Diderot, Interpreter of Nature:
Selected Writings

Translated by Jean Stewart and Jonathan Kemp
Edited and with an introduction by Jonathan Kemp


IN 1936 on the Fourteenth of July, the anniversary of the storming of the Bastille, the historic site in Paris was decorated for the huge Popular Front demonstrations with monster portraits of great Frenchmen of the Revolution of 1789. Among those honoured by this great political movement of human emancipation and defence against Fascism, was Denis Diderot.

What does Denis Diderot mean to‑day, in the present situation of social flux? Were these Frenchmen, members of the Radical, Socialist and Communist Parties, leading French writers and scientists, celebrating only a past triumph and its heroes? Or does Diderot mean something more? Does his creative genius and passionate humanity still exert influence? Who are his spiritual heirs?

The masterpieces of world literature have a permanent value, however far we may be from the period and conditions that gave rise to them. Until recently Diderot has been read and studied almost exclusively as literary artist, man of letters, editor of the Encyclopedia and writer on aesthetics, expressing more vividly than any other writer the thought of the Age of Enlightenment and the intellectual atmosphere which prepared and reflected the great French Revolution of 1789. Thus Diderot could be studied academically, as a museum‑piece, and a post‑mortem dissection made of his work for the light it throws on the intellectual ferment of that pregnant epoch, when the bourgeoisie was a revolutionary class engaged in the overthrow of feudalism.

In preparing this selection of Diderot's writings, the object was not, however, that they should be read only from this [1/2] aspect, as marking the greatness of a past age. Diderot himself wrote:

“This is the fate of all men of genius: they are not at the level of their own time, they write for the succeeding generation.” *

In retrospect we know that Diderot himself did indeed write for his own time, preparing men’s minds for the revolution which he did not live to see. But he was also writing for succeeding generations; his work has a practical value more evident to‑day than for many years past. The study of dialectical materialism, the philosophical basis of revolutionary Marxism, is reaching a greater magnitude than ever before in this country, while another social revolution is maturing. Modern dialectical materialism and the new humanism of Marxism is the spiritual heir of Diderot.

Diderot is one of the great line of materialist philosophers; his successors were Feuerbach, Marx and Engels. This side of Diderot's work has been very little studied, and in general the importance of his philosophical work has been subordinated, by those who have studied him hitherto, to the other manifold aspects of his writings, and to the interest of his rich and vivid personality.

A primary object in preparing this selection of his writings was to assist the study of modern dialectical materialism. For this reason the notes in this book are confined almost exclusively to relating Diderot's work to more recent materialist writings. These notes are not intended to replace the full commentary on Diderot's philosophic work which could and should be undertaken by modern materialists, but are intended only as indications of points of contact and for further reading. Modern dialectical materialism has, of course, a developmental history like any other scientific law or generalization. Without a knowledge of the developmental stages in philosophy culminating [2/3] in the Marxian synthesis of dialectical materialism, the understanding of the latter is made unnecessarily difficult. It is like attempting to study modern atomic physics without knowing how the present state of development of the science was reached, without knowing the successive stages in the deepening and widening of scientific knowledge about the atom.

Writing on the necessity for natural science to recognize the dialectical character of natural phenomena, Engels said:

"It is, however, precisely the polar antagonisms put forward as irreconcilable and insoluble, the forcibly fixed lines of demarcation and distinctions between classes which have given modern theoretical natural science its restricted and metaphysical character. The recognition that these antagonisms and distinctions are in fact to be found in nature, but only with relative validity, and that on the other hand their imagined rigidity and absoluteness have been introduced into nature only by our minds—this recognition is the kernel of the dialectical conception of nature. It is possible to reach this standpoint because the accumulating facts of natural science compel us to do so; but we reach it more easily if we approach the dialectical character of these facts equipped with the consciousness of the laws of dialectical thought. In any case natural science has now advanced so far that it can no longer escape the dialectical synthesis. But it will make this process easier for itself if it does not lose sight of the fact that the results in which its experiences are summarized are concepts; but that the art of working with concepts is not inborn and also is not given with ordinary everyday consciousness, but requires real thought, and that this thought similarly has a long empirical history, not more and not less than empirical natural science. Only by learning to assimilate the results of the development of philosophy during the past two and a half thousand years will it be able to rid itself on the one hand of any isolated natural philosophy standing apart from it, outside it and above it, and on the other hand also of its own limited method of thought, which was its inheritance from English empiricism." (Engels. Anti‑Dühring, p. 19.)

Diderot marks one of the great stages of development in philosophy in general and in the philosophy of natural science. The study of his work is essential for the proper understanding of modern dialectical materialism. For [3/4] natural science itself Engels's characterization remains in large measure true, and the dialectical synthesis still awaits conscious general application. A beginning is now being made by those younger scientists who have discovered the liberating and co-ordinating power of dialectical materialism. Diderot's work is one of the cardinal stages in pre‑Marxist materialism.

For very good reasons, materialist philosophy is practically untaught in academic courses in philosophy; generally speaking, a materialist philosophy has been the ideological reflection and weapon of revolutionary classes. Always the forces of reaction against progress have viewed with horror any materialist, or "atheist" doctrines, and have fought their propagation with every weapon, from misrepresentation to physical terror. At the same time, some form of idealist philosophy together with religion and superstition has always been the ideological expression of non‑progressive classes or social groups.

To prevent confusion in what follows it is well to make certain that the meaning of materialism and idealism in philosophy is understood, since they are two words often used in quite another sense, the first as a term of abuse, and the second as a term of praise, by those wishing to misrepresent and defame the ideologists of revolution.

There is

“a traditional philistine prejudice against the word materialism resulting from the long‑continued defamation by the priests. By the word materialism, the philistine understands gluttony, drunkenness, lust of the eye, lust of the flesh, arrogance, cupidity, avarice, miserliness, profit-hunting and stock-exchange swindling—in short, all the filthy vices in which he himself indulges in private. By the word idealism he understands the belief in virtue, universal philanthropy and in a general way a ‘better world,’ of which he boasts before others, but in which he himself at the utmost believes only so long as he is going through the depression or bankruptcy consequent upon his customary ‘materialist’ excesses. It is then that he sings his favourite song, ‘What is man?—Half beast! Half angel!’” (Engels. Ludwig Feuerbach, p. 41.)


In philosophy the words materialism and idealism have quite different meanings from the perversions trenchantly described by Engels.

One of the great basic questions of philosophy is that concerning the relation of thinking and being, the relation of spirit or mind to nature. The differentiation of materialism from idealism in philosophy may be described as follows:

“The question of the position of thinking in relation to being, a question which . . . had played a great part also in the scholasticism of the Middle Ages, the question: which is primary, spirit or nature—that question, in relation to the church, was sharpened into this: ‘Did God create the world or has the world been in existence eternally?’”

"The answers which the philosophers gave to this question split them into two great camps. Those who asserted the primacy of spirit to nature and, therefore, in the last analysis, assumed world creation in some form or another . . . comprised the camp of idealism. The others, who regarded nature as primary, belong to the various schools of materialism. The two expressions, idealism and materialism, primarily signify nothing more than this." (Engels. Ludwig Feuerbach, p. 31.)

The distinction was understood in this sense also by idealist philosophers. Thus the view of the dialectical idealist Hegel was:

"Generally speaking, empiricism finds the truth in the outward world; and even if it allow a supersensible world, it holds knowledge of that world to be impossible and would restrict us to the province of sensation. This doctrine when systematically carried out produces what latterly has been termed materialism. Materialism of this stamp looks upon matter qua matter, as the genuine objective world." (Hegel. Enzyclopädie der philosophischen Wissenschaften in Grundrisse. Werke. 1843., vol. IV, 83. Quoted in Lenin, Materialism and Empirio‑Criticism. Collected Works. Vol. XIII, p. 99.)

The modern dialectical materialist interpretation of the relation of man's thinking to his own existence and to surrounding nature is shown in Lenin's words [5/6]

“Knowledge is the eternal infinite approach of thought to the object. The expression of nature in man's thought must be understood not in a 'dead' 'abstract' way, not without movement, not without contradictions, but in an eternal process of movement, of the springing up of contradictions and their solution.” (Lenin, quoted by Fox.)

Diderot was a materialist in this sense: he believed in the primacy of nature and derived the infinitely complex structure of the universe from the motion and organization of matter. Man is a product of nature and man's mind, his thinking, depends upon the existence of his body, and is a function of the brain or a reflection of the outer world. Diderot's philosophical development shows a consistent movement to this position (see p. 20) which he thenceforward held in his maturer work.

For the rest, let Frederick Engels, himself one of the great materialists and co‑worker with Marx in the development of dialectical materialism, write Diderot's epitaph:

"The conviction that humanity, at least at the present moment, moves on the whole in a progressive direction has absolutely nothing to do with the antithesis between materialism and idealism. The French materialists equally with the deists, Voltaire and Rousseau, held this conviction to an almost fanatical degree, and often made the greatest personal sacrifices for it. If ever anybody dedicated his whole life to the 'enthusiasm for truth and justice'—using this phrase in the good sense—it was Diderot." (Engels. Ludwig Feuerbach, p. 41.)

Many of Diderot's scientific conceptions have become out of date after nearly two hundred years; it could hardly be otherwise, since they were necessarily conditioned by the knowledge then available. Yet also germs and foreshadowings of what are now modern scientific ideas can be found in his work. He was always eager to understand and to incorporate into his writing the results of the most recent scientific work. Only a philosophy like Diderot's, an embryonic dialectical materialism, was able to grow and develop continuously; new scientific facts did not wreck [6/7] his "theory," but only provided a further enlargement of knowledge for the testing and shaping of his generalizations and his materialism based on the primacy of nature. His recognition of the dialectics of nature, clearly shown in the Conversation between d'Alembert and Diderot, and in D'Alembert's Dream placed him far in advance of the contemporary materialist philosophers who were seeking to work out consistently materialist theories of biological phenomena (see p. 30). His political and moral ideas bear the marks of his period; but here also many progressive conceptions reaching beyond his time may be found, which are real and living ideas for to‑day.

A coherent philosophic materialism; a dialectic method, only embryonic in the philosophic and scientific fields, but brilliantly developed in the social criticism of Rameau's Nephew; a militant and witty atheism; a constant urge towards the future sustained by a tremendous thirst for new knowledge, new ideas, and an intense love for humanity—these things characterize Diderot. They make him a living figure for to‑day when another major social revolution, an even more decisive movement of human emancipation, is maturing in all the capitalist states of the world. The modern revolutionary movement stands for the full use of science and industry for the benefit of all, for the corresponding free development of human thought; and against the tyranny of Fascism, with its destruction and thwarting of creative human thinking and against the horrors and waste of war. History has set before the modern working‑class the task of superseding capitalism and building socialism. All progressive and liberal thinkers must ally themselves with this revolutionary class of the mid‑twentieth century, as Diderot and his co‑workers did with the revolutionary class in their epoch, since it is the only class which can break the barriers that decaying capitalism places in the way of further human betterment. All those characteristic qualities of Diderot's genius, must find embodiment to‑day [7/8] in a correspondingly great intellectual movement, reflecting and helping the socialist revolution.


Only a brief sketch of the life of Diderot can be given here as an indication of the personal background of his work.

Denis Diderot was born at Langres, Haute Marne, France, in October 1713. His father was a cutler; the Diderot family had been artisans, some entering the Church, for more than a century. Diderot went first to a school conducted by Jesuits, where he proved himself a brilliant pupil. It was decided that he should enter the Church and an uncle was prepared to leave his living to him. At one period Diderot wished to forsake this career and become a cutler, but he returned to his studies and at the age of 12 was tonsured. For some reason unknown, the design that be should succeed to his uncle's living was vetoed by the Chapter. When the time came to leave school Diderot was determined to continue his studies and made secret preparation to go to Paris, possibly with the connivance of the Jesuits. When this was discovered by his father the latter agreed that he should continue and took him to Paris where he entered the Jesuit college of Louis‑le‑Grand. He was a brilliant student and obtained his master of arts degree. But his feelings for the religious vocation had cooled, probably because the contacts he made and the free discussions he heard in the capital city showed him that there were wider fields for his abilities and developing tastes than were offered by a career in the Church. He began to study law; this was about 1730.

About the next formative ten years of his life practically nothing is known. There is evidence that his father refused further support because of his failure to continue at law. His mother supplied the deficiency as much as possible, sending a servant on foot several times to Paris with money [8/9] for him. It Is conjectured that he led a very bohemian life at this time, doing odd jobs of teaching, translating and writing, living on credit and probably also getting money by fairly dubious means, as was the lot of many of the writers of the Enlightenment.

Nothing is known of his intellectual development during this period, but it is evident that he must have mixed with the crowd of writers and thinkers who were the intellectual expression of the maturing revolution. He must have read widely in Voltaire, Locke, Montaigne, Montesquieu, Toland and other progressive and freethinking writers, for the first personal work that is known to be his is a translation and adaptation, appearing in 1745, of Shaftesbury's Inquiry Concerning Virtue. In this Diderot clearly showed that he had emerged from the deadening bonds of religious dogma (see p. 21).

Diderot frequented the cafés, gardens and book‑sellers where the intelligentsia of Paris met and discussed all the questions of that period of intellectual ferment, making many friends among them and rapidly becoming one of the foremost.

He married Antoinette Champion in 1743. His life with her was not happy, chiefly owing to differences in temperament: Diderot, bohemian, brilliant and short of money, his wife no doubt embittered by domestic insecurity and burdened by housekeeping cares, unable to understand or appreciate his interests. Diderot lived by doing badly‑paid translating work. In the winter of 1746 the publishers for whom he worked, knowing him to be almost penniless, proposed that he should undertake the translation and adaptation from the English of Chamber's Encyclopedia, which they wished to publish in conjunction with the printer Le Breton. Diderot was only too glad to have the opportunity to get a regular wage.

It is evident that the offer of this work was the nucleus that was needed to crystallize all the ideas and discussions [9/10] that Diderot had had with his friends of the group known as the "philosophers," who represented the ideological front of the coming revolution. It is only necessary to mention Voltaire, Rousseau, Condillac, d'Alembert, Condorcet, Montesquieu, Fontenelle, Buffon, Daubenton, d'Holbach, Helvétius, Gassendi, Galiani, Raynal, to indicate the brilliant quality of the flower of intellectual France, which, in one way or another, made up the liberating movement of the Enlightenment. Most of these, with many others, Diderot was able to enlist in the production of the Encyclopedia.

If ever a man seized an opportunity and brilliantly exploited it to forward an ideological revolution that man was Diderot. He planned and directed the writing of the Encyclopedia so that it became the beacon and the monument of the Age of Reason, and a unique intellectual achievement. How well this work was suited to the man and the man fitted for the work is shown by this, that the direction and production of the Encyclopedia became the main theme of Diderot's life for the next twenty years. Until beginning the Encyclopedia when he was thirty‑three, Diderot's life had been like that of any of his circle; much reading of the new work that was being produced, much discussion of social, moral, philosophic and scientific problems, translating to make a living and some writing. In the project of the Encyclopedia Diderot seems to have recognized his lifework, which be thenceforward pursued with a tenacity rarely equalled.

The Encyclopedia was begun in 1746 and for the next twenty years there was a struggle of varying intensity against the often violent attacks of reaction, led by the Jesuits, before the work was completed. During this long period many contributors withdrew their support through fear and discouragement, the chief one being d'Alembert, who had been co‑director with Diderot. The latter kept to the work to the end, and when it became necessary, organized the [10/11] illegal printing and distribution of the last volume. He did not follow the advice of Voltaire to emigrate and finish the work abroad. There is no space here to describe more fully the extremely interesting history of the Encyclopedia, reflecting as it does the conflicting forces and cross‑currents in the contemporary class‑struggle. The Encyclopedia was completed only through the energy, courage and tenacity of Diderot.

At the period of the beginning of the Encyclopedia, Diderot published work of his own which involved him in trouble with the authorities. The Philosophic Thoughts (1746) was condemned and publicly burnt. He wrote the Promenade of a Sceptic (1747) which was denounced to the police, who searched for, but could not find, the manuscript. The denouncer was the abbé Pierre Hardy, curé of Saint Médard, who said that Diderot was "a man without any accomplishments, who played the wit and gloried in blasphemy." Diderot changed his dwelling‑place, and wrote the essay on The Sufficiency of Natural Religion. Other work, particularly the Letter on the Blind, for the Use of Those who See (1749), and allegations about still other "dangerous writings" brought further police interference.

The police were active everywhere then, repressing by terror the rising popular anger against the increasing taxation needed to pay for the Seven Years' War, the luxury of the Court and the extravagance of the King's mistress, Madame la Pompadour.

Many writers and learned men were imprisoned in the Bastille and elsewhere, often without trial, for indefinite periods under a lettre de cachet. Similar repressive measures in India at the present time enable us to visualize the conditions in France under which Diderot worked. The French monarchy during Diderot's lifetime used repression by terror against the progressive intellectuals, among whom the group of "philosophers" around Diderot and d'Holbach were in the forefront. At that stage of historical development [11/12] the bourgeoisie was a revolutionary class, working for the overthrow of feudalism, which was preventing the fuller development of human potentialities. To‑day the bourgeoisie has developed to its limit in the capitalist class, and further advance demands, in turn, its supersession. Capitalism, especially as expressed through Fascist governments as in Italy, Germany and elsewhere, now plays the role of the French monarchy of Diderot's time. The repression of all the liberal and progressive thought which is the ideological weapon and reflection of the modern revolutionary class, the workers and their allies; the curtailment of civil liberties; all these features with which we are acquainted in this period of decaying capitalism, make real to us the conditions under which Diderot and his co-workers had to carry on the work for which they are honoured to‑day as great emancipators of humanity. The repression used by the French monarchy was less well organized than it is to‑day in Fascist countries; among other reasons because the historical stage had then been reached when the ruling class no longer knew how to rule and was itself internally divided and beginning to disrupt. Many of its own servants were untrustworthy and gave help to the progressive movement.

Diderot, who was looked upon as one of the leaders (a police‑agent said that he was "a clever fellow, but extremely dangerous") was among those arrested. He denied authorship of everything of which he was accused, except the Promenade of a Sceptic, which he acknowledged. With the prospect of seeing the Encyclopedia destroyed at birth and his family reduced to poverty, he appears to have made humiliating vows and promises. For this, and in default of any concrete evidence against him, he was released after three months, and allowed to continue with the direction of the Encyclopedia, but always under the difficulty of writing and editing so that it should pass the censor (see p. 16).

In 1773, after the completion of the Encyclopedia, Diderot [12/13] travelled to the court of Catherine II of Russia, who had bought his library from him in 1767, allowing it to remain with him during his life‑time. He returned to France in 1774 and the remaining ten years of his life were relatively uneventful, with the temporary easing of the social tension after the death of Louis XV, during the beginning of the reign of Louis XVI, although there is evidence that the police were still anxious to embroil him. Thus Restif de la Bretonne, in his autobiography Monsieur Nicolas under the date 1775‑6, when describing his own troubles with the police censorship says:

“I received a note from the police‑agent Desmarolles, ordering me to come to his office. He told me that the sale of The School for Fathers was suspended; and that a new secret censor had been appointed to examine it with extreme rigour. 'Your Paysan,' he added, ‘has already caused enough trouble. A magistrate has written to me about it; here is his report: “This is a coherent and unified system of philosophy for overthrowing all religion, all morality' . . . etc.”’

“This magistrate was the famous d'Epresmesnil, who, having imagined that the work was by Diderot, wished to involve the philosopher in a quarrel with the Parlement.” (Restif de la Bretonne. Monsieur Nicolas, X, 136.)

The police interference apparently came to nothing, however, and Diderot was left alone. He died in 1784, five years before the outbreak of the revolution of which he was the highest ideological expression.

The best biography of Diderot is probably that by André Billy (1932) which uses newly discovered material. This book is concerned almost exclusively with his personal life and is not a study of his philosophical work.

The study of Diderot by John Morley (1878, 1886), is the best available in English and is on the whole sympathetic at least to Diderot the man, but much hampered by Victorian prudishness. It does not give prominence, for this reason, to the most mature of Diderot's philosophical [13/14] writings, (e.g., the Conversation between D'Alembert and Diderot, and the complementary pieces and other dialogues) nor is it able to show Diderot's work as one of the great stages in the development of materialism; rather it tries to explain away or to excuse his atheism and materialism.

There is an interesting and very appreciative essay on Diderot in The New Spirit, by Havelock Ellis. The only study of Diderot's philosophy from the point of view of modern dialectical materialism is that by I. K. Luppol (1936). Another study of Diderot, by Jean Luc, is announced in the same series, Socialisme et Culture, as Luppol's book. For the bibliography, see p. 357.


The production of the Encyclopedia formed the main thread of Diderot's activity during more than twenty years of his life. He intended that the Encyclopedia should be an organized whole, embracing all the sciences, not as so many unconnected fields of knowledge, but in their interconnections, showing the ways in which one science was related to another, the ways in which science was investigating all the various parts of nature, and the impossibility of understanding a few isolated parts without reference to the whole.

The Encyclopedia was to apply consistently the principle of freedom of thought and criticism of authority. Further, it was aimed to give complete descriptions of the arts, crafts and manufactures of the period, thus giving a detailed picture of contemporary industry. It was intended that the Encyclopedia should be not simply a work of reference for specialists but rather an instrument of universal education, and to this end the articles were deliberately written so that the trades, sciences and philosophy should be accessible to everybody. The Encyclopedia was deliberately planned to be of great social significance, and shows Diderot, in the historical conditions, under a despotic monarchy, as [14/15] a creative genius of brilliant imagination and foresight, admirably reflecting the revolutionary ideological forces that were ripening within the effete social structure. Besides the general directing and editorial work, Diderot himself contributed many articles, dealing particularly with the history of philosophy, and with mechanical arts and crafts. For the latter, he spent much time studying them practically in the workshops, and supervised the making of the drawings for the three to four thousand plates illustrating the work. The artisan tradition of his family, of which he was very proud, stood him in good stead here, and it was characteristic of him that he studied the crafts and manufactures practically, as well as by voluminous reading. Björnstahl, a Swedish professor who met him at the Hague in 1774 on his return from Russia, records interesting details illustrating the practical side of Diderot's character. Björnstahl said:

"He has views extending over an incredibly wide field, possesses a vivacity I cannot describe, is pleasant and friendly in intercourse, and has new and unusual observations to make on every subject. Who could fail to prize him? He is so bright, so full of instruction, has so many new thoughts and suggestions, that nobody can help admiring him. But willingly as he talks when one goes to him, he shows to little advantage in large companies, and that is why he did not please everybody at St. Petersburg. You will easily see the reason why this incomparable man, in such companies, when people talk of fashion, of clothes, of frippery and all other sorts of triviality, neither gives pleasure to others, nor finds pleasure himself. . . . He often told me that he never found the hours pass slowly in the company of a peasant, or a cobbler or any handicraftsman, but that he had many a time found them pass slowly enough in the society of a courtier. 'For of the one,' he said, 'one can always ask about useful and necessary things, but the other is mostly, so far as anything useful is concerned, empty and void.'" (Quoted in Morley's Diderot, Vol. II, Chapter IV.)

Diderot studied science practically in the laboratory of Rouelle, who was Lavoisier's teacher.

Owing to the necessity, if the Encyclopedia were to be [15/16] produced at all, of avoiding interference by the censorship, the articles for it had to be written very circumspectly. Furthermore, the large number of contributors drawn upon did not all hold identical political and social views. It was the co‑operative effort of a "united front" of progressive thinkers with the main general objective of enlightenment in all fields of knowledge.

For these reasons the Encyclopedia articles do not always live up to the high standard planned in the Prospectus. In correspondence with Voltaire, d'Alembert put forward various reasons for the blemishes which the former found in the Encyclopedia. He explained that Diderot was not always in a position to reject and prune articles that were offered him, for reasons of general expediency. A writer who was valuable for some excellent articles might insist, as the price of good work, on the inclusion of some of his bad work, too:

"No doubt we have bad articles in theology and metaphysics, but with theologians for censors and a privilege,** I defy you to make them any better. There are other articles less exposed to the daylight and there everything is repaired." (Quoted by Morley, op. cit., Vol. II, p. 142.)

The tyranny of ecclesiasts and ministers made dissimulation necessary, and a veil had to be drawn over direct expressions of opinion and criticism, the writer's true opinions being revealed by

“a piquant phrase, an adroit parallel, a significant reference, an equivocal word of dubious panegyric.” (Morley, op. cit. II, p. 143.)

In the article "Encyclopédie" Diderot himself said:

"In all cases where a national prejudice would seem to deserve respect, the particular article ought to set it respectfully forth, with its whole procession of attractions and probabilities. But the edifice of mud ought [16/17] to be overthrown and an unprofitable heap of dust scattered to the wind, by references to articles in which solid principles serve as base for the opposite truths. This way of undeceiving men operates promptly on minds of the right stamp, and it operates infallibly and without any troublesome consequences, secretly and without disturbance, on minds of every description."

And d'Alembert, in a letter to Voltaire, wrote: “Our fanatics feel the blows, though they are sorely puzzled to know from which side they come.”

An example of the wrapping up of revolutionary content in disarming externals is given later p. 48). In addition to all the above reasons which contributed to emasculate the Encyclopedia, there were further crude mutilations of articles by the printer Le Breton himself, who feared the consequences of printing the more dangerous pieces.

For all these reasons the Encyclopedia does not give the clearest picture of the revolutionary thinking of the period. This is found in the books printed secretly or abroad (e.g., Helvétius, d'Holbach). Much of Diderot's best work was not printed during his life‑time but circulated in manuscript copies among his friends and the subscribers to Grimm's manuscript Literary Correspondence.

In spite of all the shortcomings imposed by the conditions under which it was produced, the Encyclopedia remains a monument to Diderot's organizational ability and energy, and his foresight with regard to its objective showed deep social consciousness. Diderot's articles contributed to the Encyclopedia fill four volumes of the collected edition of his works.

The most brilliantly imaginative and creative of Diderot's writings, however, are to be found in the other sixteen volumes of the collected works, which contain the pieces written without fear of the censor. For the convenience of description this work may be divided into several groups, although it is truer of Diderot than of many other writers of such capacity and many‑sidedness, that all the elements, [17/18] scientific, philosophical, literary, artistic and critical, are fused harmoniously in all his work.

He left about four volumes of criticism, principally on painting, with some on sculpture and music. His criticisms of the Salons of 1759 to 1771, are famous and practically founded art‑criticism. He wrote critical essays on dramatic and literary theory, such as the Reflexions on Terence, the Eulogy of Richardson, the Paradox of the Comedian, and a treatise on Dramatic Poesy.

To support his severe criticism of the artificiality of the contemporary French theatre, he wrote several plays of naturalist flavour. The rule of his taste and of his art was that it should be natural, living. The plays are the least good part of his work.

His extraordinary realistic novel La Religieuse and the satirical Jacques the Fatalist outwardly modelled on Tristram Shandy are well known by name, if not by their content.

The Indiscreet Toys (Les Bijoux Indiscrets) was described by Carlyle as "the beastliest of all past, present and future dull novels" and he recommended "the next mortal creature, even a Reviewer, to bathe in running water, put on a change of raiment, and be unclean until the even." Morley could not bring himself to name its title, and dismissed "this tale as the lees of Diderot's strong, careless, sensualized understanding," . . . "the vein of defilement." (Morley. op. cit., I, 75.) The Indiscreet Toys, although in form a frivolous “gallant” novel of the type of the younger Crébillon, is much more than merely that. It contains satirical criticisms of the abuses and morals of the Court and its satellite society, of religious prejudices and corrupt personalities, veiled by its setting in a fabulous Eastern country. The chapters we have selected (see p. 35) clearly show that Diderot put serious content of high order even in a romance of "gallantry" written chiefly to obtain money for his mistress. He himself entitled the brilliant allegorical Chapter XXXII. "Perhaps the best and the least read in this book," and was evidently fully [18/19] conscious of its value. It is an interesting index of his philosoph,c development that at this early stage, 1748, when he was thirty‑five, he looked to the development of natural science, to practice, as the critic of all philosophies (see p. 42). The chapters from The Indiscreet Toys printed here adequately neutralize Carlyle's and Morley's hysterical criticism.

Diderot's introduction of profound content under a gay form is typical of the whole of his writing; he has expressed this attitude in a letter to Sophie Volland (see p. 331). A fairly large volume of Diderot's correspondence is preserved (Oeuvres Complètes, Vols. XVIII, XIX, XX) the most remarkable part of it being the series of letters to Sophie Volland. [Lettres à Sophie Volland, edited by André Babelon, (1931) contains newly discovered letters, not included in the Oeuvres Complètes of Assézat and Tourneux, which bring the total to 187].

The letters, covering the period 1759‑1774, are one of the masterpieces of French, if not of all, epistolary literature. In Sophie Vollard, Diderot found someone to whom he could reveal every side of his manifold nature. "My Sophie is both man and woman when she pleases," he wrote, and into his letters to her went everything that was in his head," narrating the incidents of the day, telling what he was thinking about or projecting, repeating current scandal or sometimes a not quite decent story, flashing instinctively into wise or witty reflection; always with a swift, almost unconscious pen, forgetting now and again what he had already said." (Havelock Ellis. The New Spirit, p. 49.)

The last and most important group of work is that comprising the more directly philosophical and scientific writings, although, as already mentioned, the scope of these is extremely wide and embraces moral, social, sexual, philosophical and scientific problems, not treated didactically, but extremely freely in a typically spontaneous [19/20] manner. Diderot's favourite and characteristic form was a dialogue between two or three people. He was a brilliant talker and this is clearly reflected in the profusion and rapid succession of ideas that are introduced into these pieces, and in the tremendous élan with which they are carried forward.

Probably the most remarkable are the Conversation between d'Alembert and Diderot with the complementary D'Alembert's Dream and the Conclusion (p. 49 et seq.), and Rameau's Nephew (p. 235). Here in small compass is expressed the quintessence of Diderot's genius. Diderot himself said that the d'Alembert group of dialogues were the only writings of his own, together with a mathematical memoir, with which he was content.

The writings chosen for this selection are taken principally from the group of philosophical and scientific writings, and need not therefore be described; they speak eloquently for themselves in a way that Diderot has known best how to use, clothing profound thought in brilliant dialogue.


Diderot nowhere expounded his philosophic ideas formally, nor sought to embody them in a system; this would have been entirely contrary to his character and to his mode of working. Consequently the understanding of his philosophic position must be built up from passages, phrases, and comments scattered prodigally throughout his writings. This task has barely been begun by modern dialectical materialists, who are the real heirs of Diderot in philosophy. The following brief sketch of Diderot's philosophic evolution is based on the study by I. K. Luppol (1936), and will serve to connect the earlier writings of Diderot with the maturer work which is reproduced here.

The Encyclopedia article on philosophy (appearing in 1757) might have been expected to give an opportunity for a formal definition and exposition of Diderot's conceptions. [20/21] But what is found there, however, is only the then current Wolffian metaphysical view and classification of philosophy. The conclusions which Diderot is known from other work to have reached during the previous twelve years are not given. Luppol (op. cit.) concludes that the Encyclopedia article must be considered simply as intended to show the average contemporary view of philosophy in mid-eighteenth century, and not in the least to represent Diderot's personal view.

Furthermore, the necessity to avoid police interference, which led to much dissimulation, as already described, must be remembered. Any clear‑cut statement of Diderot's views as they were in 1757, must have led to suppression, as proved by the condemnation of the relatively mild Philosophic Thoughts in 1746. An article on "Philosophy" would have been the obvious place for a censor to look for “dangerous writing”; hence only the most ordinary material was put there.

Diderot elaborated his philosophy fragmentarily through a number of years, in a series of writings, basing himself eventually on the early materialists (Epicurus, Lucretius) and the facts of contemporary science, but only after a process of criticism of religious and philosophical doctrines.

The evolution of his ideas begins with the adaptation and translation of Shaftesbury's Inquiry Concerning Virtue; Diderot's adaptation appeared in 1745. In his preface, Diderot proposed to show that virtue was related to the knowledge of God and that the earthly happiness of man was inseparable from virtue. What Diderot found uncomfortable about religion was, however, the fanaticism to which it gave rise. He felt that "religion . . . practised with enlightened zeal could not fail to encourage moral virtues." Barbarous fanatics only knew the ghost of religion.

"All the efforts of unbelief were less to be feared than this inquisition. Unbelief combats the proofs of religion; this Inquisition seeks to destroy them. . . . Recall the history of our civil disturbances and you will see one half of the nation batheing, out of piety, in the blood [21/22] of the other half, and violating the most primitive feelings of humanity in order to uphold the cause of God; as if it were necessary to cease to be human in order to show one's self religious!" (Introduction to " Essay on Merit and Virtue," Oeuvres Complètes, I, p. 10.)

The religious events of his time precipitated Diderot's rupture with Catholicism. He was disgusted much more by the fanaticism of bigots, princes and servants of the Church, than he was repelled by the lack of faith of the unbelievers.

"It was necessary to free belief in God from the prejudices with which the fanatics were overwhelming it, and to put it in agreement with the science of man, to infuse it with the spirit of tolerance." (Luppol. op. cit., p. 117)

In 1745 Diderot still retained a belief in most of the Christian dogmas, but suspended judgment with regard to revelation, wishing to obtain direct proof of it. Thus he was then a theist, believing in the existence of God, the reality of moral good and evil, the immortality of the soul, the idea of recompense and future punishment; he was not yet a deist, a term introduced by Shaftesbury to distinguish from theists those who denied revelation while accepting the other dogmas of the theists.

Diderot used the idea of relative, as against absolute good and evil, thus renouncing orthodox Christian conceptions on this matter. He closely united particular interest, the personal happiness of each individual, to the happiness of all. Virtue is the search for happiness by contributing to the happiness of others; vice is the opposite attitude and has evil as a result. This was Shaftesbury's view and was accepted by Diderot in 1745. At the same time Diderot recognized that atheists were not malefactors. He saw acknowledged atheists living honest lives without expectation of recompenses or punishment in an after‑life to keep them to the straight and narrow path, which he at [22/23] first had thought could be pursued only with the aid of a belief in God—"there is no virtue without a belief in God."

Life itself, in the persons of these atheists, showed Diderot that virtue, which he founded on religious faith, could be self‑sufficient; virtue could do without the support of religious belief; an atheist could be virtuous. This was a great advance, and the next stage is represented by the Philosophic Thoughts (1746) in which the clear break with orthodox Christianity was made.

The Thoughts were intentionally fragmentary and disconnected; on the whole they are a series of reflections in which on the one hand, deist, and on the other, atheist arguments are put forward. Diderot was still concerned with theological questions; the questions of religion were the most pressing to him at that time, and this was the field in which the social question, the pre‑revolutionary ideological struggle, was discussed in its most open form.

In the Thoughts Diderot passed beyond the theism of the Essay.

"Why demand of me that I should believe that there are three persons in God, as firmly as I believe that the sum of the three angles of a triangle is equal to two right angles? Every proof must produce in one a certitude proportional to its degree of strength; and the action of geometrical, of moral and of physical demonstrations on my mind must differ or the distinction is frivolous. . . ." (Philosophic Thoughts, § 58.)

Miracles were not proofs to a man who could talk like this about the Trinity. 

"What is God? is a question which children are asked and which philosophers find great difficulty in answering. One knows at what age a child ought to learn reading, singing, dancing, latin, geometry. Only in religious matters is their capacity not consulted; they can no sooner hear but they are asked: What is God? It is at the same time, and from the same lips, that they learn that there are fairies, ghosts, ogres and a God." (Philosophic Thoughts, § 25.) 


In the Philosophic Thoughts Diderot was working slowly forward to solve the religious and philosophic questions, giving attention to the arguments of each trend of opinion, concluding nothing hurriedly, but observing, reflecting, and testing each conclusion. He maintained as yet no one point of view, and was neither Christian, deist nor atheist. He was at a transitional stage, not a sceptic who ends by doubting, but an inquirer who begins by doubting and investigates to get knowledge; a truly scientific investigator. He recognized that atheism was the most powerful rival of deism. Atheism used arguments of a physical and cosmological kind, and against these the deists usually brought forward moral arguments. But Diderot found it necessary to introduce arguments of physical and cosmological type also to support the deist position—evidence of “design” in nature, and the authority of Newton and other learned men who had "found satisfying proofs of the existence of a sovereign, intelligent Being" (Philosophic Thoughts § 18) in the amazing complexity and organization of nature. The teleological “proof” of the existence of God was abandoned by Diderot when he later studied chemistry, physiology and mechanics; the element of wonder, incomprehension, dissolved before the investigations of science and the knowledge and understanding which later scientific developments brought (see On the Interpretation of Nature, p. 43)

The Promenade of the Sceptic, or The Garden‑Walks appeared in 1747. The action takes place in a vast garden, and the people in the various garden‑walks represent different people in theological and philosophical schools.

In the Thorn Walk, pious people wandered, clothed in white, with their eyes bandaged. Although thus blinded they are forbidden to tear or soil their garments (sin); in bad cases soap is sold to them (absolution). In the Chestnut Walk are the various schools of philosophers, the principal discussion concerning the existence of a God; how [24/25] to represent Him if there is one, and why not do without one? This is the most interesting section of the work; the allegory of the Thorn Walk, and the Flower Walk (pleasure  seekers) is dull beside it. The importance Diderot attached to these discussions is indicated by this phrase in the preliminary discourse: “If you impose upon me silence about religion and government, I shall have nothing to talk about.” Diderot was still investigating in the Promenade with, on the whole, a further movement from deism towards atheism. There are no Christians in the Chestnut Walk; he refused them the title of philosopher, to him an honourable one.

Diderot gave most attention to the deists and atheists; those were the most formidable protagonists whose philosophy merited the most careful attention. He now used the cosmological argument against the idea of God, putting it this time in the atheists' hands. "If matter is eternal, if motion has so disposed it and originally impressed on it all the different forms which we see that it preserves, what need have I of your prince?" . . . “So long as the structure and organization (économie) of our organs persist, we think; we rave when this changes. When it is destroyed, what becomes of the soul?” The arguments which were opposed to these were of physico‑teleological type, the deists speaking of "universal order," the stars and the hands which must have lighted them.

The atheist answers: "We have before us a vast unknown machine about which observations have been made which prove the regularity of its movements, according to some, and its irregularity and disorder, according to the feeling of others. Ignorant people who have only examined one cogwheel of it, of which they understood hardly a few teeth, make conjectures about their interlocking with a hundred thousand other cogs of which they are ignorant of the motions and actions; and in conclusion, like artisans, they put on the work the name of its author." A worm [25/26] and an ant instal themselves comfortably in a great rubbish heap, made of soil and fragments of stone from a ruined building. What would you think of these insects, if, reasoning your way, they became enraptured with the intelligence of a gardener who had placed all these materials in that way for their convenience".

The deist opposed teleology to causality; not wishing to admit necessity be appealed to liberty. The closer investigation of nature, as with the microscope revealing the structure of the internal organs of a silk‑worm, was put forward as further evidence for the existence of God. "What conclusion could be drawn from the anatomy of the human body and from the knowledge of other natural phenomena?" Nothing, except that matter is organized, was the reply of the atheist. In substance this answer went unrefuted; and the discussion is summed up: perhaps the atheist is right, but probability remains with the deist.

The following phase in Diderot's philosophic development is marked by the Letter on the Blind, for the Use of Those who See (1749). In this the questions discussed covered a wider field than in the previous writings; the theory of knowledge, cosmogony and the philosophy of nature were included in its scope. Diderot showed now that his previous inquiries had allowed him to reach a definite materialism, and the philosophy of his subsequent writings was largely a development of germinal ideas to be found in the Letter on the Blind. Apart from the intrinsic interest of his discussion of blindness in relation to the way in which lack of sight affected the understanding of the surrounding environment, and the ability to think in the abstract, etc. in which field Diderot made interesting original observations, the most important aspect of the Letter is that which develops the philosophical problems.

The fictitious conversation attributed to Saunderson (a famous blind mathematician of Cambridge) allowed Diderot to express his views on the relativity of moral and [26/27] metaphysical notions. The blind cannot understand how such importance is attributed to visual perception. People who can see are moved when they see a suffering animal, yet take no note of the insects they crush underfoot. Some parts of the body may be exposed to view, but not others.

Blind Saunderson, dying, is made to advance the views of the atheist in the Promenade of a Sceptic. He recognizes only what he can feel; to believe in God he must be able to touch him; man can believe in God when he has visible palpable, concrete evidence. Indirect evidence from them beauty and perfection of nature are insufficient; they carry no weight in the face of ugliness and blindness.

The minister of religion who visits Saunderson on his death‑bed, discusses with him the possibility of the existence of God, citing the marvels of nature as evidence for a divine intelligence. Saunderson answers him

"Ah, sir, leave out all about that beautiful spectacle, which was never made for me. I have been condemned to pass my life in darkness; and you cite these prodigies which I do not understand, and which only have weight with you and those who see like you. If you want me to believe in God, you must let me touch him."

The minister directs Saunderson's attention to the divine origin which he should find by manual examination of the admirable mechanism of his own organs, Saunderson answers:

“. . . But if the animal organism is as perfect as you say, and as I should like to believe . . . what has it in common with a sovereign intelligent being? If it amazes you, perhaps that is because you are in the habit of treating as a miracle everything that appears to be beyond your own capacity. I have so often been an object of admiration for you, that I have a poor opinion of what surprises you. I have drawn here from all parts of England people who cannot conceive how I could do geometry; you must agree that these people had no very clear ideas about the possibilities of things. If a phenomenon is in our opinion [27/28] beyond the power of man, we say at once: ‘It is God's handiwork’; our vanity is content with nothing less. Why cannot we put into our discussion a little less pride and a little more philosophy? If nature offers us a difficult knot to unravel, let us leave it for what it is; do not let us introduce, in order to untie it, the hand of a Being who then at once becomes an even more difficult knot to untie than the first one. Ask an Indian why the world stays suspended in space, and he will tell you that it is carried on the back of an elephant . . . and the elephant on a tortoise. And what supports the tortoise? . . . You pity the Indian; and yet it might be said to you, as to him: Mr. Holmes, my friend, confess your ignorance and spare me your elephant and your tortoise.”

The minister falls back upon the authority of Newton, Clarke and Leibnitz, who had been impressed with the marvels of nature and were satisfied with this as evidence for an Intelligent Being as their author. Saunderson replies:

"I see nothing; I admit, however, an admirable order in everything; but I trust you not to expect anything more of me. I grant it you about the present state of the universe, in order to get from you, in return, the liberty of thinking what I like about its ancient and primitive state, about which you are no less blind than I. You have no evidence to oppose me here, your eyes are of no use to you. You may imagine, if you wish, that that order which impressed you has always existed. But leave me free to think it has done no such thing, and that if we went back to the birth of things and of time, and perceived matter in motion and chaos becoming unravelled, we should encounter a multitude of shapeless beings instead of a few highly organized beings. If I have no objections to offer you about the present condition of things, I can at least question you about their past condition. I can ask you, for example, who told you, Leibnitz, Clarke and Newton, that at the first moment of the formation of animals, some were not without heads, others without feet? I can maintain to you, that these had no stomachs, those no intestines; that some to whom a stomach, palate and teeth seemed to promise continued existence, came to an end through some defect of heart or lungs; that monsters annihilated one another in succession; that all the defective (vicieuses) combinations of matter have disappeared, and that there have only survived those in which the organization (méchanisme) did not involve any important contradiction (contradiction),*** and which could subsist by themselves and perpetuate themselves. On [28/29] this hypothesis, if the first man had had a blocked larynx, had lacked suitable food, had had defective organs of generation, had not found a mate, or had propagated with another species, Mr. Holmes, what would have become of our human race? It would have remained enfolded in the general depuration (dépuration) of the universe; and that arrogant being who calls himself man, dissolved and scattered among the molecules of matter, would perhaps have remained for ever among the number of possibilities.

"If there had never been any shapeless creatures, you would not have failed to claim that none will ever appear and that I am plunging into fantastic hypothesis; but the order is not yet so perfect that monstrous productions do not appear from time to time. . . . I conjecture then, that, in the beginning, when matter in fermentation was hatching out the universe, blind creatures like myself were very common. But why should I not believe about worlds what I believe about animals? How many worlds, mutilated and imperfect, were perhaps dispersed, reformed and are dispersing again at every moment in distant space, which I cannot touch and you cannot see, but where motion continues, and will continue, to combine masses of matter until they shall have attained some arrangement in which they can persist. O philosophers, transport yourselves with me to the confines of the universe, beyond where I can touch and where you can see organized beings; move over that new ocean, and seek among its irregular movements some trace of that intelligent Being whose wisdom so astounds you here! But what is the good of taking you out of your element? What is this world? A complex whole subject to revolutions which all indicate a continual tendency to destruction; a swift succession of beings which follow each other, thrust forward and disappear; a transient symmetry; a momentary order. I reproached you just now with estimating the perfection of things by your own capacity; and I might accuse you here of measuring its duration by the length of your own days. You judge the continuous existence of the world as in ephemeral insect might judge your existence. The world is eternal for you, as you are eternal for the being that lives only for an instant; yet the insect is the more reasonable of the two. What prodigious succession of ephemeral generations attests your eternity? What immense tradition? Yet we shall all pass away without being able to assign the real extent we filled in space, nor the precise time that we shall have endured. Time, matter, space are perhaps only a point."

The passage just quoted is one of the earliest of Diderot's great flights of scientific imagination, hinting at a theory [29/30] of biological and cosmological evolution. He returned to the subject again in the Conversation between d'Alembert and Diderot (p. 49), in D'Alembert's Dream (p. 64) and in the Elements of Physiology (p. 134); it always evoked his most eloquent and brilliant efforts.

So much for the earlier development of Diderot's materialism; the subsequent development of his philosophy is contained in the maturer writings which make up the bulk of the present selection.


One aspect of Diderot as a thinker which has never been adequately acknowledged, much less studied, is the fact that within the field of natural science and the philosophy of nature, he was far in advance of his contemporaries in his recognition of the dialectical character of natural phenomena. Outside the field of natural science and of philosophy in the restricted sense, French writers of the Enlightenment produced masterpieces of dialectic. Rousseau's Treatise on the Origin of Inequality among Men, and Diderot's own Rameau's Nephew are high‑water marks of this kind of writing. But Diderot alone was able in some measure to apply the same mode of thinking to the philosophy of nature, or rather, was able to observe this same mode of development in natural phenomena and to apply it in a speculative manner.

It has been usual in the past to class all the French materialists of this period as mechanical materialists, and this is admittedly true of the majority of them. But Diderot is an exception to this generalization; as will be seen, there are many instances, scattered through the writings in this volume, which show him surmounting this limited, mechanical, materialism when he is discussing natural phenomena.

Engels has shown why it was that the working scientists of this period should have been unable to pass beyond [30/31] mechanical materialism. He pointed out that the primitive, naïve view of nature is of "an endless maze of relations and interactions" and that

"this intrinsically correct conception of the world was that of ancient Greek philosophy, and was first clearly formulated by Heraclitus: everything is and also is not, for everything is in flux, is constantly changing, constantly coming into being and constantly passing away. But this conception, correctly as it covers the general character of the picture of phenomena as a whole is yet inadequate to explain the details of which this total picture is composed, and so long as we do nor understand these, we also have no clear idea of the picture as a whole. In order to understand these details, we must detach them from their natural or historical connections, and examine each one separately, as to its nature, its special causes and effects, etc. This is primarily the task of natural science and historical research." (Engels, Anti-Dühring, p. 27. See also p. 335 of this book.)

When real natural science began to develop, in the second half of the fifteenth century, it was first necessary to collect facts, to analyse nature into its individual parts, to group and classify natural objects and their constituent parts, to systematize the accumulating knowledge; it was primarily a collecting science. The only possible way for the laboratory worker to investigate at that stage of development, was to analyse his materials, to discover the elements from which the more complex materials and processes were built up, to isolate portions and to study phenomena piecemeal, and while at rest. This method of study was necessarily imposed by the limitations of the technique that was then available in the laboratories. This static method of investigation, historically inevitable, left as a legacy

“. . . the habit of observing natural objects and natural processes in their isolation, detached from the whole vast interconnection of things; and therefore not in their motion, but in their repose; not as essentially changing, but as fixed constants; not in their life but in their death. And when, as was the case with Bacon and Locke, this way of looking, it things was transferred from natural science to philosophy, it produced the specific limitations of the last [eighteenth—Ed.] century, the [31/32] metaphysical mode of thought.” (Engels. Anti‑Dühring, pp. 27‑8. See the note on p. 336 of this book.) 

This, then, was the background of the French mechanical materialists such as Lamettrie in his Man‑Machine, d'Holbach in the physics section of his System of Nature, Cabanis and others. Along the same lines Büchner, Vogt and Moleschott later developed their mechanical materialism in the nineteenth century. Thus it can be understood that in the investigation of particular limited fields in natural science, there was a two‑fold compulsion to remain mechanical materialists, namely the heritage of the metaphysical mode of thought and the practical limitations of laboratory technique and the stage of development of science. The latter factor necessarily kept practical investigations, especially in the biological fields, at the stage of analysis, of simplification, of dissection. In the historical circumstances, therefore, it was almost inevitable that these French materialists should have been and have remained mechanical materialists.

Diderot, on the other hand, was able to surmount these limitations and that to a surprising degree. In part this may have been because he was not an experimental investigator in a particular field, and was therefore not tied down by the limitations of experimental technique. With his encyclopedic mind, embracing wide fields of science, he was able to survey various special fields, to observe their interconnections, and, viewing natural processes dynamically, to recognize their dialectical character, in contrast to the laboratory workers who had, initially, to isolate and to observe phenomena, not in motion, but at rest. Furthermore, he was a natural dialectic thinker, and was thus able to think in this way when handling scientific material, as well as in the field of social criticism as in Rameau's Nephew.

For these reasons, Diderot was able to take a longer view and to produce the brilliant speculative hypotheses [32/33] which contain in embryo the evolutionary transformist ideas of Lamarcke and Darwin. Diderot criticized the rigidity of the static, arbitrary classifications of the systematists with their “fury” for “modelling existing things after conceptions instead of re‑shaping conceptions to existing things.” This is particularly clearly shown in the Interpretation of Nature (see p. 46). Diderot's criticism is entirely parallel with Engels's remarks that "Nature is the test of dialectics" and that "it is no longer a question anywhere of inventing interconnections out of our brains but of discovering them in the facts."

The most clear‑cut example showing Diderot's distinction from the mechanical materialists is in the section on Animals in the Elements of Physiology (see p. 135), where he remarks: “What idiotic things can be said following this one supposition” that "the animal is a hydraulic machine." He then gives an expansion of his criticism entirely along dialectical materialist lines. An analogous passage from the Dialectics and Nature of Engels is given in the Notes (see p. 349, section V, note 4).

Other examples of dialectic thinking and the recognition of dialectic processes in nature abound in the Conversation between d'Alembert and Diderot and D'Alembert's Dream to which references are made in the Notes. Similarly there is the passage in the Supplement to Bougainville's "Voyage," on the mutability of human vows in the face of a constantly changing nature.

Diderot's recognition of the dialectical character of natural phenomena is derived from the naïve dialectics of the early Greek philosophers; it is not a conscious analysis of the forms of dialectic development. This was to come, and fourteen years before Diderot's death the man had already been born—namely Hegel—who was to develop conscious dialectics in its widest and most general form, although upon an idealist basis. But for Diderot the recognition of the dialectics of nature was that of a scientist on whom the [33/34] facts of science, the facts of life itself, thrust themselves, making evident the dialectical character of natural events to a mind not rendered unreceptive by the heritage of a metaphysical philosophy, but avid to receive it.

Diderot is the outstanding example for his epoch of this process by which natural science is forced to recognize the dialectical character of nature, a process which Engels has described for the natural science of his own time in the preface to Anti‑Dühring. Not until the work of Marx and Engels was conscious dialectics applied to the materialist conception of nature and history. Only since their work has consciously dialectical natural science been possible. Diderot marks the transitional stage in the development of natural science towards the conscious recognition of the dialectic of nature. He is the first materialist who began to burst through the restrictions of mechanical, metaphysical materialism.

J. K.

* Letter on the Publishing Trade, "Oeuvres Complètes'' XVIII, 16.

** State permission for publication, subject to conditions.

*** See Elements of Physiology, p. 134.

SOURCE: Diderot, Denis. Diderot, Interpreter of Nature: Selected Writings, translated by Jean Stewart and Jonathan Kemp, edited and with an introduction by Jonathan Kemp. 2nd ed. New York: International Publishers, 1963. viii, 358 pp. (1st ed. 1937) Introduction, pp. 1-34.

Note: Footnotes have been reformatted into endnotes.

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