Denis Diderot

In 1746, Diderot wrote his first original work: the Philosophical Thoughts (Pensées philosophiques).[15][16] In this book, Diderot argued for a reconciliation of reason with feeling so as to establish harmony. According to Diderot, without feeling there is a detrimental effect on virtue, and no possibility of creating sublime work. However, since feeling without discipline can be destructive, reason is necessary to control feeling.[1]^: 625

At the time Diderot wrote this book he was a deist. Hence there is a defense of deism in this book, and some arguments against atheism.[1]^: 625 The book also contains criticism of Christianity.[1]^: 626

In 1747, Diderot wrote The Skeptic's Walk (Promenade du sceptique)[17] in which a deist, an atheist, and a pantheist have a dialogue on the nature of divinity. The deist gives the argument from design. The atheist says that the universe is better explained by physics, chemistry, matter, and motion. The pantheist says that the cosmic unity of mind and matter, which are co-eternal and comprise the universe, is God. This work remained unpublished until 1830. Accounts differ as to why. It was either because the local police, warned by the priests of another attack on Christianity, seized the manuscript, or because the authorities forced Diderot to give an undertaking that he would not publish this work.[1]^: 626

In 1748, Diderot needed to raise money on short notice. He had become a father through his wife, and his mistress Mme. de Puisieux was making financial demands from him. At this time, Diderot had stated to Mme. de Puisieux that writing a novel was a trivial task, whereupon she challenged him to write a novel. In response, Diderot wrote his novel The Indiscreet Jewels (Les bijoux indiscrets). The book is about the magical ring of a Sultan which induces any woman's "discreet jewels"[18][note 1] to confess their sexual experiences when the ring is pointed at them.[1]^{: 626–627} In all, the ring is pointed at thirty different women in the book—usually at a dinner or a social meeting—with the Sultan typically being visible to the woman.[19][1]^: 627 However, since the ring has the additional property of making its owner invisible when required, a few of the sexual experiences recounted are through direct observation with the Sultan making himself invisible and placing his person in the unsuspecting woman's boudoir.[19]

Besides the bawdiness, there are several digressions into philosophy, music, and literature in the book. In one such philosophical digression, the Sultan has a dream in which he sees a child named "Experiment" growing bigger and stronger till it demolishes an ancient temple named "Hypothesis". The book proved to be lucrative for Diderot even though it could only be sold clandestinely. It is Diderot's most published work.[1]^: 627

The book is believed to be an imitation of Le Sopha.[1]^: 627

Diderot would keep writing on science in a desultory way all his life. The scientific work of which he was most proud was Memoires sur differents sujets de mathematique (1748). This work contains original ideas on acoustics, tension, air resistance, and "a project for a new organ" which could be played by all. Some of Diderot's scientific works were applauded by contemporary publications of his time like The Gentleman's Magazine, the Journal des savants; and the Jesuit publication Journal de Trevoux, which invited more such work: "on the part of a man as clever and able as M. Diderot seems to be, of whom we should also observe that his style is as elegant, trenchant, and unaffected as it is lively and ingenious."[1]^: 627

On the unity of nature, Diderot wrote, "Without the idea of the whole, philosophy is no more," and, "Everything changes; everything passes; nothing remains but the whole." He wrote of the temporal nature of molecules, and rejected emboîtement, the view that organisms are pre-formed in an infinite regression of non-changing germs. He saw minerals and species as part of a spectrum, and was fascinated with hermaphroditism. His answer to the universal attraction in corpuscular physics models was universal elasticity. His view of nature's flexibility foreshadows the discovery of evolution, but it is not Darwinistic in a strict sense.[20]

Diderot's celebrated Letter on the Blind (Lettre sur les aveugles à l'usage de ceux qui voient) (1749) introduced him to the world as an original thinker.[21] The subject is a discussion of the relation between reasoning and the knowledge acquired through perception (the five senses). The title of his book also evoked some ironic doubt about who exactly were "the blind" under discussion. In the essay, blind English mathematician Nicholas Saunderson[22] argues that, since knowledge derives from the senses, mathematics is the only form of knowledge that both he and a sighted person can agree on. It is suggested that the blind could be taught to read through their sense of touch. (A later essay, Lettre sur les sourds et muets, considered the case of a similar deprivation in the deaf and mute.) According to Jonathan Israel, what makes the Lettre sur les aveugles so remarkable, however, is its distinct, if undeveloped, presentation of the theory of variation and natural selection.[23]

This powerful essay, for which La Mettrie expressed warm appreciation in 1751, revolves around a remarkable deathbed scene in which a dying blind philosopher, Saunderson, rejects the arguments of a deist clergyman who endeavours to win him round to a belief in a providential God during his last hours. Saunderson's arguments are those of a neo-Spinozist Naturalist and fatalist, using a sophisticated notion of the self-generation and natural evolution of species without Creation or supernatural intervention. The notion of "thinking matter" is upheld and the "argument from design" discarded (following La Mettrie) as hollow and unconvincing. The work appeared anonymously in Paris in June 1749, and was vigorously suppressed by the authorities. Diderot, who had been under police surveillance since 1747, was swiftly identified as the author, had his manuscripts confiscated, and was imprisoned for some months, under a lettre de cachet, on the outskirts of Paris, in the dungeons at Vincennes where he was visited almost daily by Rousseau, at the time his closest and most assiduous ally.[24]

Voltaire wrote an enthusiastic letter to Diderot commending the Lettre and stating that he had held Diderot in high regard for a long time to which Diderot had sent a warm response. Soon after this, Diderot was arrested.[1]^{: 629–630}

Science historian Conway Zirkle has written that Diderot was an early evolutionary thinker and noted that his passage that described natural selection was "so clear and accurate that it almost seems that we would be forced to accept his conclusions as a logical necessity even in the absence of the evidence collected since his time."[25]

Title page of the Encyclopédie

André le Breton, a bookseller and printer, approached Diderot with a project for the publication of a translation of Ephraim Chambers' Cyclopaedia, or Universal Dictionary of Arts and Sciences into French, first undertaken by the Englishman John Mills, and followed by the German Gottfried Sellius.[5] Diderot accepted the proposal, and transformed it. He persuaded Le Breton to publish a new work, which would consolidate ideas and knowledge from the Republic of Letters. The publishers found capital for a larger enterprise than they had first planned. Jean le Rond d'Alembert was persuaded to become Diderot's colleague, and permission was procured from the government.

In 1750 an elaborate prospectus announced the project, and in 1751 the first volume was published.[5] This work was unorthodox and advanced for the time. Diderot stated that "An encyclopedia ought to make good the failure to execute such a project hitherto, and should encompass not only the fields already covered by the academies, but each and every branch of human knowledge." Comprehensive knowledge will give "the power to change men's common way of thinking."[28] The work combined scholarship with information on trades. Diderot emphasized the abundance of knowledge within each subject area. Everyone would benefit from these insights.

Diderot's work, however, was mired in controversy from the beginning; the project was suspended by the courts in 1752. Just as the second volume was completed accusations arose regarding seditious content, concerning the editor's entries on religion and natural law. Diderot was detained and his house was searched for manuscripts for subsequent articles: but the search proved fruitless as no manuscripts could be found. They were hidden in the house of an unlikely confederate—Chretien de Lamoignon Malesherbes, who originally ordered the search. Although Malesherbes was a staunch absolutist, and loyal to the monarchy—he was sympathetic to the literary project.[29] Along with his support, and that of other well-placed influential confederates, the project resumed. Diderot returned to his efforts only to be constantly embroiled in controversy.

These twenty years were to Diderot not merely a time of incessant drudgery, but harassing persecution and desertion of friends. The ecclesiastical party detested the Encyclopédie, in which they saw a rising stronghold for their philosophic enemies. By 1757 they could endure it no longer—the subscribers had grown from 2,000 to 4,000, a measure of the growth of the work in popular influence and power.[5] Diderot wanted the Encyclopédie to give all the knowledge of the world to the people of France. However, the Encyclopédie threatened the governing social classes of France (aristocracy) because it took for granted the justice of religious tolerance, freedom of thought, and the value of science and industry.[30] It asserted the doctrine that the main concern of the nation's government ought to be the nation's common people. It was believed that the Encyclopédie was the work of an organized band of conspirators against society, and that the dangerous ideas they held were made truly formidable by their open publication. In 1759, the Encyclopédie was formally suppressed.[5] The decree did not stop the work, which went on, but its difficulties increased by the necessity of being clandestine. Jean le Rond d'Alembert withdrew from the enterprise and other powerful colleagues, including Anne Robert Jacques Turgot, Baron de Laune, declined to contribute further to a book which had acquired a bad reputation.[21]

Diderot was left to finish the task as best he could. He wrote about 7,000 articles,[31] some very slight, but many of them laborious, comprehensive, and long. He damaged his eyesight correcting proofs and editing the manuscripts of less scrupulous contributors. He spent his days at workshops, mastering manufacturing processes, and his nights writing what he had learned during the day. He was incessantly harassed by threats of police raids. The last copies of the first volume were issued in 1765.

In 1764, when his immense work was drawing to an end, he encountered a crowning mortification: he discovered that the bookseller, Le Breton, fearing the government's displeasure, had struck out from the proof sheets, after they had left Diderot's hands, all passages that he considered too dangerous. "He and his printing-house overseer," writes Furbank, "had worked in complete secrecy, and had moreover deliberately destroyed the author's original manuscript so that the damage could not be repaired."[32] The monument to which Diderot had given the labor of twenty long and oppressive years was irreparably mutilated and defaced.[5] It was 12 years, in 1772, before the subscribers received the final 28 folio volumes of the Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers since the first volume had been published.

When Diderot's work on the Encyclopédie project came to an end in 1765, he expressed concerns to his friends that the twenty-five years he had spent on the project had been wasted.[11]

La Religieuse was a novel that claimed to show the corruption of the Catholic Church's institutions.

The novel began not as a work for literary consumption, but as an elaborate practical joke aimed at luring the Marquis de Croismare, a companion of Diderot's, back to Paris. The Nun is set in the 18th century, that is, contemporary France. Suzanne Simonin is an intelligent and sensitive sixteen-year-old French girl who is forced against her will into a Catholic convent by her parents. Suzanne's parents initially inform her that she is being sent to the convent for financial reasons. However, while in the convent, she learns that she is actually there because she is an illegitimate child, as her mother committed adultery. By sending Suzanne to the convent, her mother thought she could make amends for her sins by using her daughter as a sacrificial offering.

At the convent, Suzanne suffers humiliation, harassment and violence because she refuses to make the vows of the religious community. She eventually finds companionship with the Mother Superior, Sister de Moni, who pities Suzanne's anguish. After Sister de Moni's death, the new Mother Superior, Sister Sainte-Christine, does not share the same empathy for Suzanne that her predecessor had, blaming Suzanne for the death of Sister de Moni. Suzanne is physically and mentally harassed by Sister Sainte-Christine, almost to the point of death.

Suzanne contacts her lawyer, Monsieur Manouri, who attempts to legally free her from her vows. Manouri manages to have Suzanne transferred to another convent, Sainte-Eutrope. At the new convent, the Mother Superior is revealed to be a lesbian, and she grows affectionate towards Suzanne. The Mother Superior attempts to seduce Suzanne, but her innocence and chastity eventually drives the Mother Superior to insanity, leading to her death.

Suzanne escapes the Sainte-Eutrope convent using the help of a priest. Following her liberation, she lives in fear of being captured and taken back to the convent as she awaits the help from Diderot's friend the Marquis de Croismare.

Diderot did not use the novel as an outlet to condemn Christianity, but as a way to criticize cloistered life.[13] In Diderot's telling, the Church fostered a hierarchical society, prevalent in the power dynamic between the Mother Superior and the girls in the convent. Girls were forced against their will to take their vows and endure the intolerable life of the convent. Diderot highlighted the victimization of women by the Catholic Church. Their subjection to the convent dehumanized them and represses their sexuality. Furthermore, the novel took place during a time in France when religious vows were regulated and enforced by the government. Through his cross-identification writing style, Diderot manifested the demeaning Catholic standards towards women that forced them to obey their determined fate under the hierarchical society.

Although The Nun was completed in about 1780, the work was not published until 1796, after Diderot's death.

The dialogue Rameau's Nephew (French: Le Neveu de Rameau) is a "farce-tragedy" reminiscent of the Satires of Horace, a favorite classical author of Diderot's whose lines "Vertumnis, quotquot sunt, natus iniquis" ("Born under (the influence of) the unfavorable (gods) Vertumnuses, however many they are") appear as epigraph. According to Nicholas Cronk, Rameau's Nephew is "arguably the greatest work of the French Enlightenment's greatest writer."[34]

Un dîner de philosophes painted by Jean Huber. Denis Diderot is the second from the right (seated).

The narrator in the book recounts a conversation with Jean-François Rameau, nephew of the famous Jean-Philippe Rameau. The nephew composes and teaches music with some success but feels disadvantaged by his name and is jealous of his uncle. Eventually he sinks into an indolent and debauched state. After his wife's death, he loses all self-esteem and his brusque manners result in him being ostracized by former friends. A character profile of the nephew is now sketched by Diderot: a man who was once wealthy and comfortable with a pretty wife, who is now living in poverty and decadence, shunned by his friends. And yet this man retains enough of his past to analyze his despondency philosophically and maintains his sense of humor. Essentially he believes in nothing—not in religion, nor in morality; nor in the Roussean view about nature being better than civilization since in his opinion every species in nature consumes one another.[1]^: 660 He views the same process at work in the economic world where men consume each other through the legal system.[1]^{: 660–661} The wise man, according to the nephew, will consequently practice hedonism:

Hurrah for wisdom and philosophy!—the wisdom of Solomon: to drink good wines, gorge on choice foods, tumble pretty women, sleep on downy beds; outside of that, all is vanity.[1]^: 661

The dialogue ends with Diderot calling the nephew a wastrel, a coward, and a glutton devoid of spiritual values to which the nephew replies: "I believe you are right."[1]^: 661

Diderot's intention in writing the dialogue—whether as a satire on contemporary manners, a reduction of the theory of self-interest to an absurdity, the application of irony to the ethics of ordinary convention, a mere setting for a discussion about music, or a vigorous dramatic sketch of a parasite and a human original—is disputed. In political terms it explores "the bipolarisation of the social classes under absolute monarchy," and insofar as its protagonist demonstrates how the servant often manipulates the master, Le Neveu de Rameau can be seen to anticipate Hegel's master–slave dialectic.[35]

The publication history of the Nephew is circuitous. Written between 1761 and 1774, Diderot never saw the work through to publication during his lifetime, and apparently did not even share it with his friends. After Diderot's death, a copy of the text reached Schiller, who gave it to Goethe, who, in 1805, translated the work into German.[21] Goethe's translation entered France, and was retranslated into French in 1821. Another copy of the text was published in 1823, but it had been expurgated by Diderot's daughter prior to publication. The original manuscript was only found in 1891.[1]^: 659

Diderot's travel from Paris to Saint Petersburg in 1773–1774. The blue line marks the outward from 3 June 1773 until 9 October 1773, and the red line marks the return journey 5 March 1774 to 21 October 1774.

When the Russian Empress Catherine the Great heard that Diderot was in need of money, she arranged to buy his library and appoint him caretaker of it until his death, at a salary of 1,000 livres per year. She even paid him 50 years salary in advance.[11] Although Diderot hated traveling,[1]^: 674 he was obliged to visit her.[1]^: 448

On 9 October 1773, he reached St. Petersburg, met Catherine the next day and they had several discussions on various subjects. During his five-month stay at her court, he met her almost every day.[41]^{: 448–449} During these conversations, he would later state, they spoke 'man to man'.[41]^: 448[note 3]

He would occasionally make his point by slapping her thighs. In a letter to Madame Geoffrin, Catherine wrote:

Your Diderot is an extraordinary man. I emerge from interviews with him with my thighs bruised and quite black. I have been obliged to put a table between us to protect myself and my members.[41]^: 448

One of the topics discussed was Diderot's ideas about how to transform Russia into a utopia. In a letter to Comte de Ségur, the Empress wrote that if she followed Diderot's advice, chaos would ensue in her kingdom.[41]^: 448

When returning, Diderot asked the Empress for 1,500 rubles as reimbursement for his trip. She gave him 3,000 rubles, an expensive ring, and an officer to escort him back to Paris. He wrote a eulogy in her honor upon reaching Paris.[41]^: 449

In 1766, when Catherine heard that Diderot had not received his annual fee for editing the Encyclopédie (an important source of income for the philosopher), she arranged for him to receive a massive sum of 50,000 livres as an advance for his services as her librarian.[11]

In July 1784, upon hearing that Diderot was in poor health, Catherine arranged for him to move into a luxurious suite in the Rue de Richelieu. Diderot died two weeks after moving there—on 31 July 1784.[41]^: 893

Among Diderot's last works were notes "On the Instructions of her Imperial Majesty...for the Drawing up of Laws". This commentary on Russia included replies to some arguments Catherine had made in the Nakaz.[41]^: 449[43] Diderot wrote that Catherine was certainly despotic, due to circumstances and training, but was not inherently tyrannical. Thus, if she wished to destroy despotism in Russia, she should abdicate her throne and destroy anyone who tries to revive the monarchy.[43] She should publicly declare that "there is no true sovereign other than the nation, and there can be no true legislator other than the people."[44] She should create a new Russian legal code establishing an independent legal framework and starting with the text: "We the people, and we the sovereign of this people, swear conjointly these laws, by which we are judged equally."[44] In the Nakaz, Catherine had written: "It is for legislation to follow the spirit of the nation."[44] Diderot's rebuttal stated that it is for legislation to make the spirit of the nation. For instance, he argued, it is not appropriate to make public executions unnecessarily horrific.[45]

Ultimately, Diderot decided not to send these notes to Catherine; however, they were delivered to her with his other papers after he died. When she read them, she was furious and commented that they were an incoherent gibberish devoid of prudence, insight, and verisimilitude.[41]^: 449[46]

• Diderot, Denis, ed. A Diderot Pictorial Encyclopedia of Trades and Industry, Vol. 1 (1993 reprint) excerpt and text search
• Diderot, Denis. Diderot: Political Writings ed. by John Hope Mason and Robert Wokler (1992) excerpt and text search, with introduction
• Diderot, Denis. Thoughts on Religion (2002 edition) Translated and edited by Nicolas Walter. G.W. Foote & Co. Ltd. Freethinker's Classics No. 4. ISBN 978-1911578024.
• Main works of Diderot in English translation
• Hoyt, Nellie and Cassirer, Thomas. Encyclopedia, Selections: Diderot, D'Alembert, and a Society of Men of Letters. New York: Bobbs-Merrill Company, 1965. LCCN 65-26535. ISBN 0672604795.
• Kemp, Jonathan (ed). Diderot, Interpreter of Nature: Selected Writings. New York: International Publishers, 1963.