Denis Diderot

Diderot, Denis (1713–84)

Chief editor of the great eighteenth-century Encyclopédie (1751–72), Diderot set out a philosophy of the arts and sciences which took the progress of civilization to be a measure of mankind’s moral improvement. He did not regard that progress as having produced universal benefits, however, and perceived the Christian religion which had accompanied it as morally harmful to those who subscribed to it and even more dangerous to societies thus far untouched by it. Religious dogmas tended to pervert the organic development of human passions, and secular education which presumed that all minds were equally receptive to instruction threatened to thwart the natural evolution of human faculties in other ways.

Like Rousseau, Diderot subscribed to a philosophy of education which encouraged curiosity rather than promoted truth. He stressed the need for the adaptability of moral rules to the physiological characteristics of the individuals to whom they applied, pointing to a connection between human cultures and biology in a manner that would influence fresh outlooks upon the sciences of man at the end of the Age of Enlightenment.

1 Encyclopedic polymath

One of the most central figures of the European Enlightenment, Diderot was chiefly renowned in his own lifetime as the principal editor of the Encyclopédie (1751–72), constructed as a monument of human reason and invention, like the Crystal Palace that would be built in London a century later in celebration of an age of industry and commerce. More than any other philosopher of the eighteenth century, he shaped his intellectual career around the production and circulation of books, which in progressive circles were held to be both the vehicle and measure of enlightenment for an epoch of greater literacy and prosperity than Europe had ever known before.

Appointed with Jean Le Rond D’Alembert as joint editor of the Encyclopédie in 1747, Diderot initially undertook to write more articles himself than any other contributor to this reasoned dictionary of the arts and sciences, whose publishing history from 1751 would eventually extend over a period of thirty years, and whose thirty-five volumes would come to embrace 20 million words and more than 2,000 plates. As the guiding spirit of that collective enterprise of men of letters, Diderot often reassembled the ideas of other thinkers, drawing upon ancient and modern sources alike, from Lucretius to Shaftesbury. Having begun his literary career around 1743 as a translator, he proved the Enlightenment’s most expert literary ventriloquist, sometimes passing off borrowed material as if he had written it himself, sometimes ascribing his own ideas to others.

In part because so much of his best work was to appear posthumously, often in the form of fictional dialogues, Diderot came to be regarded as the Enlightenment’s most eclectic thinker, displaying a special fondness for the pluralist dimensions of eclecticism in general in his own entry on that very subject for the Encyclopédie, itself indebted to other authors. In Le Neveu de Rameau (Rameau’s Nephew) (1762–74) in particular, deemed by Hegel, Goethe and Marx to be the finest work of the whole Enlightenment, he portrays the character of the most explosively original and romantic personality of eighteenth-century European literature as at odds with itself and also with Diderot, who figures both as the author of the dialogue and a personage within it, depicted as conventional in upholding a bourgeois code of morals. As distinct from some of his equally celebrated contemporaries – such as Montesquieu, Voltaire or Rousseau – Diderot elaborated no single overriding doctrine, nor did he devote himself to one great intellectual crusade.

Especially well versed in the history of philosophy, he extolled its ancient and modern achievements alike, from Epicurean doctrines of continual flux, to Spinozistic conceptions of selfsufficiency, to the atheistic materialism of La Mettrie and Maupertuis. In his Pensées philosophiques (Philosophical Thoughts) of 1746, largely inspired by Shaftesbury, he put forward a set of aphorisms that expressed notions of natural law and ideals of natural religion, which could be engraved in the human heart without need of Christian scruples. In his Lettre sur les aveugles (Letter on the Blind) of 1749, he set out a case for the adaptability of the senses as evidenced by the fact that mental images could be formed without sight or conversations pursued without sound, believing that powers of perception were transitive across human faculties and did not themselves spring from sensory experience. The late eighteenth-century teaching of sign languages to the deaf, and the deep structural grammars of modern Chomskian linguistics, were to draw inspiration from such claims that fundamental human capacities are not determined by the contingencies of their exercise. At the time of its publication, however, Diderot’s Lettre sur les aveugles only managed to invite the suspicion that he was a materialist and atheist, on which grounds he was to be imprisoned in Vincennes for over three months.

In the longest of the contributions to the work of which he was chief editor, the article ’encylopédie’ itself, he expounded themes of practical or applied philosophy that could bring the arts and sciences of civilization together, by encouraging the interpenetration of the liberal with the mechanical arts and the cooperation of specialists across disciplines, along lines that bridged what we have come to term ‘the two cultures’. In showing how science had been rendered useful to the public interest or common good through such inventions as the compass and the printing press, Diderot sought to provide tangible illustrations of a Platonic ideal of promoting virtue through knowledge. His goal, like that of so many other philosophes of the eighteenth century, was to cast off the veil of ignorance and lift the yoke of precedence, thus overcoming dead dogma. Almost as much as D’Alembert’s preliminary discourse to the Encyclopédie , Diderot’s own article on that very subject could be read as a general manifesto of the Enlightenment.

2 Speculating about politics

His political philosophy was first propounded in the Encyclopédie, particularly in articles such as autorité politique, which offers a theory of the social compact that binds both the prince and his subjects to one another without recourse to theological sanctions; and droit naturel (natural law), which sets out a theory of universal justice with respect to mankind’s ‘general will’, a term of scant significance in the history of political thought before Diderot gave it fresh impetus. In 1774, in his Observations sur le Nakaz , or commentary on a new code of law for Russia as proposed by the empress Catherine the Great, he called for a programme of secular education to stimulate the civilization and selfreliance of that country through indigenous and small-scale enterprises, opposing the importation of Western physiocratic doctrines and their schemes of wholesale agrarian reform within a cultural environment to which they were ill-suited. Catherine had purchased Diderot’s library and had invited him to St Petersburg, but she failed to convince him of the wisdom of her efforts to reform the political system of her nation along lines she imagined had already been achieved in the West. While advocating the emancipation of serfs, which was not to her liking, Diderot was convinced that material progress in Russia should proceed apace with its intellectual development rather than in accordance with alien precepts of modernity.

As editorial spokesman for the cause of enlightenment and a major contributor on political subjects to the Encyclopédie, Diderot stood for principles which appear to differ sharply from those of Rousseau, for fifteen years his closest companion, who had conceived the central idea of his own philosophy of history – which forms a moral critique of the progress of the arts and sciences – en route to visit his friend in prison. Whereas Rousseau decried the moral consequences of the progress of the arts and sciences, Diderot applauded them. Whereas Rousseau subscribed to ideals of spartan republicanism, Diderot was cosmopolitan and willing to encourage monarchical regimes so long as their authority was tolerant and benign, directed to the promotion of the public interest. Rousseau’s notion of the general will, as an ideal of public engagement only conceivable to the citizens of selfgoverning states, was largely designed to contradict Diderot’s conception of the same term as pertaining to the common humanity of individuals even when motivated by self-interest, in so far our notions of what is right and good do not, Diderot supposed, depend upon our political identities.

If, for Rousseau, men’s morals were shaped by their politics, Diderot was instead convinced that politics were fundamentally shaped by morality. In his article hobbisme for the Encyclopédie, he contrasted Rousseau’s idea that society rendered mankind malicious with a Hobbesian notion that war was our species’ natural state, rejecting them both (see Hobbes, T.). Believing that conflict was not inescapable either in nature or in society, he upheld an alternative doctrine, which he drew ultimately from Pufendorf’s De iure naturae et gentium (1672), that human frailties had rendered civil society necessary, while the natural sociability of selfishly motivated persons had rendered it possible and, at least in principle, beneficial as well (see Pufendorf, S. ).

3 On primitivism, religion and sexuality

In his Supplément au Voyage de Bougainville (Supplement to the Bougainville Journey) , dating from the early 1770s but largely unpublished until after his death, Diderot was to portray the virtues of a primitive society in colours so attractive as to seem to shed doubt upon his allegiance to the moral splendours of civilization. This text, purporting to serve as an appendix to one of the earliest descriptions of Tahiti, contrasts an exotic world characterized by the zealous satisfaction of bodily appetites with a familiar world wherein it is dictated that they should be repressed. Diderot’s depiction of a society in which sexuality is celebrated, and within which incest, adultery and fornication are not held to be either criminal or sinful, forms a critique of monogamy, celibacy and sexual repression in the West at the same time as it offers tribute to the promiscuity of Polynesians.

The Supplément’s fictional opposition of two cultures – one stirred naturally by libidinous desire, the other artificially held in check by religion and hypocrisy – owes a debt to the Lettres persanes (The Persian Letters) (1721) of Montesquieu and more generally to eighteenth-century travellers’ tales, either real or imaginary, which found European, and most particularly Christian, civilization to be at fault in the light of Oriental alternatives. In granting tangible presence and geographical specificity in the modern world to a population that still enjoyed the freedom of its state of nature, Diderot also seems to have drawn inspiration from Rousseau’s Discours sur l’inégalité (Discourse on the Origin of Inequality) (1755). Like Rousseau, he judged that the moral values which prevailed in the West were often contrary to human nature, which they distorted through artifice, subterfuge and selfdeception.

Especially with respect to the sexual longings of individuals in Christian communities, and above all the warped personalities of their monastic priests, Diderot was convinced that in Western cultures there had arisen a great gulf between human physicality and morality. But he did not share Rousseau’s view that such a gulf was unbridgeable. He imagined that Tahitian society showed how it could be overcome, in promoting the public interest out of individuals’ sexual proclivities, thereby stimulating a socially welcome growth in population. The irreverent, sensuous, liberal, anti- colonial and utilitarian themes of the Supplément au Voyage de Bougainville pursue, in different idioms, a philosophy which springs from the same point of view that informed Diderot’s contributions to the Encyclopédie and to which he was to subscribe virtually all his life – the belief that great public benefits may spring from unconstrained selfish sociability. In holding to such a doctrine, more often associated in diverse formulations with Bernard Mandeville and Adam Smith , Diderot espoused one of the most central moral philosophies of the whole Enlightenment.

4 Theory of education

At least some of the tensions which are manifest in his writings reflect the clash of principles and personalities that he perceived in the world at large. At once a materialist and an atheist, Diderot was determined to describe the behaviour of individuals empirically, in all their diverse, contrasting and irregular forms. Such diversity and contrast were features of human nature as much as of human history, he supposed and, in his Réfutation de l’ouvrage d’Helvétius intitulé ’L’Homme’ (Refutation of Helvétius’ Work Man) of 1774, he accordingly took issue with the famous dictum of Helvétius’ De l’homme, published posthumously in 1773, that ’ l’éducation peut tout’ (see Helvétius, C.-A. ). The proposition that education can achieve everything was false, according to Diderot, because it presumed that men and women were everywhere identical and that differences in character depended entirely upon the circumstances of a person’s upbringing.

Because this supposition appealed to a notion of human equality, it was tempting to believe, in the light of it, that all individuals at birth shared the same capacities. But that was a delusion, Diderot contended, based on the false premise that each person was motivated only by his or her sensations which, through instruction and refinement, would become the grounds of every sort of rational and moral judgment. It was impossible, Diderot insisted, to pass directly from sensation to judgment or, in effect, from animal reflexes to human design. Intraspecifically, it had to be noted that only humans possess the capacity to reason and thus to formulate ideas and combine them into judgments. Interspecifically, it was necessary to remark that individuals exhibit their reason in different degrees, mental capacity as a whole being unequally distributed. In allowing with Helvétius that vices do not spring from human nature but are generally attributable to harmful social practices and teachings, there should be no presumption that all individuals have good minds, endowed with a latent natural genius just awaiting cultivation and training.

Diderot’s critique of the philosophy of education of Helvétius bears a striking resemblance to Rousseau’s challenge, made in Émile a decade earlier, of much the same theory of the formation of the human intellect and character already sketched in Helvétius’ De l’esprit (1758). Rousseau and Diderot were each convinced that genius cannot be instilled by tuition and that education ought to nourish the natural dispositions and qualities of children rather than impose their tutors’ designs and expectations upon them. Their common objections to Helvétius nevertheless took different forms. While Rousseau decried materialism in general, Diderot took issue only with that crude variant which, on his understanding, reduced all thought to pure sensation. Whereas Rousseau mistrusted teachers who either believed or pretended that they spoke on God’s behalf, Diderot was persuaded that God himself had been invented by man. He judged that Rousseau had fundamentally confused unsociability for selfreliance, and he showed no interest in promoting any scheme of negative education that might be fit for children freed from all dependence on others, like Robinson Crusoe learning to fend for himself.

Diderot’s conception of human nature differs from Rousseau’s in attributing more dynamic potentialities for change and self-improvement to each individual’s seminal personality. If he had coined the term perfectibilité, which was in fact invented by Rousseau, it would have encapsulated his understanding of the spark of genius, the impulse of creativity and the moral formation of character. Yet both men agreed, in contrast with Helvétius, that education ought fundamentally to accord with human nature instead of recasting it. Each subscribed essentially to a belief in self-education, aiming to encourage children to follow their intuitions and thereby attain intellectual and moral maturity by being true to themseves. They also shared a profound mistrust of the superstitious idolatry that passed for a Christian education, proffered in priestly interpretations of the mysteries of Holy Writ. As opposed to the arcane dogmas of a revealed religion, they were drawn to the spectacle of creation and to the open book of nature. They both thought that education ought to be pursued endogenously, out of natural curiosity, accompanying the development of the human faculties, and never by indoctrination.

5 Vitalist materialism

It is hardly surprising that a philosopher who advocated that moral principles should be true to Nature, which he believed to be in a state of continual flux, should have found himself suspected of lack of consistency. Like his colleague and co-editor of the Encyclopédie, D’Alembert, he saw his own Age of Enlightenment as committed to a systematic spirit but not the spirit of system which had distinguished the principal contributions of seventeenth-century European philosophy. Although he was the author of a treatise on mathematics and geometry, he was more interested in matters of style, particularly with respect to painting, music and the theatre. His Salons (1759– 81) comprise perhaps the principal contribution to art criticism in the eighteenth century, and his posthumously published Essai sur la peinture (Essay on Painting) ( written in 1765) was to stir the imagination of Baudelaire and other admirers in the Age of Romanticism.

He is better described as an empiricist than as a rationalist, indebted more to the philosophical methods of Bacon and Locke than to those of Descartes and Leibniz. He was a materialist in denying the existence in man of an intangible spirit or soul, and over the course of his life he became a progressively more outspoken atheist, in rejecting all notions of either a transcendent or immanent God. As is most conspicuous from his so-called Lettre à Landois (1756) and his novella Jacques le fataliste (written in 1773) he was at once a philosophical determinist, convinced that Nature left no room for unpredictability or caprice, and at the same time a libertarian, who identified the fundamental dignity of human conduct in terms of autonomous agency and choice, in poignant recognition of the bittersweet paradox that to choose is to act from a motive beyond one’s control.

Diderot’s materialism drew more inspiration from the sciences of physiology and medicine of his day than from physics, since he perceived matter not as inert but as inherently active and self-animating, as a collecton of atoms in a seminal fluid in continual fermentation. He was struck by Haller’s research on the sensitivity and irritability of organic matter and was most particularly impressed by Bordeu and the Montpellier School of physiological medicine, which excited his interest in the internal mechanisms that gave impetus to such matter and regulated its health. Like Montesquieu, he sought to investigate the dynamic forces and tensions which shape the conduct of both living bodies and social systems. To the extent that a number of human sciences would around the end of the eighteenth century come to address such issues as apparently more fundamental than the constitutional and legislative programmes of Enlightenment political theorists, Diderot may be regarded as a philosophical precursor of such change.

Michel Foucault’s depiction in Les mots et les choses: une archéologie des sciences humaines (The Order of Things) (1966) of certain epistemic metamorphoses within the sciences of man that may be dated from around 1770 to 1800 could have embraced the materialist philosophy of Diderot in addition to the examples offered from economics, linguistics and biology (see Foucault, M. ). Diderot’s reflections on the organic forms and forces of social life and on the growth and decadence of civilizations might in the twentieth century have come to be termed ‘structural-functionalism’. In his own day they illustrate an approach to the science of society which would progressively displace speculations about the moral dimensions of human conduct with investigations into its underlying, bodily or material, causes. They herald the advent of ‘sociology’ in the nineteenth century in so far as it was modelled upon eighteenth-century ‘physiology’.

6 Central tenets in oblique articulations

Diderot’s reflections on the arts, human nature and society were not only to strike his readers among romanticists and scientists alike as particularly modern. By virtue of his irregular and sometimes fitful literary style, his preference for the cut and thrust of the dialogue over the discursive finality of the treatise, and his pursuit of anonymity as the mysteriously unidentified author of his own texts, he anticipated some of the philosophical issues raised by postmodernist thinkers today, often in criticism of the so- called ‘Enlightenment Project’ as a whole. No major writer of the eighteenth century left so many of his principal works unpublished in his lifetime, even though several, including the best among them, had been drafted long before his death. No encyclopedist ever managed better to convey his own thoughts by way of plagiarism, insinuation, multiple cross-references and deliberately misleading notes and commentaries. In assuming the personae of historical figures whose ideas he transcribed in his own fashion, and of characters he invented in order to contradict himself, he succeeded more than any other eighteenth-century writer in bestowing independent life upon his work, in the act of creation releasing it from the pen of its author. Like Socrates in Plato’s Phaedrus or Derrida in De la grammatologie , he sought to ensure that the dead hand of script would not count as his last word. Even through his writings Diderot’s voice appears to speak aloud, weaving a conversation without end.

If coming to final conclusions was not his chief aim either as a philosopher or as an encyclopedist, a number of unsettled doctrines may nevertheless be ascribed to him as among his most significant contributions to eighteenth-century thought across several disciplines. First, he supposed that civilizations were like socially organic forms of life, marked by cyclical patterns of growth, maturity and decay, and by institutions which reflected the dynamic or repressive character of their moral or religious principles (see Toynbee, A.J.). In these beliefs, which above all inform his contributions, dealing with global history, to Abbé Raynal’s Histoire des Deux Indes (History of Two Indias) (1772–80), he was guided both by Buffon’s Histoire naturelle (Natural History) (1749–88) and by Montesquieu’s Esprit des lois (The Spirit of the Laws) (1748) (see Buffon, G.L.L.; Montesquieu, C.L. de Secondat).

Second, he held that biological attributes of human nature – including instincts for survival and companionship but also bodily weaknesses and mental stupidity endemic to solitary existence – made society both necessary and possible. His Apologie de l’abbé de Prades, together with several of his articles on political subjects for the Encyclopédie , make plain the influence upon him with respect to this subject of Pufendorf, as well as the double-edged nature of his rejection of Hobbes’s and Rousseau’s differing perspectives on mankind’s isolated state of nature.

Third, he was convinced that moral rules which dictate human conduct could promote the general interest of a society only if they accorded with and gave free rein to the physical desires of its members. Both in Le Rêve de d’Alembert (1769) and the Supplément au Voyage de Bougainville , he put a case for the ultimate physicality of human nature, whose constituent matter he believed to be moved by vital forces which would ensure its natural development towards an appropriate morality unchecked by extraneous rules. Convinced that liberty and necessity went hand in hand, he saw certain features of Western civilization as injurious to freedom when they attempted to obstruct the determinate mechanisms of natural law, as was the case most particularly with religions whose codes of duty stifled the expression of usefully pleasurable passions, thereby harming both individual wellbeing and public peace. In the light of his philosophy, he would have emblazoned our churches and their attendant institutions with warnings of the hazards they pose to our health. He thought Christianity was not only the opiate of the people but a spiritually carcinogenic poison.

Fourth, he believed that political and social institutions needed to correspond as well to a population’s national or regional temperament and to its level of development. Just as punishments would be tailored to crimes, so laws should fit the communities they serve and direct. In his Observations sur le Nakaz he claimed that the character of the Russian peasantry was ill-suited to the drastic reforms proposed by French physiocrats, while in the Histoire des Deux Indes he argued that the fresh freedoms won in America were unlikely to take root in the acidic old soil of Europe. If he would not categorically exclude a favourable meaning for the term ‘enlightened despotism’, Diderot believed that good government was never harsh and that no people ought to be governed too much.

All of these principles of organic growth and adapatibility led Diderot to perceive human liberty in much the same way that Montesquieu described laws – that is, as a set of necessary relations deriving from the nature of things. The character of individuals must not be forced, he thought, but, in passing gradually and without impediment through the seasonal changes of their constitutions, whole populations naturally change themselves. As their nature changes, so too should their political systems. The metamorphoses of human development ought only to record the various stages of our species’ spontaneous generation.