Denis Diderot: philosophe and encyclopedist
Denis Diderot (1713–1784) exemplified the Age of Enlightenment in Europe. But what was the Enlightenment about? I like Immanuel Kant’s (1724–1804) answer.
Enlightenment (Aufklärung) is man’s emergence from his self-incurred immaturity. Immaturity is the inability to use one’s own understanding without the guidance of another. This immaturity is self-incurred if its cause is not lack of understanding, but lack of resolution and courage to use it without the guidance of another. The motto of enlightenment is therefore: Sapere Aude! Have courage to use your own understanding.
Dare to know! That’s what Denis Diderot did all his life with his writings and the Encyclopedie, perhaps his greatest gift to posterity. Encyclopedie encapsulates the spirit of the Enlightenment because it celebrates reason over blind faith. Diderot was born and raised in a bourgeois family of fabricators of cutlery in Langrés. His father Didier Diderot was famous in eastern France as a manufacturer of surgical instruments. Denis admired his father’s hard work and moral values though he did not adopt his father’s profession. Early in childhood Denis’s parents saw in him a startling intellect not fit to be a cutler or tanner. They began to prepare him for priesthood. At the age of ten Denis was enrolled at the Jesuit College in Langrés. After three years at the college, the next step was to join the priesthood as an abbot. In less than two years, one of his uncles tried but failed to get him promoted to his own position as a canon. Denis stayed at the college to complete his final year. He was a brilliant but bothersome student for the teachers. He showed little respect for authority except of his father.
After graduating from the Jesuit College, Diderot had to find a career. A Jesuit priest encouraged him to go to Paris and join the Society of Jesus. But his father intervened at the last minute when Denis was about to leave for Paris. It was on his father’s terms that Denis went to the city along with his father in the early part of 1729. He was enrolled at the college d’Harcourt. in the Latin Quarter. After three years of study, he received what would today be a bachelor’s degree. Soon after that he joined the Sorbonne, the college of theology at the University of Paris. There Denis was emerging as a critical thinker and a sceptic. The Church dogma lost its appeal to his intellect. By 1735, at the age of twenty-two, he had abandoned the idea of becoming a priest. But he wasn’t sure if he wanted to join any profession. He joined a law office, where he spent most of his time reading Greek, Latin, and mathematics and learning English and Italian. Seeing his lack of interest in the practice of law, Diderot’s employer wrote to his father. Denis told his father that his only interest was in studying and nothing else!
He left the law office and, to support himself, he started tutoring the children of a wealthy banker. But it ended soon because Diderot was bored. In a state of boredom, he adopted a lifestyle of a vagabond doing little and drawing money from the family. He spent the next five years courting women, shortchanging Carmelite monks, fighting his parents to get married to a woman they did not approve, and spending time incarcerated in Langrés for a while. Denis walked back to Paris in the fall of 1743 and married the girl of his choice, Anne-Antoinette Champion, a seamstress and lace maker. This was a turning point in his life. He had to look after a young family, and he did so financially without spending too much time at home.
Intellectually Diderot turned into apostasy: rejecting his faith in Christianity by rational thinking. He expressed his anti-religious sentiments in his novel, The Nun, a biting satire on the hypocrisy of religious life. He was also getting into the literature on freethinking. Voltaire, in Letters Concerning the English Nation, became Diderot’s guide to the philosophic and scientific writings in the English language. Sir Isaac Newton (1643–1727) had the greatest impact on his thinking. Diderot started translating the works in English, of which Earl of Shaftsbury’s An Inquiry Concerning Virtue And Merit was a risky but important enterprise. He dedicated the translated book to his brother Didier-Pierre, who was antagonistic to Denis’s views on religion. Shaftsbury’s point was that human beings were endowed with a moral sense that allowed them to know virtue; it instigated them to do virtuous acts because it produced pleasure and happiness. This was not a Christian view!
The translation was published in 1745 when Diderot was estranged with his family in Langres for over two years. In the meantime, he had acquired a mistress while he was living with his wife in difficult circumstances. Apparently, his mistress encouraged him to write a book that would bring Diderot to public’s attention. The book, Philosophical Thoughts, was published in 1746. It included sixty-two short essays on deism, scepticism, and atheism. The dominant voice in the book is of the sceptic without assaulting Catholicism or God. And yet the Paris Parlement condemned the book and burnt it. Some Christians wrote books refuting Diderot’s arguments. The result was that the authorless book sold well: six editions appeared in the next three years!
By this time, Denis Diderot was on the ancien régime’s police watch. Three years later he published yet another book, Letter on the Blind, that aimed at refuting the existence of God which he had not done in Philosophical Thoughts. He sent copies to Rousseau and Voltaire. The story is of a blind Englishman and his debate with a priest who had come to give the blind man his last rites. The blind man ridicules the religious fairy tales:
If we think a phenomenon is beyond man, we immediately say that it’s God’s work; our vanity will accept nothing less, but couldn’t we be a bit less vain and a bit more philosophical in what we say? If nature present us with a problem that is difficult to unravel, let’s leave it as it is and not try to undo it with the help of a being who then offers us a new problem, more insoluble than the first.
The blind man has a different vision: that of chance and godlessness. In a state of delirium, his vision is that the universe has its origin in the “fermenting matter.” He adds:
Come with me to the edge of this universe, beyond the point where I can feel and you can see organised beings; wander across that new ocean with its irregular and turbulent movement and see if you can find in them any trace of that intelligent being whose wisdom you admire here.
The book came out at a time of anxiety and tension in France. So, the Minister of Censor decided to make Diderot an example. There was already a police file on him. Diderot was imprisoned at Vincennes where he spent 102 days. During this time, he corresponded with the government and his father, and he had visits by Rousseau. When he was released from the prison, he gave an undertaking not to publish the kind of anti-religious works for which he spent time incarcerated. He kept his promise! Diderot was determined to spread the word about the “joys of freethinking.” His transformation from scepticism to atheism was now complete. The opportunity to express freethinking came towards the end of 1749 when a prominent French printer and bookseller offered him to translate an English encyclopedia.
Compendia of knowledge, encyclopedias, had a long history going back centuries in China and in Europe in the Middle Ages. By the beginning of the eighteenth century much knowledge had accumulated, and more was being produced and disseminated more quickly. Pierre Bayle (1647–1706) published his four-volume Dictionary from 1695 to 1702. It was a kind of bibliographical digest with long footnotes in which the author showed his skills of rational argument and deception to avoid censor. The author never revealed his own religious inclinations. The Dictionary was read widely and greatly admired by Voltaire, Gibbon, Lessing, and Diderot.
In 1728, Ephraim Chambers (1680–1740) published his Cyclopedia in two volumes. He divided knowledge into “Natural and Scientifical” or “Artificial and Technical” and excluded history and biography. The two groups were subdivided into ‘sensible’ and ‘rational’. The Cyclopedia was very well received in England. It caught the attention of a French printer and bookseller. He wanted to translate it together with the translation of John Harris’s Universal English Dictionary of Arts and Sciences published in 1704. It contained material on mathematical subjects, navigation, optics, gunnery, and architecture. The task ended up at the desk of Denis Diderot assisted by Jean-Baptiste d’Alembert who was a star while Diderot was not. The task of translation morphed into a completely new and audacious project called the Encyclopedie. It would develop into an unprecedented compendium of knowledge in the French language.
The Encyclopedie was an enormous project; it kept Diderot occupied for more than twenty-five years. Eventually it appeared in seventeen volumes of text running to 18,000 pages with more than 20 million words. One hundred and fifty contributors wrote 74,000 articles, arranged alphabetically with cross references (or 62,000 links). In addition, it had eleven volumes of 2,885 illustrations, including 1,900 engraved plates illustrating technical processes and conveying satirical messages. While Diderot was busy writing articles for the first two volumes, d’Alembert prepared the “Preliminary Discourse”, or an introduction to the Encyclopedie. The Discourse would shift the cultural and intellectual landscape of Europe. It was a mind-based organisation of human knowledge. d’Alembert divided knowledge into three groups: memory, reason, and imagination. Memory included history, ecclesiastical, natural, and civil. Reason had the largest variety, including the study of God, man, and nature. Imagination was very small, but the amount of space arts received compensated for the smallness. In the Discourse, d’Alembert’s gives the intellectual ancestry of the project: it includes Francis Bacon, Sir Isaac Newton, John Locke, and René Descartes.
The first two volumes appeared in 1751 and 1752. There were attacks on these volumes by Jesuits, courtiers, and the Pope throughout the 1750s. In 1757 — a year full of tension and trouble in France because a deranged man tried to kill King Louis XV (1707–1774) — volume seventh of the Encyclopedie included an article by d’Alembert on Geneva that became the target of anger in France and Switzerland. Two years later, the Pope put the Encyclopedie on the index of banned books and its sale in France was made illegal. In response, d’Alembert removed himself from the project, but Diderot and his other collaborators decided to continue. In 1765 the last ten volumes were published. (The volumes of the illustrated plates were completed in 1772). Diderot was not happy with these volumes because the printer had excluded or edited several articles written by Diderot and his collaborators. He thought his labour of twenty-five years had been wasted. But Encyclopedie became the ‘Bible’ of Enlightenment in France, Europe, and the rest of the world!
We should note four things about the Encyclopedie. First, it covered almost every aspect of knowledge, however controversial, and was organised alphabetically, meaning subjects were mixed. Second, the articles were written by prominent philosophes and specialists, people who knew their subject and had the courage to contribute their ideas. Third, Denis Diderot was the captain of the project as writer, editor, and manager. It’s fair to say that the Encyclopedie and Diderot were synonymous. Fourth, throughout the publication of the Encyclopedie, from volume one in 1751 to the last one in 1772, its editor and contributors were under the watch of the project’s critics and the Ministry of Censor. The Censor had to pass every page of the Encyclopedie to be published with royal privilege. The more they attempted to damage the project the more it drew public’s attention and made money for the publishers.
After some of the major contributors left the enterprise, Diderot continued his struggle, in secret and in fear of arrest, to publish the future volumes. He and his collaborators managed to produce a work that embodied the central ideals of the Enlightenment. More than that. It shifted the conception of knowledge: marginalised theology; moved from abstruse learning to knowledge that was practical and useful; uncovered the knowledge that the guilds had kept hidden — it ended the guilds. The Encyclopedie gave a new conception to science: ‘understanding the material world and its capacity for change.’ It’s not clear if the Encyclopedie was within the reach of all readers because its volumes were expensive. For most readers, the only accessible venue was a public library.
While he was up to his neck in the affairs of Encyclopedie, Diderot continued writing as an independent author. He wrote a book on the gestural origins of language in 1751. Two years later he wrote On the Interpretation of Nature, a collection of essays on scientific methodology or a radical investigation of nature. This book was his last work of philosophy. Diderot then turned his attention to writing plays. In 1757, he wrote a moralistic drama titled The Natural Son, or The Trials of Virtue; he supplemented it with a dialogue between himself and the Natural Son. It was an innovative drama shaking the conventional characters in the French plays. He followed it with two bourgeois dramas: a moral story that has a happy ending and highlights the ‘unpretentious nobility’ of the French lower and middle classes. His plays were well received and staged with great success. Apparently, he was trying to promote family values and repairing his own reputation as an anti-religionist.
To counter a satirical attack on his last play, Diderot crafted an unpublishable manuscript, Rameau’s Nephew — a dialogue that exposed the hypocrisy of life including his own role as a philosophe. It came into being because Diderot was willing to subject his own beliefs to the same method of interrogation as he had used on religion. Rameau’s Nephew conveys the right of an individual to reject any worldview that impinges on the right to live freely. Realising the explosive nature of the message in the dialogue, Diderot put it under lock and key. But in the 1780s, at least three copies of the manuscript were distributed. In 1801, a copy landed in the hands of the German philosopher, poet, and playwright Friedrich Schiller (1759–1805). He passed it on to Johann Wolfgang Goethe (1749–1832) who claimed that he had never seen anything ‘more insolent and more restrained, more talented and more audacious, more immorally moral.’ Goethe translated it into German in 1805. Eventually, as Goethe thought, it exploded like a bomb ‘right in the middle of French literature.’
Diderot also took over the role of an art critic for Melchior Grimm’s (1723–1807) Literary Correspondence from 1759 to 1781. He spent more time in and around the Louvre outside the Salon season. The biennial Salon was an experience that exhilarated but drained Diderot. He studied numerous books and treatises on art like he studied medicine, natural history, music, and mathematics. In addition, he visited museums and galleries to see paintings and other pieces of art. And he spent time talking to the artists. Grimm’s Correspondence carried the voice of Diderot to various courts throughout Europe. The most important message he conveyed about art was to question the conventions of the academies and to turn the viewing of art as a personal experience. Diderot’s unconventional writings on the aesthetics of art remain a major attraction for the art scholars today.
Diderot moved on from art in 1759 to science fiction about the godless origin of Homo sapiens. The idea was part of the questions he was asking about life and nature. What is life? What are we? Where did humans come from? Are we changing? And so on. The trigger for the science fiction was a gathering at his friend Baron d’Holbach’s elegant mansion in 1769. Despite the pressure of work of editing the Encyclopedie, Diderot managed to compose a mischievous play called D’Alembert’s Dream. It developed into a three-act materialist drama with characters including himself, d’Alembert, Mademoiselle de Lespinasse and Théophile de Bordeu, an eminent physician. The play highlights a materialist conception of the universe and refutes the religious conception of creation: that the universe was created some six thousand years ago; each creature was given an unchangeable identity; and humans were made an exceptional species by God’s grace. Diderot refuted these widely held religious beliefs in the light of the ideas of Carl Linnaeus (1707–1778), the Swedish naturalist, and Comte de Buffon, keeper of the King’s Garden and author of Natural History. In the drama, Diderot goes beyond the compelling arguments for a materialist universe, its origins, and the evolution of life on earth. He dwells on issues of sexuality and love.
Diderot expressed two major regrets in life. First, that he had wasted his best years working on the Encyclopedie. Second, that he was married to a woman who gave him little pleasure. Since he thought that our primary responsibility in life was to be happy, the second regret was the more painful. His love for Anne-Antoinette had burnt out three years after their marriage. Then he fell in love with another woman, like him an author and a freethinker. His relationship with this woman took a toll on his marriage, but he did not give up on his family. One of the reasons was his beloved daughter Angelique. He was in every respect a family man. But he continued extra-marital affairs because he thought they were necessary for pleasure! He left his first mistress in 1755 after four years of courtship. Then he fell in love with a 38-year-old woman whom he called Sophie; their relationship lasted until 1765.
Diderot’s fame as a polymath caught the attention of Empress Catherine the Great (1729–1796) of Russia. She invited him and d’Alembert soon after ascending the throne in 1762. She came to occupy the Russian throne after staging a coup against her brute and alcoholic husband, Peter III (1728–1762), and then murdering him. Catherine had acquired a taste for French culture and literature at a young age. Now she needed to create an image for herself as a benign and progressive ruler of Russia. While Diderot did not go to St. Petersburg until the fall of 1773, Catherine appointed him her Cultural Attaché in 1765. He sent quite a few prominent Frenchmen to Russia and helped the Empress build a massive collection of artwork bought in France and other countries. Catherine rewarded Diderot handsomely, relieving him from financial worries. Eventually Diderot travelled to St. Petersburg in the fall of 1773 and spent a year in that city. There he wrote several essays, included in his collection called Observations, about various reforms in Russia. He also made the case for a university. Catherine did not receive or read the Observations until 1785, a year after Diderot’s death! Diderot realised that Catherine was not serious about changing her autocratic administration or the feudal society. Catherine thought that the philosophe’s ideas were too radical or ill-suited for imperial Russia.
Back in France Louis XV died of smallpox in 1774 after a reign of fifty-one years and his grandson ascended the throne as Louis XVI (1754–1793 ) at the age of nineteen. Diderot was encouraged by the fact that the new king endorsed a series of progressive policies: putting a check on the king’s authority by reinstating the Parlement and appointing reformist counselors and ministers, many of whom were known to or friends of Diderot. The timing, however, was not propitious: prices of grain and bread spiked because of the inefficient markets and poor harvests. Inflation was followed by insurrections, following which the king removed the reformist ministers. Events in France were taking a wrong turn. Diderot’s health also started to decline, but he didn’t stop writing or expressing his views. In 1776, he agreed to write a biographical preface for the works of Lucius Seneca (1BCE-65CE) that Baron d’Holbach had helped to translate into six volumes. In the Essay on the Life of Seneca, Diderot defended Seneca’s support for Nero, somewhat like his own helping hand to Catherine in Russia. In the Essay Diderot also included his invective against Rousseau to preempt the impending publication of Rousseau’s Confessions, in which Diderot was to be a major target. The Essay was published a few months after the death of Rousseau in 1778. The reviewers thought that his attack on Rousseau was petty and unfair. Diderot responded to the reviewers with a new edition of the Essay in 1782, the same year the first volume of Confessions was published. The breakup with Rousseau some twenty-five years earlier came to a sad end for the reputation of both philosophes. Even Diderot’s friends and supporters were not happy with his published views on Rousseau.
Thomas Raynal’s (1713–1796) Philosophical and Political History of the Two Indies, published in three editions, was one of the best-selling books in the last quarter of the eighteenth century. Diderot wrote hundreds of critical pages for its editions of 1771, 1774 and 1780. One-fifth of the third edition of the ten-volume book was contributed by Diderot! He redirected the book’s focus from the Indies to Europe and France in particular. ‘It is no exaggeration that these anonymous contributions to Raynal’s project not only changed the book, but history as well.’ In the second edition, Diderot addressed Louis XVI directly about the powder keg on which he was sitting. He warned the king of the disaster lying ahead: ‘Whenever the sovereign does not allow people to express themselves freely on economic and political subjects, he provides the most convincing evidence of his inclination to tyranny.’ Diderot also wrote on the moral and economic aspects of chattel slavery in the Americas. However, he was an avid supporter of the colonists’ struggle against Britain. In fact, he had expressed these views in the 1760s, long before the ‘Declaration of Independence’ was signed in 1776. Diderot did not live long enough to see the influence of his anonymous contributions would have on the next generation. But he did say the following in the last paragraph of the 1780 edition of the History.
I do not flatter myself into thinking that, when the great revolution comes, my name will survive. . . . This feeble work [the History of the Two Indies], whose sole merit will be to have inspired better books, will undoubtedly be forgotten. But at least I will be able to tell myself that I contributed as much as possible to the happiness of my fellow men, and prepared, perhaps from afar, improvement of their lot. This sweet thought will for me take the place of glory. It will be the charm of my old age and the consolation of my final moment.
By 1783 everyone who had played a role in the Encyclopedie was gone. One consolation Diderot had was that Voltaire met him in Paris a year before the former’s death in 1778. Voltaire and Diderot had corresponded for almost fifty years but never met. Voltaire sent him a note at the end of 1776: ‘I am heartbroken to die without having met you. . . . I would gladly come and spend my last fifteen minutes in Paris in order to have the solace of hearing your voice.’ He came fifteen months later and had a meeting with Diderot who said later that Voltaire was like an ancient ‘enchanted castle whose various parts are falling apart,’ but whose corridors were ‘still inhabited by an old sorcerer.’
Diderot did not fear death for two reasons. First, he was a disciple of Seneca and Michel de Montaigne (1533–1592), the two great Stoics. Second, he was a thoughtful materialist. He celebrated the materialist philosophy in the dialogue-driven Jacques the Fatalist, his last book of fiction. It is as profound a book as it is light-hearted and joyful. We do not have free will; what we do is ultimately determined by the effect of other preceding causes. But we cannot be fatalistic. We act and react. That’s what Jacques and his Captain did in their tour through France.
Diderot died towards the end of July in 1784. Before his death, like other writers and philosophers, he was concerned about posterity’s view of him. He wrote: ‘O holy and sacred Posterity! Ally of the unhappy and oppressed; you are fair, you who are righteous, you avenge the honest man, who unmask the hypocrite, and who punish the tyrant; may your comfort and your steadfastness never forsake me.’ His plays and the Encyclopedie were embraced with great enthusiasm throughout France and in the rest of Europe. But five years after Diderot’s death, leaders of the French Revolution called this tenacious advocate of human rights and freedom an enemy of the people. Why? Apparently, his atheism was the reason. In the next one hundred years after his death, Diderot was portrayed as a godless radical who was responsible for secularism, individualism, and moral decline. France was a theatre of war between the progressives and traditionalists and a playground for the regimes of kings and republics. The tide turned in Diderot’s favour in the last quarter of the nineteenth century during the Third Republic. His influential supporters created his image as a persecuted man of letters and a humanist par excellence. He wanted to ‘reorganise the world without God or a king.’ In 1884, Denis Diderot’s birthday was celebrated with much fanfare all over France for good reason: he represented the soul of the Enlightenment.
 I have consulted: Philipp Blom, A Wicked Company: The Forgotten Radicalism of the European Enlightenment, 2010; Andrew S. Curran, Diderot and the Art of Thinking Freely, 2019; Peter Gay, The Enlightenment, Two Volumes, 1966–1969; and Ritchie Robertson, The Enlightenment: The Pursuit of Happiness 1680–1790, 2021.
 Immanuel Kant was one of the leading lights of the Enlightenment. The others were: George Berkeley (1685–1753); Charles-Louis Montesquieu (1689–1755); Voltaire (1694–1778); Georges-Louis Buffon (1707–1788); David Hume (1711–1776); Jean-Jacques Rousseau ((1712–1778); Denis Diderot (1713–1784); Claude Helvetius ( 1715–1771); Etienne Condillac (1715–1780); Jean-Baptiste d’Alembert (1717–1783); Baron d’Holbach (1723–1789); Adam Smith (1723–1790); Adam Ferguson (1723–1816); Jacques Turgot (1727–1781); Gotthold Lessing ((1729–1781); Joseph Priestley ((1733–1804); Christoph Wieland (1733–1813); Edward Gibbon (1737–1794); Cesare Beccaria (1738–1794); Nicholas de Condorcet (1743–1784); and Friedrich Schiller (1759–1805).
 It was during this aimless period that Diderot first met Jean-Jacques Rousseau. Their friendship and love for each other grew with time. The first signs of rupture between the two started to show in the early 1750s. After that it was all downhill until 1757 when they last exchanged letters.
 Besides their financial woes, they found little in common to which was added Diderot’s infidelity. Anne-Antoinette also lost three children in infancy. Only one girl, born in 1753, survived who was Diderot’s beloved daughter Angelique.
 This project was not the brainchild of Diderot. The idea originally came from Gottfried Sellius, an immigrant from Danzig (now Gdansk in Poland). In 1745, this scholar contacted a French printer and bookseller, André-François le Breton, with the proposition for translating Ephraim Chambers’s Cyclopedia into French. After a period of disappointments, le Breton and three other printers appointed Denis Diderot and d’Alembert as coeditors of the Encyclopedie.
 They included Voltaire, Rousseau, d’Holbach, d’Alembert, François Quesnay, Jacques Turgot, Samuel Formey, and Louis de Jaucourt.
 Baron d’Holbach was a militant atheist and a generous host who organised regular dinner parties for friends at his mansion, the so-called hôtel des philosophes. In these gatherings, the guests engaged in free debate and discussion on all issues under the sun. But what was discussed remained in the hôtel.
 Diderot explored different aspects of human sexuality in some of his writings. A major piece was his novel The Nun which he revisited in 1782. His second famous treatment of sex was in the Supplement to Bougainville’s Voyage. The two novels are at the opposite poles. The Nun is about sexual perversion and repressed desires at the convent. The Supplement is about the openness of sex and its pleasure in Tahiti. The imagined trip to Tahiti is hilarious.
 Diderot’s long and deep friendship with Rousseau ended in an ugly way towards the end of 1757. It had to do with Rousseau’s displeasure with one of the novels of Diderot and Diderot’s displeasure about Rousseau’s attempted affair with the wife of a common friend who was away at war. In his play The Natural Son, Diderot wrote ‘The good man is a member of society and only the evil man is alone.’ It sent Rousseau into a rage. He protested to Diderot who in turn wrote an apology with a twist: that you have lost friends because of suspicion and paranoia you suffer from. By 1758 the breakup was complete — Diderot wrote about Rousseau in his notebook that ‘this man is a monster.’
 Cited by Andrew S. Curran, Diderot and the Art of Thinking Freely, p.373.
 Ibid., p.378.