Denis Diderot: Philosopher, Novelist, and Editor of the Encyclopédie

The most remarkable thing about Diderot’s life is that he was, by his own confession, nobody in particular. He was a provincial cutler’s son, a failed law student, a hack writer of sermons and translations, the lover of a woman of letters for whom he had little respect, the father of a child he rarely saw, and the author of at least three of the most original works of the eighteenth century that he did not bother to publish. Le Neveu de Rameau — Rameau’s Nephew — the dialogue that Goethe translated in 1805 and that has since been called the greatest piece of French prose of the century, lay in manuscript from the 1770s until 1823. Jacques le fataliste waited longer. Le Rêve de d’Alembert circulated privately and was not printed in full until 1830. Meanwhile Diderot’s Encyclopédie — the project that made him internationally famous, the work of twenty-five years and seventy-one volumes — was, by his own private estimate, only a third as important as the Encyclopédie he had wanted to write.

He was, in short, the kind of writer posterity has to dig out, and the fact that we have done so is one of the more interesting facts about French intellectual history.

A Provincial’s Progress

Diderot was born on October 5, 1713, in Langres, a small city in Champagne, the eldest surviving son of a master cutler. His father, Didier Diderot, was the kind of man who expected his sons to take up respectable trades. The young Diderot was educated first at the Collège de Juilly, a Jansenist school near Paris, where he picked up enough Latin to read Lucretius, and then at the Collège d’Harcourt, where he picked up little of value. His father wanted him to study law. He studied it, disliked it, and eventually abandoned it. His father, in the immortal opening of Diderot’s own Lettre à mon frère, “did not say much, but the look he gave me was eloquent.”

For the next decade, between roughly 1732 and 1744, Diderot lived the hand-to-mouth life of a Grub Street intellectual in Paris. He wrote sermons for cash. He translated Robert James’s Medicinal Dictionary — a vast undertaking that he never finished, though he used it to teach himself medicine, biology, and the natural philosophy of his contemporaries. He took rooms in a house on the rue Taranne, where he lived with Antoinette Champion, known as Madame de Puisieux, a woman of letters who bore him a daughter in 1743 and about whom he wrote, in Les Bijoux indiscrets, the most damaging portrait of a mistress that any French writer had yet committed to print.

The arrest came in the summer of 1749. La Lettre sur les aveugles à l’usage de ceux qui voient — Letter on the Blind, for the Use of Those Who Can See — was a deceptively modest work of natural philosophy. In it, Diderot reconstructed, as a thought experiment, what a person born blind would make of the proofs for God’s existence from the design of the visible world. The argument’s conclusion — that a blind man, lacking the very experience of light on which the design argument depends, would have no reason to accept it — was, in the religious climate of 1749, an act of intellectual arson. Diderot was arrested at his lodgings on the rue de l’Échelle, held for three months at the Château de Vincennes, and released in November. The episode is worth pausing on. Letter on the Blind was a best-seller, sold freely in Paris, and was widely read. The regime did not arrest Diderot for being wrong about God. It arrested him for being public about being wrong about God, and for having the bad taste to suggest that Samuel Réaumur, the powerful secretary of the Académie des Sciences, was the model for one of his fictional characters.

The Encyclopédie

The commission that changed Diderot’s life came in 1745. André Le Breton, a successful Parisian publisher, had secured the rights to translate into French the Cyclopaedia of Ephraim Chambers, the English universal dictionary. The project was to be a straightforward translation. Le Breton hired Diderot to oversee it. Within a year, Diderot had persuaded Le Breton, d’Alembert (whom he recruited as mathematics editor in 1746), and the other backers to abandon the translation model entirely and to attempt a new work that would do for France what Chambers had done for England and more. The first volume appeared in 1751. The last of the original seventeen volumes of text appeared in 1765, with eleven volumes of plates following in 1772. The full work contains about 70,000 articles by approximately 140 named contributors, of whom the most active were Diderot himself, who wrote nearly 6,000 articles (a number that has been revised upward by recent bibliometric work), d’Alembert for mathematics, Rousseau for music, and Louis de Jaucourt, a working physician, who contributed roughly 18,000 articles on natural history, law, and politics.

The scholarship on what the Encyclopédie actually was has changed substantially in the last forty years. The older Anglo-American view — Robert Darnton’s famous account of the Encyclopédie as a kind of secular scripture for the revolutionary bourgeoisie — has been complicated, though not destroyed, by the careful work of the Inventaire project at Berkeley, of Jean-Marie Goulemot at Paris-VII, and most recently by Andrew Curran in Diderot and the Art of Thinking Freely (2019). The more we know about the actual readership — a tiny, mostly noble, mostly clerical group of perhaps 4,000 subscribers — the harder it is to read the Encyclopédie as the manifesto of a rising class. The Encyclopédie was, in fact, a more cautious work than its reputation suggests. Diderot and d’Alembert kept the radical articles (the famous entries on “Authority,” “Political Authority,” and “Intolerance”) interspersed with conventional, even reactionary, contributions from the Jesuit and Jansenist authors they also employed. The genius of the project was less its uniformity of doctrine than its peculiar mode of cross-referencing: a reader who looked up “Intolerance” was guided, by a system of asterisks and see-also references, to articles that undermined the entry’s own surface claim.

The publication history is one long pitched battle. The privilège was withdrawn in 1759, and from that year to 1765 the Encyclopédie was an officially banned book. Diderot got it finished anyway, with a fake Amsterdam imprint and a series of bribes to the lieutenant of police. The work had to be smuggled back into France for sale, and Diderot was once almost arrested for it on the Pont-Neuf. The personal risk he ran was, in the end, less than he liked to suggest. The police had standing orders not to confiscate the work; the regime’s calculation, which proved correct, was that the Encyclopédie’s mostly noble subscribers were not the kind of people one bothered.

The Philosophy

Diderot’s mature philosophy is concentrated in three short dialogues written in the 1760s and 1770s — L’Entretien entre d’Alembert et Diderot (1769), Le Rêve de d’Alembert (1769), and Suite de l’Entretien (written c. 1772 but unpublished in Diderot’s lifetime). The system is a hard materialism with a fascinating twist. The world, in Diderot’s account, is composed of a single matter in motion. The properties of bodies — color, weight, elasticity, even, eventually, thought — are all functions of the arrangements of this matter. The standard objections to materialism (the irreducibility of consciousness, the apparent discontinuity between mind and body) Diderot answers by appeal to a speculative biology he had absorbed from Maupertuis, Buffon, and the Lettres philosophiques of Bonnet: matter, given the right kind of complexity, can think, and once it does, the question of “how” is no more mysterious than the question of how a fluid can be solid. The matter of thought is the same matter as the matter of the body, in a different arrangement.

The argument is bolder than anything in Voltaire, more careful than anything in La Mettrie, and more self-consciously tentative than anything in d’Holbach. Diderot’s habit, in the Rêve, of having his characters say things and then immediately qualify them — “tout est lié, sans doute” — is the mark of a thinker who took the experimental method seriously. He is not interested in the conclusion that everything is connected. He is interested in showing the reader how the experimental mind arrives at the conclusion, and at what points the conclusion is reasonable but not certain.

It is the most underrated work of philosophy in the French Enlightenment. Recent scholarship — particularly the work of François Pépin and the late Colas Duflo — has done a great deal to rehabilitate it from the long condescension of the nineteenth century, which treated Diderot as a clever journalist who occasionally wrote decent philosophy.

The Late Fiction

Diderot’s two great novels, Le Neveu de Rameau and Jacques le fataliste, are the works in which his philosophy becomes most fully visible. The “I” of Le Neveu is not quite Diderot, the “He” is not quite Rameau’s nephew (the actual nephew, a real musician named Jean-François Rameau, was in fact a more respectable figure than the dialogue suggests), and the dialogue is not quite a dialogue. What it is, in the most general sense, is the central moral problem of the modern age put into conversation: can a man who has sold his talent live a good life, and what is the difference, if any, between a “use” of vice that is also a critique of it? The nephew is contemptible and also the most honest observer in the room. The philosopher is right and also a kind of fool. The dialogue’s form is itself the answer.

Jacques le fataliste is a more ambitious experiment. Its narrator is a kind of incompetent deity who keeps trying to push the story toward moral lessons and is constantly interrupted by Jacques, who has decided that human actions are determined and that the search for moral instruction in them is comical. The novel reads like a parody of Tristram Shandy written by a man who had absorbed Tristram Shandy and decided to outflank it. There is nothing else like it in eighteenth-century French.

The Russian Affair

The visit to Saint Petersburg in 1773–1774, at the invitation of Catherine the Great, has been a source of embarrassment to French writers since 1860. Catherine bought Diderot’s library — at Diderot’s own absurdly high asking price, paid in cash — and appointed him librarian, with a salary of 1,000 roubles a year, on the condition that he come to Russia and tutor her personally in the art of being an enlightened monarch. Diderot accepted, and spent five months in the Hermitage, where he composed his Observations sur le Nakaz, a long and devastating marginal commentary on Catherine’s Instruction to the legislative commission. The Nakaz itself was, in Catherine’s hands, a clever piece of absolutist flattery to European opinion; the Observations are the work of a man who was flattered to be flattered and yet could not help noticing that he was being used.

The Diderot–Catherine exchange is one of the great instructive moments of Enlightenment history. It is worth reading alongside Voltaire’s correspondence with Frederick the Great and the French philosophes’ long correspondence with Gustavus III of Sweden. The pattern is consistent: the philosopher believes he is using the prince; the prince is, in fact, using the philosopher; and both end up producing texts that are more cynical and more politically acute than either would have written alone.

A Judgement

Diderot is, with the partial exception of Voltaire, the only French Enlightenment writer who has steadily gained stature in the seventy years since his bicentenary. The reasons are several. He is a better prose writer than Voltaire, in the same sense that Haydn is a better composer than Handel — more inventive, less showy, with a surer sense of where the line should fall. He is a more rigorous philosopher than Rousseau, and a more serious one than d’Holbach. And he is the only major Enlightenment writer in whom the combination — the philosopher who is also a novelist, the materialist who is also an art critic, the editor who is also the most dangerous mind on the payroll — feels natural rather than forced.

The trajectory of recent Diderot scholarship has been, on the whole, upward. Andrew Curran’s 2019 biography is, in this writer’s view, the best single-volume account of the man now in any language. P. N. Furbank’s older Diderot: A Critical Biography (1992) is a more idiosyncratic and more rewarding read. For the philosophy, the work of Colas Duflo and the late Jean-Claude Bourdin has done the most to take Diderot seriously as a philosopher rather than as a philosophe.