Denis Diderot

Denis Diderot was a French philosopher and writer who, as chief editor of the Encyclopédie, directed the most ambitious publishing project of the Enlightenment. Over some twenty-five years, against censorship, bans and the defection of collaborators, he brought out a vast reference work that set out the knowledge of the age in a critical, secular spirit. He was also a materialist philosopher, a playwright, a pioneering art critic and the author of experimental fiction, though many of his boldest works were published only after his death.

Diderot was born on 5 October 1713 in Langres, in Champagne, in eastern France, the son of a prosperous master cutler. He was educated by the Jesuits in Langres and was intended for the church, receiving the tonsure at thirteen. He went on to study in Paris, taking a master of arts degree from the University of Paris in 1732, but then refused to settle into the law or any other profession. His father cut off his allowance, and for about a decade he lived a precarious life as a tutor, hack writer and translator. In 1743 he married Antoinette Champion, a linen seamstress, against his father's wishes; of their children only a daughter, Angélique, survived to adulthood. In the 1740s he also became close friends with Jean-Jacques Rousseau, whom he met over chess and coffee.

Diderot's translations included Lord Shaftesbury's Inquiry concerning Virtue and Merit (1745). His own first original book, the Philosophical Thoughts (1746), defended natural religion against both superstition and atheism but was burned by order of the Parlement of Paris. Over the next few years he moved towards materialism, the view that everything, including thought, can be explained by matter in motion. In the Letter on the Blind (1749) he imagined the English mathematician Nicholas Saunderson, blind from infancy, on his deathbed rejecting the argument that the order of nature proves the existence of God, since he had never been able to see that order. The book suggested that our moral and religious ideas depend on our senses, and it led to Diderot's arrest. He was held in the fortress of Vincennes from July to November 1749, and released only after promising not to publish anything more of the kind.

The project began modestly in 1745 as a French translation of Ephraim Chambers's Cyclopaedia, an English encyclopaedia, for the bookseller André Le Breton. In 1747 Diderot and the mathematician Jean le Rond d'Alembert became its editors, and they turned it into something far larger: an Encyclopédie, or Reasoned Dictionary of the Sciences, Arts and Trades. Its aim, in Diderot's words, was to change the common way of thinking. The first volume appeared in 1751, with a preliminary discourse by d'Alembert that traced all knowledge to memory, reason and imagination, following the scheme of Francis Bacon.

Contributors included Voltaire, Montesquieu, Rousseau, the economist François Quesnay and the tireless Louis de Jaucourt, who wrote around a quarter of the articles. The Encyclopédie gave unusual attention to the mechanical arts, describing crafts and industries in detail and illustrating them with hundreds of engraved plates, a sign of respect for practical work. Its criticism of religion and authority was usually indirect, slipped into unexpected articles or signalled by cross-references, but it was unmistakable. The authorities suspended it in 1752, and after the scandal over Helvétius's materialist book De l'esprit in 1758, the royal privilege was revoked in 1759 and the pope condemned the work. D'Alembert withdrew, leaving Diderot to carry on largely alone. The remaining ten volumes of text were prepared in semi-secrecy and issued together in 1765 with a false imprint, and the last of eleven volumes of plates appeared in 1772. Diderot was furious to discover that Le Breton had secretly cut passages from the final volumes for fear of prosecution. In all, the work comprised seventeen volumes of text with some 72,000 articles, thousands of them written by Diderot himself.

Diderot never wrote a philosophical system, preferring dialogues, letters, stories and essays. His mature views, set out most fully in D'Alembert's Dream (written 1769), were those of a thoroughgoing materialist and atheist: matter is capable of sensation, living things develop and change over immense periods, and the self is a temporary organisation of matter. These ideas anticipated later theories of evolution in some respects, though they were speculative rather than scientific. In ethics he sought a morality grounded in human nature and happiness rather than religious command.

His fiction was equally inventive. The Nun, based on a real case, attacked forced religious vocations. Rameau's Nephew, a dialogue with a brilliant, cynical parasite, explores the conflict between morality and self-interest, genius and society; it reached print in a German translation by Goethe in 1805, and Hegel and Karl Marx admired it. Jacques the Fatalist toys with the reader in the manner of Laurence Sterne's Tristram Shandy while raising questions about free will. He also wrote plays promoting a new middle-class domestic drama, and the Paradox of the Actor, which argued that great actors keep cool heads rather than feeling the emotions they portray. From 1759 he reviewed the biennial Paris art exhibitions, the Salons, for Friedrich Melchior Grimm's private newsletter to European courts; these reviews are often considered the beginning of modern art criticism.

Diderot never grew rich from the Encyclopédie. In the mid-1760s Catherine the Great of Russia, hearing that he planned to sell his library to provide a dowry for his daughter, bought it on condition that he keep it for life and paid him a salary as its librarian. In 1773–1774 he travelled to Saint Petersburg to thank her, spending several months in long conversations with the empress, but he was disappointed that she showed little interest in putting his reform proposals into practice. In his last years he contributed anonymously some of the most radical passages, denouncing colonial conquest and the slave trade, to the abbé Raynal's History of the Two Indies. He died in Paris on 31 July 1784 and was buried in the church of Saint-Roch.

The Encyclopédie became a symbol of the Enlightenment and of the confidence that knowledge freely shared could improve society, and it was later seen as an intellectual forerunner of the French Revolution. Because his most daring writings circulated only in manuscript or appeared after his death, Diderot's reputation grew slowly through the nineteenth and twentieth centuries, and he is now regarded as one of the most original minds of his century.