, which was the globe, which
was the cube, whilst he only saw them ; though he
could unerringly name them by his touch, and
certainly distinguish them by the difference of their
figures felt." An Essay concerning Human Under-
standing, vol. i, pp. 107, 108 (ed. 1721).]

\Note 5. Condillac, Etienne Bonnot de (1715-
1780), a French philosopher, was born at Grenoble,
and took orders and became the Abb6 de Mureau.
The profession was nominal, and Condillac's whole

224.

DIDEROT S PHILOSOPHICAL WORKS

life was devoted to speculation. His works are : an
Essay on the Origin of Human Knowledge (1746),
the Treatise on Systems (1798), Treatise on Sensa-
tions (1767-1773), in fifteen volumes, and two post-
humous works Logic (1781), and the Language of
Calculation (1798). In his earlier days in Paris he
came much into contact with the circle of Diderot.
He spent his later years in retirement at a property
he had bought near Beaugency, and died there on
August 3rd, 1780. Condillac is important as a
psychologist, and as having established systematic-
ally in France the principles of Locke, whom Vol-
taire had lately made fashionable. In his Treatise
on Sensations he questions Locke's doctrine that the
senses give us an intuitive knowledge of objects,
and that the eye judges naturally of shapes, sizes,
positions, and distances.

The plan of Condillac's book is the idea of a
statue organised like a man, with a soul which has
never received an idea, into which no sense-impres-
sion has ever penetrated. He then treats of the
senses one by one, beginning with smell As an
example of his careful and detailed treatment, the
headings of some of the chapters may be quoted :
" Of the Ideas of a Man limited to the Sense of
Smell " ; "Of a Man limited to the Sense of Hearing";
"Of Smell and Hearing Combined"; " Of Taste
by Itself, and of Taste Combined with Smell and
Hearing " ; " Of a Man limited to the Sense of Sight. "
In the second section of the treatise the statue is
invested with the sense of touch which first informs

NOTES 225

him of the existence of external objects. ''Apart
from any definite propositions, Condillac did a
notable work in the direction of making psychology
a science : it is a great step from the desultory,
general observation of Locke to the rigorous analysis
of Condillac, short-sighted and defective as that
analysis may seem to us in the light of fuller
knowledge. " x ]

\Note6. William Cheselden (1688-1752), a well-
known surgeon and anatomist. In 1728 he wrote
a paper (Phil. Trans ., xxxv, 447) entitled "An
account of some observations made by a young
gentleman who was born blind . . . and was couch'd
between thirteen and fourteen years of age." The
account of this youth's experience is clear and
masterly, but brief, and most students have regretted
that the opportunity was not 'seized for more detailed
observations. See also Voltaire, Elemens de la
philosophic de Newton, pt ii, ch. vii (CEuvres com-
pletes, ed. Beuchot, t. i, 1879, pp. 4&9> 47), where
Voltaire summarises the case.]

1 Art. " Condillac," Encyclopedia Briiannica, vol. vi, pp. 849-851
(nth edition).

APPENDIX
BLINDNESS

FROM the Encyclop&dia of Diderot and d'Alembert,
vol. i, p. 870. The translation is that which appeared
in Select Essays from the Encyclopedy, pp. 132-147,
London (1782), in which it is attributed to d'Alem-
bert. The translation has been revised and corrected.
In the translation, two passages which were omitted
have been inserted, i.e. the sentence, " If we except
certain passages which are not immediately connected
with the subject and may offend pious ears/' and the
paragraphs, "Imagine a square "to ''Philosophers
and beginners would have found it useful."

BLINDNESS

ONE may be born blind, or become so through acci-
dent or malady. It is not our intention here to
treat either of the diseases of the eye, or of other
accidents that may occasion a loss of sight. We
shall confine ourselves to make philosophical reflexions
upon blindness, through the ideas of which we are

326

APPENDIX 227

deprived by it as well as through the advantage
acquired by the other senses in consequence of it.

From the known truth of the sense of seeing being
more fitted to distract us by the diversified qualities
of objects which it presents to us at once, it follows
that they who are deprived of this faculty must
naturally, for the most part, apply with a closer
attention to the objects which fall under their other
senses. And this is the principal reason of that
delicacy of touch and hearing that has been observed
in some blind people, which is by no means the effect
of a real superiority in these two senses ; whereby
nature means, as it were, to compensate in some
sort for their loss of sight.

So true is this position, that a person become blind
through accident finds often in the succour of the
other senses a resource which he knew not of before ;
and this is to be ascribed solely to that person's being
less distracted and become more capable of attention.
But it is chiefly in persons born blind that we are to
remark (if such an expression may be allowed) the
miracles of blindness.

An anonymous author published in the year 1749
a little philosophical work, very elegantly written,
and entitled, Letter on Blindness for the use of those
who can see ; with this motto :

" Possunt quia posse videntur,"

which alludes to the prodigies that have been observed
in folks born blind. We purpose to give in this
article an extract of that ingenious work, whose

228 DIDEROTS PHILOSOPHICAL WORKS

metaphysical reasoning, though very subtle, is yet
true in general, if we except certain passages which
are not immediately connected with the subject and
which may be offensive to pious ears. 1

The author sets out by making mention of a
person born blind with whom he was acquainted,
and who is probably still alive. This extraordinary
man, who lived at Puisaux in Gatinais, was both
chemist and musician. He taught his son to read
with characters in relievo. He could judge with
exactness of symmetry. But it is very likely that
the idea of symmetry, which is with us in many
respects but a matter of mere convention or agree-
ment, is still more so to him* The definition which
he gives of a looking-glass has something very
singular. "It is," according to him, "a machine,
by means whereof things are exhibited in relievo
out of themselves." This definition indeed may
appear absurd to a blockhead who has eyes ; but
a true philosopher, however keen-sighted, will pro-
nounce it to be no less subtle than surprising. " Had
Descartes been born blind," says our author, "he
might be proud of it." By what a delicate train of
ideas must he have been led so far ! Our blind man
could have, in this affair, no knowledge but through
the medium of his feeling. He conceived, from
what he had heard other men relate to him, that
it is by the faculty of sight they come to a know-
ledge of objects, as in a kindred manner he does by
the mediation of feeling : it was the only notion he

1 " If we except . . . ears '* omitted in the original translation.

APPENDIX 229

could form to himself. He had learned, moreover,
that a man cannot see his face, though he can touch
it. Sight then, in his sense, must have been a
species of feeling or touching, that extends itself
to any proper objects that are different from our
countenance and placed at a distance from it. Be-
sides, the sense of touching or feeling in this case
excited in him the idea of a relievo. Therefore,
adds he, "a looking-glass is a machine that places
us in relievo out of ourselves. " Let it be observed,
that the words in relievo are by no means redundant
here; for, had the blind man simply said, "which
places us out of ourselves," it would have been an
absurdity ; because how can we conceive an object
that is to 'double itself? The words in relievo here
are only applied to the surface ; wherefore by " our-
selves being placed in relievo out of ourselves,"
nothing more is meant than the representation of
the surface of our bodies being made out of our-
selves.

The blind man must have been induced by his
manner of reasoning to think that feeling represents
to him only the surface of bodies, and that therefore
the species of touching or feeling called sight gives
us but an idea of the relievo, or the surface of bodies,
without giving that of their solidity ; the words in
relievo here meaning no more than surface.

I own here that the blind man's attempt at an
explanation, notwithstanding this restriction, is an
enigma to him ; but a pleasure that must hence
result to all reflecting minds is to observe (consider-

230 DIDEROTS PHILOSOPHICAL WORKS

ing his situation) the very ingenious method employed
by him to diminish, and, as far as by him practicable,
to solve the enigma.

It must strike everybody that mirrors, and every
kind of glasses which enlarge, diminish, or multiply
objects, were impenetrable mysteries to him. c c He
asked if the glass that increased objects was
shorter than that which lessened them ; or if that
which drew them near was less than that which
threw them off at a distance ; and not being able to
conceive how the other ourselves were impalpable to
feeling, he cried out, " I perceive that two senses are
put in contradiction to one another by the means of
a little machine ; another, more perfect, would make
them agree ; and a third, still more perfect and less
perfidious, would make all those phantoms disappear
and convince us that we had been in error." What
philosophical conclusions might not a person born
blind be enabled to bring against the fallacy of our
senses !

He defines the eyes to be an organ on which the
air causes the same effect as a stick upon the hand.
The author we abstract from here observes that this
definition has some resemblance with that of
Descartes, who in his Dioptrics compares the eye
to a blind man that touches objects at a distance
with his stick. The rays of light are the sticks of
the clear-sighted.

Our blind man's memory of sounds is to a most
amazing degree ; and he distinguishes among the
variety of voices with as much accuracy and quick-

APPENDIX 23!

ness as those who see can among that of faces.
The succour which he derives from his other senses,
and the very surprising use which he makes thereof,
to the astonishment of all whom he has any concern
with, render him almost indifferent about the loss of
sight. He is sensible enough that in some circum-
stances he has advantages over those who can see ;
which make him, instead of being desirous of sight,
to wish, as an equivalent thereto, for longer arms.

He addresses himself directly towards the place
whence any noise or voice affects his ear. He
judges of the proximity of fire by the degree of heat ;
of the plenitude of vessels by the noise which
liquors make as they are poured from them ; of the
nearness of bodies by the action of the air upon his
face : he can distinguish an open street from a cul-
de-sac (one that has no passage through it) ; which
proves that the air, relatively to him, is never in an
absolute state of rest, and that his countenance is
instinctively sensible of the least vicissitude in the
atmosphere.

He judges wonderfully well of the weight of
bodies and the capacity of vessels ; he has trained
his arms to serve him as exact scales or balances,
and his fingers as compasses that never deceive him.
The smoothness of bodies has as many variations for
him as the sounds of the voice. He judges of beauty
by the touch ; and, what is singular, he makes the
sound of the person's voice, with their manner of
pronouncing, come in for a share of this judgment.

He executes several little works in the turning

232 DIDEROTS PHILOSOPHICAL WORKS

way and with a needle ; he takes a level with a
square ; he puts together or takes asunder pieces of
common machinery ; he performs pieces of music,
the notes and their value being first told him ; he
estimates, with much more precision than we do,
the progress of time, and that by the succession of
actions and thoughts.

He has an implacable hatred of thieves ; and the
reason, no doubt, arises from the difficulty, or rather
impossibility, in which he is to perceive when he
is robbed ; he has but little, or rather scarce any,
notion of what modesty consists in ; he looks upon
clothes as necessary for protecting our bodies from
the injuries of the air, but he cannot comprehend
why certain parts of the body should be covered
preferably to others. " Wherefore," says the author
we abridge from, " Diogenes would not have ranked
as a philosopher in the opinion of our blind hero."
In fine, the exterior appearance of worldly pomp,
with which the generality of mankind are so much
affected, impose not upon him in the least, which
in the kingdom of reason is no despicable article."

We pass over in silence a great number of very
subtle and refined reflections made by the author we
quote from upon the French blind man, to proceed
to what he says of another celebrated personage in
the same situation ; and that is the famous Saunderson
of England, a professor of mathematics at CambridgCj
who died a few years ago.

When an infant, he lost his sight by the small-pox,
and so early that he did not remember to have ever

APPENDIX

233

seen. He had no more ideas of light than a person
born blind. Notwithstanding his misfortune, he
made such a surprising progress in the mathematics
that the professorship thereof was conferred on him by
the above-mentioned University. His lectures were
exceedingly clear ; and the reason assigned for it is,
that he used to address himself to his pupils as if
they were all deprived of sight : whence it followed,
of course, that the blind teacher who could explain
his meaning clearly to blind pupils must have a
great advantage with those who could see, from
their quickness of conceiving him. He taught his
scholars the calculations he had made.

Imagine a wooden square divided by perpendicular
lines into four small squares ; suppose this square
pierced with nine holes capable of receiving pins of
the same length and thickness, but of which some
had larger heads than others.

Saunderson had a great number of these little
squares traced on a large board. To denote the
cipher nought, he would place a large-headed pin in
the centre of one of these squares, and no pin in the
other holes. To denote the number i, he placed a
small-headed pin in the centre of a little square.
To denote the number 2, he placed a large-headed
pin in the centre, and above, in the same line, a
small pin in the corresponding hole. To denote 3,
a large-headed pin in the centre, a small-headed pin
in the centre, and a small-headed pin in a hole
above to the right ; and so on. Thus Saunderson,
when touching a small square, perceived at once the

234 DIDEROT'S PHILOSOPHICAL WORKS

number 'it denoted, and on glancing at the following
table we shall see his method of addition by means
of these small squares :

12345

23456

34567

45678

56789
67890
78901
89012
90123

Running his fingers down each vertical row of
figures from top to bottom, he added up in the
ordinary manner, and marked the sum by means of
pins placed in squares at the foot of the above
numbers. The same board divided into squares
served for geometrical demonstrations. He placed
large-headed pins in the holes in the direction of a
straight line, thus forming polygons, etc.

Saunderson also left some instruments which were
of use to him in his study of geometry, but how he
used them is not known.

He published his Elements of Algebra, equal to
the best that has been published on this subject,
but, as our author observes, elements of his geometry
would have been even more interesting. I have
heard from a person of his acquaintance that the
demonstrations of the properties of solid bodies,

APPENDIX 235

which are usually a matter of considerable difficulty,
were child's play to him. His mind moved in a
pyramid, an icosahedron, from one angle to another,
with the greatest ease ; he imagined planes and sec-
tions in these solids without any effort. Perhaps for
this reason the demonstrations which he might have
given would have proved more difficult than those of
a clear-sighted geometrician ; but his demonstra-
tions on plane geometry would in all probability be
extremely clear, and perhaps singular. Philosophers
and beginners would have profited by them.

Although it may appear very singular to the many
that he gave lectures upon optics, yet to philo-
sophical minds the miraculous of this affair dis-
appears, on reflecting that a blind man, without any
idea of light or colours, may give lectures upon
optics, in proceeding like the geometricians who
look upon the rays of light as straight lines that
ought to be disposed of and arranged according
to certain laws in order to cause the phenomenon
of vision, as well as those observable in mirrors,
optic glasses, etc.

Saunderson in running his hand over a series of
medals could distinguish the false from the true,
even when they were so well counterfeited as even
to deceive the practised eye of a connoisseur ; he
could judge of the exactness of mathematical instru-
ments by running his fingers over the divisions. He
was, like the before-mentioned blind man, sensible
of the least vicissitudes in the atmosphere ; and he
perceived (in calm weather especially) the presence

236 DIDEROTS PHILOSOPHICAL WORKS

of objects near him. As he sat one day in his
garden meditating on astronomical observations, he
distinguished, by the impression of the air on his
countenance, the different times when the sun was
covered with clouds and when it was not ; which
is so much the more extraordinary, as that he was
deprived not only of sight but of the organ.

The pretended history of Saunderson's last mo-
ments, printed in England, is an absolute imposi-
tion ; which, though held by many learned men to
be highly criminal against the majesty of science,
might be deemed only a stroke of mere pleasantry
were it not occasioned by so solemn and respectable
a subject.

Our author afterwards treats in a cursory manner
of several other blind personages who in spite of the
loss of one sense have made a wonderful progress
in the arts and sciences. He farther observes, and
not improbably, that the famous Tiresias, who is
said to have become blind because he had penetrated
into the secrets of the gods and could predict future
events, was in all likelihood some celebrated blind
philosopher, whose name fabulous history hath
transmitted down to us. Perhaps he was the most
renowned philosopher of his time, because he could
foretell eclipses (which to an ignorant people must
appear astonishing). His becoming blind towards the
latter end of his life was doubtless occasioned by too
continued an application that over-fatigued his eyes in
making such a variety of nice observations, as hath
since indeed been the case with Galileo and Cassini.

APPENDIX 237

There have been many instances of people born
blind being restored to sight ; as, for example, that
young lad, about thirteen years old, whom Mr
Cheselden, a celebrated surgeon at London, re-
lieved from the cataract that had rendered him
blind from his birth. This great operator curiously
observed the progressive manner of his beginning
to see, which he published in No. 42 of the Philo-
sophical Transactions, and in the fifty-fifth number of
the Toiler, with his remarks thereon. Here follows
an extract of those remarks* from the third volume
of Natural History, by Messieurs de Buffon and
d'Aubenton :

" This youth, notwithstanding his blindness, could
distinguish the day from the night, as can all those
who are blinded by cataract. He could distinguish
any strong light, as he could also the colours black,
white, and scarlet ; but he could not discern the form
of bodies. The operation was first made upon one
eye. As soon as the young patient began to see, all
the objects before him seemed to him as if they were
applied to his eyes ; and those that appeared the
more pleasing to him, although he could give no
reason for it, were such as had a regular form. He
did not, however, know the colours, which, while
blind, he could distinguish by the aid of a strong
light. He could not discriminate one object from
another, however different the forms were. When
the objects, which he had known before by feeling,
were presented to him, he considered attentively
in order to recognise them ; but, all of a sudden, a

238 DIDEROTS PHILOSOPHICAL WORKS

general act of oblivion followed from the multi-
tude of things that crowded in upon him for
admiration.

'* He was much surprised in not finding those
persons handsomer whom he had loved more than
others. He was a long time before he could be
made to comprehend how pictures represented solid
bodies. He at first looked upon them as planes
differently coloured ; but when he was undeceived,
and on applying his hands to them, discovered
nothing beside surface, he asked whether it was the
sight or the touch which had deceived him. He
expressed great surprise that in a little space the
picture of an object much larger than the space could
be contained ; as, for example, the human counten-
ance in a miniature portrait, which appeared to
him equally impossible as to make a quart contain
a bushel.

"At first he could bear but a very small quantity
of light, and saw all objects very large ; but by
degrees the first seen looked smaller, as he accus-
tomed himself to see larger. Although he very
well knew the chamber in which he was to be of
less dimensions than the house, yet he could not
conceive why the house should appear larger than
the chamber.

* * Before the restitution of his sight, he was but
very little anxious about the recovery of this addi-
tional sense to him, because he knew not the loss of it,
and was conscious of himself that in some articles he
enjoyed peculiar advantages unknown to others who

APPENDIX 239

could see. But as soon as he came to view objects
distinctly, then he felt real transports of joy.

' ' About a year after the first operation, the second
was performed upon the other eye, and was crowned
with equal success. He saw at first, with this
second eye, the objects much larger than they
appeared to the other ; but, however, not so large
as they had appeared at first to it, after the opera-
tion a year before. When he looked steadfastly on
an object with both his eyes, he said that the object
appeared to him as big again as when he looked at
it only with his first eye."

Mr Cheselden mentions several others born blind,
whom he had freed from the cataract, and observed
in them the same phenomena, without entering into a
like detail He remarks that from their not having
been used to move their eyes during the state of blind-
ness, it was but by degrees that they learned how
to direct them towards objects.

From the result of these experiments it must
clearly appear that the sense of seeing arrives at
perfection but by slow degrees, and is at first very
confused ; and that we learn to see, pretty nearly
as we learn to speak. A new-born babe, that opens
its eyes for the first time to the light, feels, no
doubt, the same progressive emotions which have
been observed in the lad born blind. By the agency
of feeling and custom the erroneous judgments of
infant sight are corrected gradually.

Let us now return to our author, who says : " We
seek for people born blind, in order to examine

2A&DIDEROTS PHILOSOPHICAL WORKS

was discovered. I made use of it, and explained to
the dumb man that he was mistaken, and that I had
escaped though he did not expect me to. But he,
by pointing his finger at the spectators one after
another, and making a motion of the lips, accom-
panied by a sweeping movement of his arms in the
direction of the door and the tables, replied that it
was no credit to me to have got out of my difficulty
by calling in all and sundry to my help. His
gestures were so significant that no one could mis-
understand him, and the popular expression "all
and sundry " * occurred to many at the same time :
this expression was definitely translated by our
dumb man's gestures.

You know, at least you have heard, of a singular
machine with which the inventor proposed to give
sonatas in colour. I thought that if anyone could
appreciate a performance of ocular music, and could
judge of it without prejudice, it would be a man
born deaf and dumb. I therefore took my friend
to the house in the rue St Jacques, where the
operator and the machine with colours was exhibited.
Ah, sir, you would never guess the kind of impression
that it made on him, nor the ideas it suggested.

You see that it was impossible to explain to him
beforehand the nature and marvellous powers of the
harpsichord; and, having no idea of sound, this instru-
ment with colours could not suggest to him any
musical impressions. The purpose of the machine

1 [Consumer le fiers, le qitart ct Us peasants; literally, "the third,
the quarter, and the passers-by."]

APPENDIX 241

angle of a cube, which presses on his hand in an
irregular manner, is to appear to his eyes what it
appears in the cube.

Our above-quoted author, who founds his opinion
on Cheselden's experiment, inclines to believe (and
with reason) that a person born blind must at first
see all objects in a very confused manner, and that,
so far from distinguishing the globe from the cube,
he "Will not have a distinct perception of the two
different figures. He believes, however, that in the
long run, and without the assistance of touching,
the new spectator will learn to make a distinction
between the two figures. The reason which he
alleges, and that cannot be easily refuted, is that,
the blind person not being necessitated to employ
his touch to distinguish colours one from another,
the limits of colours will at length suffice to teach
him how to discriminate the form and the contour ot
different objects. In fine, he will see a globe and a
cube ; that is, a circle and a square. But the tact,
or sense of touching, having no relation whatever to
that of sight, he will not be able to guess that one
of those bodies is what he calls a globe and the
other a cube : so vision will by no means recall to
his memory a sensation which he had received by
the tact. Let us now suppose him to be told that
one of these two bodies is what by tact he felt to
be a globe, and the other a cube : will he be able
to distinguish them? The answer given by our
ingenious author is, that an uninstructed and grossly
ignorant person would hastily pronounce at all

16

2 4 2 DIDEROTS PHILOSOPHICAL WORKS

events ; but that a metaphysical or geometrical
mind, such as Saunderson's, would proceed with a
cautious examination of those figures ; and when,
by the supposition of certain lines therein, he would
find that he can demonstrate In the one all the
properties of the circle which he had learned by
the tact, and in the other all those of a square, he
would immediately be tempted to pronounce, " That
is the globe, and this is the square." However, if
he be prudent, he will be dubious of giving so pre-
cipitate a judgment, and thus reflect within himself :
"Perhaps, on an application of my hand to these
two figures, they will be mutually transformed one
into the other, so that the first figure might serve
for my demonstrating the properties of a circle
to blind folk; and those of a square, to such as
can see."

But a Saunderson would reply in the negative :
* * I am in error : they to whom I demonstrated the
properties of a circle and a square, in whom the
faculties of seeing and hearing perfectly agreed,
understood me very well, although they did not
touch the figures upon which I made the demon-
stration : they were satisfied with seeing them.
They did not see a square when I felt a cube : no ;
for If they had, we should never have understood
each other. But since they all understood me, it
Is clear that all men see alike. Therefore I see a
square what they saw a square and I felt to be a
square ; and by a parity of reason, I see a circle
what I felt to be a circle."

APPENDIX 243

We have here, in complaisance to our quoted
author, substituted circle to globe, and square to
cube ; because there is much reason to believe that
he who makes use of his eyes for the first time sees
nothing but surfaces, and knows not what projection
is ; for the projection of a body consists in some of
its points being more advanced towards us than
others. It is then by experience jointly with the
tact, and not the sight alone, that we are enabled to
judge of distances.

From all that has been said of the globe and the
cube, or of the circle and the square, let us conclude
with our author, that there are circumstances where
the reasoning and experience of others furnish a
new perspicuity to the faculty of seeing through
its relationship with the tact, and give assurance
to the eyes that they are in perfect harmony with
each other.

The letter-writer concludes with some reflexions
on what might be the case of a person who should
have seen from his birth, but was deprived of tact
or feeling ; and of another, in whom the senses -of
feeling and seeing should be in a perpetual contra-
diction with each other. But in order to avoid pro-
lixity here, we refer our readers to his reflexions ;
but which recall to our memory another, made by
him in the middle of his work, and of the same
tendency, viz. : C( If a person," says he, " who had
seen but for a day or two, were to find himself in the
midst of a blind people, he must take the resolution
either of holding his tongue, or of passing for a fool ;

244 DIDEROTS PHILOSOPHICAL WORKS

because every day he would think he was communi-
cating some new mystery, and such only to them,
but which their choice spirits would treat with
contempt. The advocates for, and defenders of,
religion might perhaps derive some advantages from
their cause from an incredulity so obstinate and so
ill-grounded. "

With this reflexion we close the present article ;
and it is sufficient to counterbalance several others,
scattered throughout the work, that indeed seem to
border on infidelity.

INDEX

Algebra (see Elements of Algebra).

Article, the origin of the definite,
182-184, 2I 6.

Augustine, St., 60.

Aveugle (article in the Encyclo-
pedia}, 13, 226-244.

Batteux, Charles, Abbe, 23, 209

note.
Berkeley, George, Bishop of

Cloyne, 104.
Bernis, Frangois Joachim de

Pierre de, Abbe, 205-207,

216.

Bible, tne authenticity of, 52-53.
BufTon, George Louis Leclerc,

Comte de, 2, 237.

Calculating machines, Saunder-
son's, 90-99, 219, 233-

234.
Castel, Father, his ocular music,

170-172.

Characteristics, 221.
Cheselden, William, 7, 125, 132,

225, 237, 239, 241,
Cicero, 55-56, 67, 180-182.
Clarke, Samuel, no.
Condillac, Etienne Bonnot de, 7,

24-25, 104-105, 119-120,

122, 126, 133, 223-225.

d ! Alembert, Jean le Rond, 3, 5,

137, 226.

tfAleniberfs. Dream, 4.
Darwin, Erasmus, I.
Daviel, Jacques, 144-145.
Deaf and dumb alphabet, 8-9,

89-90.
de Puisieux (see Puisieutf , Madame

de),

24S

de Reaumur (see Reaumur).

de Salignac (see Salignac, Melanie

de).
Descartes, Rene, 34, 64, 73, 102,

203.
Design, argument from, 5-6, 10-

15, 3 6 ~39, 109-114.
de Vandeul (see Vandeul, Madame

de).

Diderot, Denis, life of, 1-4.
English influence on, 2.
works, 2-4.
Didymus of Alexandria, 108,

220.

Dioptrics, 73.

Elements of Algebra, 8, 16, 17,
99, 104, 106, 234.

Elements of the Philosophy of
Newton, 7, 225.

Encyclopaedia, 3, 6, 23, 226.

Essay concerning Human Under-
standing, 222-223.

Essay on Merit and Virtue (see
Inquiry concerning Virtue
and Merit).

Essay on the Origin of Human
Knowledge, 7, 104-105,
119, 122, 126, 224.

Eusebius the Asiatic, 108.

Fine Arts reduced to a Singh
Principle, 23, 158, 208.

French language, 190-191, 217-
218.

Galileo, 102.

Gesture-language, 25, 163-167,

175, 214.
Gregory the Great, 52.

246 DIDEROT 'S PHILOSOPHICAL WORKS

Harmony in music, 217.
Harmony of style, 192-193.
Hebrew language, 203-204 .
Holmes, Gervase, 10, 18-19,

108-114.
Homer, 199-203.

Inchlif, William, 115-116.
Indiscreet Jewels, 2, 20, 23.
Inquiry concerning Virtue and

Merit i 2, 19.
Inversion, in language, 160-163,

176, 178, 180-182, 189-
.. 192-

Julian, edict of the Emperor, 50-
52.

Lamarck, Jean Baptiste Pierre

Antoine de Monet, Cheva-
lier de, 1-2.
Language, development of, 215-

216.
Leibniz, Gottfried Wilhelm, 110-

III.

Le Sage, I74-I7S-
Letter of Mr Gervase Holmes to the

Author of the Letter on the

Blind, 19.
Letter on the Blind, 2-3, 6-15,

20, 23-24, 68-141, 158,

227.
Letter on the Blind> Addition to,

142-157.
Letter on the Deaf and Dumb, 3,

23-25, 160-218.
Life of Saunderson, by Dr Inchlif,

10, 115-116.
Locke, John, 9, 64, 119-120, 221,

224-225.
Longinus, 201-202, 216.

Memoirs of the Life and Character
of Dr Nicholas Saunderson
(in Saunderson's Algebra},
16-17.

Method of Fluxions applied to a
Select Number of Useful
Problems, 17.

Miracles, 53-62.

Molyneux, problem of, 118-123,

222-223, 240-243.
Montaigne, Michel de, 41 -43, 64,

140.

Montgeron, Corre de, 60-62.
Muet de convention (theoretical

mute), 24-25, 163-166,

214-215.

Natural History, 237.

Newton, Isaac, 7, 15, 34, 102,

IIO-TII.
Nicaise of Mechlin, 1 08, 220.

Pascal, Blaise, 32.

'Philosophic Thoughts, 3, 4-6, 20,

27-67.
Puisaux, the blind man of, 8, 69-

81, 228-232.
Puisieux, Madame de, 6-7, 19-20.

Racine, Jean, 205-206.
Reaumur, Rene Antoine Fer-

chault, Seigneur de, 7, 20,

68-69, 137.

Saint- Hilaire, Geoffroy, i.
Salignac, Mlanie de, 146-157.
Saunderson, Dr Nicholas, 7-8,

10, 13, 15-19, oo-"6,

137-138, 232-236.
Sceptic's Walk, The, 3, 6.
Select Parts of Professor Sounder-

son's Elements of Algebra,

17-

Shaftesbury, Earl of, 221.
Symbolism in poetry, 195-200,

208.

Thoughts on the Interpretation of

Nature, 4, 12-13.
Transformism, I, 11-13, 111-114.
Treatise on the Sensations, 24-25)

224-225.
Treatise on Systems, 105, 119,

132, 224.

Vandeul, Madame de, 20.
Virgil, I97-I99.

Voltaire, Francois-Marie Arouet,
7, 14, 225.

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