Morgan Library and Museum, New York

Jean-Baptiste Greuze: Portrait of Denis Diderot, eighteenth century

The most radical thinker of the eighteenth century, Denis Diderot (1713–1784), is not exactly a forgotten man, though he has been long overshadowed by his contemporaries Voltaire and Jean-Jacques Rousseau. After the French Revolution of 1789, the French right routinely blamed every ill of modern life on Voltaire and Rousseau. The expressions “It’s the fault of Voltaire” and “It’s the fault of Rousseau” became so familiar that Victor Hugo could satirize them in a ditty sung by the urchin Gavroche in Les Misérables (1862): “Joy is my character; ’tis the fault of Voltaire; Misery is my trousseau; ’tis the fault of Rousseau.” Voltaire and Rousseau were among the first to be buried in the French Pantheon of the nation’s heroes; Diderot has yet to be, despite a concerted campaign leading up to the three-hundredth anniversary of his birth in 2013.

Diderot was simultaneously too much a man of his time and too much ahead of his time. He devoted the best years of his life to organizing, editing, and writing many of the 74,000 articles of the Encyclopedia (1751–1772), a vast compendium of knowledge amounting to seventeen volumes of text and eleven volumes of plates, and laced with acerbic commentary that alarmed the authorities for attacking religion and subverting government. Known mainly to scholars today, at the time the project served as a thrilling treasury of Enlightenment ideas, if you knew where to find the nuggets hidden under the most unlikely headings. In the article “Nonetheless, However, Nevertheless, Notwithstanding,” for example, Diderot argued that even anti-Christian—i.e., atheist—writers could “nonetheless” be good parents, good friends, and good citizens. Since many articles were unsigned and the known contributors came from every corner of French life, no one could be sure what other ideas were Diderot’s.

As if that exhausting labor were not enough, Diderot anonymously contributed heaps of pages to another sprawling but influential work, this one on European colonialism. The History of the Two Indies appeared under the name of his friend the ex-Jesuit Guillaume Raynal. Diderot’s involvement in turning the second and third editions (1774 and 1780) into incendiary denunciations of European colonialism and the slave trade remained largely unknown before the second half of the twentieth century; the papers he left to his daughter were only inventoried in 1951, thanks to the work of Herbert Dieckmann, a German émigré professor then at Harvard, and scholars are still sorting out what came from Diderot’s pen.

As a man of his time, Diderot loved company and he loved Paris, the very place that Voltaire and Rousseau were always fleeing. His connection, unlike theirs, was not with public opinion but with the people he could talk to: his wife and daughter, his lovers, his countless friends, and, eventually, one ruling monarch in faraway Russia, Catherine the Great. In an age of conversation, he stood out for his volubility. When excited, he could hardly contain himself and would frequently grab his interlocutor’s arm or leg to drive home his point. Catherine found it helpful to keep a table between them during their Saint Petersburg tête-à-têtes. A passionate enthusiast about a staggering range of topics, from science and metaphysics to painting and novels, Diderot tirelessly promoted his colleagues but proved too gullible. For four years he gave work to a penniless copyist who turned out to be a spy planted by the Paris chief of police, a friend of Diderot’s from his school days. In the worst of all betrayals, the Encyclopedia’s publisher secretly bowdlerized the final volumes in order to forestall the censors, leaving its furious editor with no option other than nursing his wounds in private.

Diderot was far from being an intellectual magpie who simply scavenged bits to build a nest out of other people’s ideas. He took seriously his own pronouncement in the article “Encyclopedia” in volume 5:

I have said that an Encyclopedia could only be attempted in a philosophical century; and I said it because this work requires a more courageous spirit than can commonly be found in centuries of pusillanimous taste. We must examine everything, stir up everything without exception and without restraint.

When he roused the authorities with his first novel (The Indiscreet Jewels, 1748, the “jewels” being vaginas that talked when bidden by a magic ring) and a deliberately provocative philosophical tract (Letter on the Blind, 1749), which even Voltaire found too boldly atheistic, the thirty-five-year-old transplant from the provinces was sent to prison by royal command. The king did not need to specify the charge or set the term. Diderot could conceivably have languished there forever.

The budding iconoclast was released within the year; he quickly learned his lesson and from then on kept his most daring works in the drawer or made them available only in an underground newsletter of exquisitely limited circulation. In 1753 his German friend Friedrich Melchior Grimm took over from Raynal a manuscript newsletter entitled Nouvelles littéraires on cultural developments in Paris. Grimm renamed it Correspondence littéraire, philosophique et critique, had each edition copied by hand outside France, and sent it to some fifteen crowned heads of Europe who craved accounts of what was happening behind the scenes in Paris. Diderot included his extensive art criticism and early drafts of many of his most audacious works in Grimm’s confidential pages, and even helped produce the newsletter after 1769. As a consequence, though he did publish rather insipid plays (one of which had some success) and scattered writings on philosophy, painting, novels, and poetry, the deeply heterodox nature of Diderot’s thought could only be whispered until more than a decade after his death in 1784. Some works popped up in the nineteenth century, and a few were only published in the 1950s. The historical identity of “Diderot” is still a work in progress.


When three of his most uncompromising works came to public attention in 1796, they inspired wildly divergent reactions, which is hardly surprising given their subject matter. The Nun is political commentary disguised as a licentious novel of convent life, including scenes of lesbian sex. Jacques the Fatalist and His Master is a reflection on fiction and a philosophical meditation on determinism composed in the form of a novel. Supplement to the Voyage of Bougainville offers cheeky discussions of sexuality and cultural relativism under the guise of travel literature. For conservatives, these writings proved that the Enlightenment had caused the depravities, as they saw them, of the French Revolution, especially the paroxysm of anticlericalism in the de-Christianization movement of 1793–1794 and the general overturning of a society based on hierarchy and deference. Those most enthusiastic about Diderot were, in fact, the anticlerical republicans who still maintained a tenuous grip on power before the rise of Napoleon Bonaparte. Their leading journal published a poem by Diderot, “The Eleutheromaniacs” (maniacs for freedom), that included notorious lines suggesting that the world would be a better place when the last king was strangled with the entrails of the last priest (literally, “his hands would weave the entrails of the priest, lacking a cord for strangling the kings”).

No wonder then that Diderot was one of Marx’s favorite authors. The father of communism was particularly fond of Rameau’s Nephew, a work that only became known when Goethe published a German translation of it in 1805 (the first French publication in 1821 was actually a translation of Goethe’s version). Goethe, Hegel, and Marx were all deeply impressed by this satirical novel, though in different ways. In it, the nephew of the immensely influential composer Jean-Philippe Rameau (1683–1764) carries on a running dialogue with “me” (Diderot) in which “him” (Rameau’s nephew, an actual person fictionalized for Diderot’s purposes) mocks every traditional verity. The point of life, for “him,” was “to keep emptying one’s bowels easily, freely, pleasurably, copiously every night.” Priests at your funeral were a waste of time, since “a dead man doesn’t hear the bells tolling.” By implication there is no afterlife. Goethe found the book brilliant and impudent. For Hegel, “him” incarnated the self-alienated spirit that had to be overcome in order to achieve true freedom, while Marx found most attractive Diderot’s materialism—the idea that all of nature, including humans, is simply matter in motion. Without materialism, there is no Marxism.

Making sense of these mercurial works is not easy, and situating them in such a life as Diderot’s is even more challenging, so it is remarkable that in Diderot and the Art of Thinking Freely Andrew Curran succeeds admirably in both regards. He is far from the first to take on the task, and he makes no inflated claims for his originality. What he offers is the most accessible version of the life and work of this protean figure who trained for the priesthood and ended up questioning every imaginable orthodoxy. To get a handle on the daunting range of Diderot’s interests, Curran divides the life into two parts. The first is basically chronological, starting from the writer’s origins in Langres, a sleepy town in eastern France about two hundred miles from Paris, and continuing through the years of the Encyclopedia. The second part is more thematic and moves from the writings on morality and art criticism to those on sexuality, love, politics, and the origins of the world.

Diderot’s early years gave little hint of what was to come. His father made knives and surgical instruments. One sister entered a convent; his only surviving brother (five of nine children died in childhood) became a priest, and a very conservative, disapproving one at that. Diderot studied with the Jesuits and then went to Paris at age nineteen to continue his courses in theology, but after no fewer than five years at the Sorbonne he drifted away without explanation and took work for a time for a lawyer, then as a mathematics tutor. Reading furiously in mathematics, physics, and natural history and teaching himself Italian and English when he was not frequenting cafés, Diderot only began to settle into his calling as a gadfly intellectual in his late twenties. He translated a history of ancient Greece from English, became fast friends with his fellow chess player Rousseau, and married against his family’s wishes a slightly older woman of modest means, Anne-Antoinette Champion.


The marriage lasted, despite Diderot’s frequent complaints to his friends and his unapologetic philandering, largely because it produced a daughter adored by her father (three other children died). The friendship with Rousseau, on the other hand, eventually foundered. Thin-skinned and susceptible to obsessive fears of persecution, Rousseau ended up breaking off with almost everyone he knew, but Diderot especially resented the way Rousseau slighted him in public while fawning over him in private. Given the differences in their positions (the deist vs. the atheist, the critic of all theater vs. the earnest playwright), the rupture might have seemed inevitable, yet neither of them felt it to be so and both felt deeply wounded on a personal rather than a philosophical level.

Like almost everyone else, Rousseau had no idea what Diderot was writing in secret, and he surely would not have approved of Diderot’s atheism, materialism, or ribaldry. The second half of Curran’s title—“the art of thinking freely”—has to be understood as something much more intensely threatening than simply challenging the status quo. Diderot started from a place that hardly any of his contemporaries ever reached. Voltaire ridiculed the bigotry and intolerance of the Catholic Church; Diderot wanted to know what the foundation of virtue would be without churches or gods. In Rameau’s Nephew, begun about the same time that Rousseau was publishing his best-selling sentimental novel, Julie, or the New Heloïse (1761), Diderot put his personal philosophy of materialism to the test by offering the most cynical and facetious version possible of it in the character of “him.” The Diderot character (“me”) is repeatedly pushed back on his heels as he tries to salvage any sense of morality: What can be the argument for doing good when our actions are predetermined by our inner natures and our upbringing? If humans are simply matter in motion, then can life be anything other than the war of all against all with the spoils going to the victor?

Diderot grasped more firmly than anyone else of his time the significance of the emerging secular worldview that is now commonly associated with modernity: reason, not tradition or the word of God, is the only tool that can be trusted for investigating the world, and human nature is the best foundation for morality, social and sexual relations, and government. As the Tahitian elder Orou says in Supplement to the Voyage of Bougainville, “What do you mean by those words, fornication, incest, and adultery?” When the Catholic chaplain replies, “They are crimes, horrible crimes for which people are burned at the stake in my country,” Orou responds that one cannot condemn the morals of Tahiti for not being those of Europe. “You need a more dependable rule of judgment than that.” He suggests “general welfare and individual utility.” How then, he asks, are fornication, adultery, or even incest crimes? Diderot truly intended to question everything.

Although Curran is alert to Diderot’s penchant for constantly interrupting his own train of thought, his emphasis on the philosophical logic of Diderot’s ideas obscures the role of aesthetics in everything that he touched, not just in his art criticism. Curran seems surprised by Diderot’s quest for a moral foundation for the fine arts, but this is only surprising if you fail to recognize that aesthetics was crucial to the transformation of worldview underway in his time. The true, the good, and the beautiful had to be connected, but now with materialist reasoning. Rameau’s nephew affirms this in his usual irreverent way: “The gates of hell will never prevail against the imperial power of nature and my trinity. The true establishes itself gently—it’s the father and gives birth to the good, who is the son, and from him comes the beautiful, which is the Holy Ghost.”

Diderot was drawn to plays, novels, painting, sculpture, and poetry because he sensed that the charisma of the sacred was being drained away from churches and crowns and filtering down toward the ordinary things of life. Aesthetics was the realm in which the ordinary would be sanctified. We may now find the moralism of Diderot’s drama or his preference for Greuze over Boucher heavy-handed, but he was onto something bigger: transcendence through absorption in the moment, whether by watching a play, reading a novel, or beholding a painting. As a consequence, he was also fascinated by dreaming and the capacity of the arts to throw people into a kind of dream state.


A copperplate engraving from the fencing section of Denis Diderot’s Encyclopedia, 1779

Dreaming appears in much of Diderot’s writing, but it is at the center of D’Alembert’s Dream (first published in 1830), another fantastical work using the names of real-life people, in this case to make points about materialism and the uncertainty of identity, as well as the evolution of species and the possibility of life on other planets. In a delirious state of dreaming in which he can nonetheless speak, Jean Le Rond d’Alembert, the original coeditor of the Encyclopedia and a noted mathematician, muses about his identity, which Diderot had tried to convince him was, like everything else in nature, simply the product of matter in motion, in this case of memory as the brain’s system of organization that gives coherence to the disparate moments of an individual’s life. D’Alembert’s babblings are jotted down by Mademoiselle de l’Espinasse, rumored to be d’Alembert’s mistress. Like d’Alembert, the real-life woman was furious when she heard talk of the work, and well she might have been, since one scene recounts her befuddlement when d’Alembert apparently masturbates while muttering that he wished humans could reproduce as fish do, by simply scattering their seed.

We do not know if Catherine the Great read D’Alembert’s Dream when a draft of it appeared in 1782 in the pages of Grimm’s newsletter. She was a proud subscriber, but by then Diderot had come and gone from Saint Petersburg, and she had cooled in her ardor for his ideas. The meetings of the philosopher and “her imperial majesty,” as Diderot called her, took place between October 1773, when he arrived after a gut-churning journey by carriage, and early March 1774, when he left to return home, putting on a brave face despite his failure to affect Catherine’s policies. In a letter to his once greatest love, Sophie Volland, that was written on the way back, he described “this great and kind sovereign”: she had “the soul of Caesar combined with all the seductions of Cleopatra.” Robert Zaretsky, in Catherine and Diderot, sees in this unlikely pairing an opportunity to bring the Enlightenment to life, and for the most part his effort sparkles despite a propensity to quip at all costs (what is the point, for example, of remarking that “Diderot was a mensch”?).

Zaretsky is a great storyteller, however, and he has chosen to tell a story that still astonishes. A minor German princess marries the heir to the Russian throne at age fifteen, consoles herself in her loneliness by reading Montesquieu and Voltaire, and within months of her husband’s accession, the now thirty-three-year-old marches in full military dress at the head of several regiments to force his abdication in favor of herself and her son. The hapless husband conveniently dies a few days later, officially of an attack of hemorrhoids. Catherine II went on to govern with an iron hand even while courting the favorable opinion of the enlightened world to the west. She corresponded frequently with Voltaire, Grimm, and Madame Geoffrin, a salon hostess at the center of the Parisian social and intellectual world. The empress established her Enlightenment bona fides by personally translating and publishing works that were banned in France. She wrote plays, librettos for operas, essays on Russian history, and a primer for the schools; most important of all, she advertised her fervent desire to oversee the reform of the most backward of all European societies.

The empress was repaid with something akin to adoration. Voltaire objected to her choosing the name Catherine (she was born Sophia) because she was more like a Juno, Venus, Ceres, or Minerva. En route to Saint Petersburg, Diderot wrote to his patroness, “We are the secular missionaries who preach the cult of Saint Catherine.” Like many others, he believed that she would remake her adoptive country, and he thought he could guide her to undertake the right measures by the sheer brilliance of his discourse, though he also put together various memoranda for her consideration.

He had reason to be confident. As soon as she took the throne in 1762, Catherine invited him to Russia to complete the embattled Encyclopedia, and she even considered subsidizing a new version of it. The empress had already bailed him out of financial precarity by offering to buy his library, letting him keep it for his lifetime, and paying him a pension to look after it. In gratitude he had acted as her art agent and helped her amass the old masters at the heart of the Hermitage collection.

When he finally arrived in Russia, Diderot was granted almost inconceivable access, seeing the empress alone day after day for three hours at a time. Since no secretary wrote down the gist of these conversations, Zaretsky has to piece them together from comments in various letters and memoirs, and he does so almost seamlessly. Catherine found her visitor endlessly stimulating: “I could speak to him for the rest of my life and never grow tired of him.” Yet she did weary of him, in part because she faced dangerous challenges to her rule, from the great Pugachev peasant rebellion that raged all through Diderot’s visit to various court conspiracies. She eventually dropped the idea of a new Encyclopedia, and in retrospect she professed to find the philosopher’s ideas unworkable: “Had I placed faith in him, every institution in my empire would have been overturned; legislation, administration, politics and finance would all have been changed, for the purpose of substituting some impracticable theories.” For his part, Diderot maintained a guarded silence after his departure, though he wrote to a friend that “I would be an ingrate if I spoke ill of [Russia],” but “I would be a liar if I spoke well of it.” Even if Catherine had agreed with every one of his proposals, she had learned early on that she could not hope to reform Russia on her own. She did what she could and rarely second-guessed herself.

Curran and Zaretsky both give excellent accounts of Diderot’s works and their place in the writer’s life, but the narrative nature of their accounts can obscure his significance for us now. Diderot thought of himself as a modern-day Socrates, though one who was to be known by his own posthumous writings. These reveal him to be more than just one of many founding fathers of modernity; he was also the first postmodernist. Long before René Magritte painted The Treachery of Images (1929), choosing the phrase “Ceci n’est pas une pipe” to draw attention to the act of painting and its curious relationship to representation, Diderot had titled one of his short stories “Ceci n’est pas un conte” (This is not a story). In it he introduces a fictional reader to interrupt the flow of the story and in this way draw attention to the necessary negotiation between author and reader. Diderot aimed to reveal the workings of aesthetic forms themselves, whether in fiction, painting, or sculpture, and like many later thinkers (from Friedrich Nietzsche to Jacques Derrida) he was convinced that aesthetics afforded privileged access to philosophical problems.

Diderot wrote his most powerful works as dialogues so that he could unsettle any sense of stable truth or clearly defined categories. In Jacques the Fatalist, for example, the servant Jacques is the one with ideas, intelligence, and energy. The master, who has no name, is a foil for Jacques and his theories of determinism. Decades before Hegel, Diderot showed that the master–servant relationship is mutually constituted, which means that it incorporates within itself the means of its own destruction in favor of equality. Even while fighting for the power of reason, science, and knowledge, Diderot saw that these had their own inherent fragilities. If the human race is a cosmic accident, then what is the meaning of life? If our individual lives are predetermined by material circumstances, then what is the space for human freedom of action? Do reason, science, and knowledge ultimately tell us that we are not free after all? Diderot was never afraid to look into the abyss.

He had to hide the true significance of his work during his own lifetime, and he wrote for posterity in dialectical and often self-contradictory ways that make it hard for most readers to get a clear sense of his meanings. But it’s no accident that Diderot studies took off after World War II, for he is distinctly a thinker for our times.