On September 1768, Diderot wrote a long and effusive letter to his friend the sculptor Etienne-Maurice Falconet, who was in Saint Petersburg, entrusted by Catherine II with the task of creating a bronze equestrian statue of Peter the Great. The letter was among the last in a long epistolary debate initiated in 1765, in which the two friends vigorously argued about the long-term survival of the artwork, as well as the artist’s and the philosopher’s desire for posthumous celebrity. In the following pages, I will take this letter as an entry point into a discussion of Diderot’s enduring preoccupation with posthumous fame, a concern that culminated some ten years after the exchange with Falconet in his last masterpiece, the tortuous, rambling and at times agonizingly personal Essai sur les règnes de Claude et de Néron. I intend to show that Diderot’s earlier optimism vis-à-vis his status in the Republic of Letters and his role as a public intellectual gave way to a profound identity crisis like the one that gripped his former friend Jean-Jacques Rousseau in his final years, documented in Rousseau juge de Jean-Jacques. By engaging both personally and by proxy in a battle against past and present enemies, Diderot forced himself to confront his own death and legacy, which he no longer imagined to be eulogies and loving praise, as he had in the letter to Falconet, but rather biased judgments of indifferent by-standers and prejudiced readers. In facing his eventual solitude as a writer, however, Diderot found comfort not among his contemporaries, but in the revived memory of the Republic of Letters’ classical past: in his newly discovered affinity for Seneca and in the embrace of his new role as Seneca’s advocate, faithful son, and alter ego.

In his letter to Falconet, Diderot addressed his friend’s care to preserve his reputation in the face of some damaging rumors that had been circulating at the Russian court. In a typically self-congratulatory mood, Diderot treated Falconet to a dose of his own wisdom:

I am in control of my own happiness and I challenge all the ingrates, scandalmongers, slanderers, envy-ridden scoundrels of the world to try taking it away from me. The world’s most powerful despot may rule over my life, my fortune, my freedom, but not over my honor and my reputation. I place the highest trust in virtue, talent and honesty; and until now, such trust has not been disappointed.[1]

To anybody familiar with the French world of letters, the slanderer, the mudslinger, the jaundiced scoundrel had a name: Rousseau. Formerly Diderot’s close friend, Rousseau had publicly and dramatically announced their break-up in print ten years earlier. Diderot had never used the printed medium to reply or retaliate. He now feels recompensed for having kept a dignified silence: “He knows that no matter what he may invent, concoct, devise, do, I will never entertain the public with the scandalous spectacle of two friends ripping each other apart. […] He knows that I will remain silent.”[2] In the well-ordered reality he presently inhabits, Diderot’s dignified stance has been amply rewarded with success and with the enjoyment of a vast network of friends. In the relative privacy of his correspondence, Diderot now allows himself to indulge in a delicious moment of Schadenfreude, by drawing a gratifying parallel between his own happy life and the miserable existence of the calamitous Rousseau:

I despise and I pity him. He is remorseful and shame pursues him. He is alone with himself. […] I am loved, esteemed, I’ll even say honored, by my fellow-citizens and by strangers. […] The benefits held out by the great empress extend far and wide her renown, the praise of her actions and of my own. The news come to the traitor’s ears: he bites his tongue with rage. His days are filled with sadness; his nights are restless. I sleep peacefully, while he grieves, perhaps he cries, tortures himself and wastes away.[3]

In this best of all possible worlds, truth is rewarded with celebrity, recognition and honor; virtue is championed by power; more precisely, by the power of the empress of Russia who, since 1765, has honored the philosophe with friendship, protection and material rewards. The empress’ support vindicates Diderot despite the wounds inflicted upon him by his peers in the Republic of Letters and the obdurate hostility of the French authorities. Diderot’s happy scenario recalls the old feudal tale of honor insulted and ultimately rewarded, with Rousseau in the role of the felonious baron, and Catherine the God-sent defender, who rescues the affronted Diderot on the stage of international opinion. Diderot adds: “Time brings virtue its champion; he may be close or far away; in a garret or on a throne; in Paris or in Saint-Petersburg, I don’t know: but he never fails to appear.”[4]

Let us leap forward ten years, to Diderot’s last great work, the Essai sur les règnes de Claude et de Néron, a first version of which was published in 1778. A much more complex scenario of this slandered authorial virtue is at play in this genre-bending, unclassifiable work, partly didactic and argumentative, and partly confessional and meditative. Some of the characters are still playing the same part, in particular Rousseau, who is once again the libelous villain; but others have dramatically switched roles: for example, Diderot has become a defender. Catherine, however, seems to have vanished from the scene. But has she? As we shall soon see, when she does make an appearance, her character and its function have undergone quite a transformation. Most importantly, the fantasy of vindication is no longer fulfilled: as ardently called for as ever, it may be postponed indefinitely, and may perhaps never occur.

The book had been conceived as an oeuvre de commande, but quickly absorbed all of Diderot’s energies, as had often happened with his projects. The late abbé La Grange (the tutor of the d’Holbach children) had completed a translation (the sixth French translation since the Renaissance) of the philosophical works of Seneca, at the request of the Baron d’Holbach, and Naigeon had asked Diderot to write a preface. A canonical work by an eclectic philosopher who united Stoicism and Epicureanism, a man of the vertu des païens, whose wealth, political choices, and exemplary death had been the object of an age-old debate, had been given the imprimatur of the coterie holbachique (the circle gathered around the Baron d’Holbach). Since authors from Tacitus to Cassius Dio, Montaigne to Justus Lipsius, and La Mothe Le Vayer to La Mettrie had weighed in on this debate, the publication was meant as a strike in favor of philosophical propaganda, another example of that extended dialogue with emblematic figures from the antiquity that had proved useful in fashioning the philosophes’ self-image.[5] The periodicals that were hostile to the philosophes responded as expected: the Essai sur la vie de Sénèque, as the book was initially entitled, was the target of a negative review in the newly founded daily Le Journal de Paris; the abbé de Fontenay wrote in a similar tone in Affiches, annonces et avis divers; and so did the abbé Royou in the Année littéraire, as well as the abbé Grosier in the Journal de littérature. The reviewers were unsympathetic both to the character of Seneca and to his philosophy, as well as to the “vile apologist” Diderot; the Année littéraire reproved the shady dealings of the “philosophical confraternity” that had sponsored the work. Diderot took a long time to reply. When he did, in 1782, the new version of the Essai had expanded tenfold: the commentary on Seneca now incorporated all of the critiques published in the various journals, which Diderot painstakingly refuted one-by-one.

The issue of monstrosity comes up several times in the text (the alleged monstrosity of Seneca’s conflicted life and the actual monstrosity of his own times), and the book itself is a sort of monster. In this vast exegetical hall of mirrors, the dead engage with the living in a dialogue beyond the grave in which they vent old and new resentments, as new accusations are piled upon old ones. “I speak to the dead as if they were alive, and to the living as if they were dead,” Diderot notes.[6] In reality, his book is a palimpsest which only the contemporary reader is able fully to decipher. To the first layer of his commentary of Seneca’s oeuvre, Diderot adds a second layer, his reply to various critics; a third layer is then superimposed, consisting of his colleague and ally Jean-François Marmontel’s rejoinder to those same critics, which Diderot annexes to his own; and a fourth layer consists of Diderot’s reply to Marmontel’s response. This saturation of exegetical fervor, which is dialogical overkill, makes the Republic of Letters into a republic of bickering. The vast dialogue of the dead is both ephemeral and eternal: two-thousand year-old accusations bequeathed by a venerable tradition in Latin and Greek are discussed in the same breath as recent criticism in short-lived journals that Diderot is the first to brand as perishable, their authors discounted as “our weekly aristarchs” (nos aristarques hebdomadaires, 1094). The book creates a vast echo chamber of guilt and innocence by association: the ancients and moderns who blame Seneca find themselves accused of standing on the wrong side of history, against all of Seneca’s admirers over the centuries, including Tacitus, Montaigne, Justus Lipsius, Marmontel, and of course, Diderot and the entire Enlightenment. Conversely, the game of philosophical partnership comes full circle, since criticizing Diderot amounts to disrespecting Tacitus, Montaigne et al.

Seneca had been controversial since antiquity; the debate over his character had cut across the ages, touching on the relationship between his character and his work, between philosophy and wealth, and between morality and politics.[7] Here was a stoic philosopher who had written eloquently about generosity and benevolence, yet had become fabulously rich thanks to his position as Nero’s favorite and also (reportedly) because of speeches against the populations subjected to Rome (he was said to have triggered a revolt among the Britons, driven to desperation by his usury).[8] He was a stoic who had extolled the virtues of a vita contemplativa, yet, in the Consolatio ad Polybium, had abjectly begged a courtier to be called back to Rome from Corsica, where he had been exiled on charges of adultery with Caligula’s sister. A pedagogue who had raised the young Nero and later abetted and covered up his crimes, in particular the murder of Nero’s mother Agrippina, he had eloquently eulogized the emperor Claudius while he was alive and mocked him mercilessly after his death.[9] Portraying Seneca as a righteous man is for Diderot a delicate task which involves selecting and parsing the various accounts that historians have left of his life, choosing among his works those that fit coherently within Diderot’s hagiographical project and rejecting as spurious those that don’t.

Several years after the publication of the Essai, the former protégé of Voltaire turned anti-philosophe Jean-François de la Harpe recalled the whole affair as an example of philosophical intolerance:

Fifteen or sixteen years ago, there was a great brouhaha about Seneca. […] The controversy mostly concerned his character and it became like a criminal trial, to the point that there never was a more violent, outrageous, fanatical brief [factum judiciaire] than the one Diderot wrote against a few journalists who, in their review of his translation of Seneca’s works [sic], had dared disapprove of his conduct or even raise the faintest shadow of a doubt about his virtue.[10]

La Harpe was incensed by the fact that one could not freely criticize an ancient philosopher without being incinerated by Diderot’s fiery eloquence. His plea in the name of academic freedom of speech was a little disingenuous, but he had a point. He added: “it is extravagant that one should not be allowed to criticize an ancient man, dead for the last seventeen hundred years, without hating truth, not even if this man were a Cato or Phocion the Good.”[11] Indeed, La Harpe’s characterization of Diderot’s work as a “factum judiciaire,” a legal brief in a criminal trial, was entirely accurate. Diderot had not produced a scholarly commentary but a brief in a judicial procedure; his writing makes ample use of invective, peroration, and prosopopeia, all the rhetorical tricks of the Ciceronian sublime. A brief entry in the Encyclopédie can help us explain the divergence between La Harpe’s conception of permissible critique and Diderot’s own use of the same: it concerns the difference between critique and censure. “Critique is employed in works of literature, while censure is employed in theological works, in doctrinal statements or in morals.”[12] In other words: critique is aimed at matters of taste; censure at moral conduct and belief. To Diderot, Seneca’s philosophical legacy is a moral exemplum and it is sacred. Thus, the critics of Seneca are not simply wrong, they are also evil. They do not limit themselves to erring in their understanding of the text: they also falsify the author’s work and his legacy and smear his good character. As such, they are contemptible and abject. For their sins, they must be ejected from the Republic of Letters and exposed to the disdain of future generations. Thus, the Greek-speaking Roman historian Cassius Dio, the author of a Roman History, is charged with an “incurable perversity of judgment and morals,” having practiced “the vile trade of schemer, courtier and flatterer,” and the eleventh-century Byzantine monk Joannes Xiphilinus, Cassius’s epitomator, or abridger, is “a kind of madman, an evil man, a grotesque mind.”[13] The seventeenth-century moralist and Epicurean libertine Saint-Evremond is a “ridiculous” and “frivolous old man,” “a scurrilous pontificator,” wallowing in the “rubbish of letters.”[14] It is as if, in the fervency of his denunciation, Diderot were following in the footsteps of Rousseau in his Dialogues de Rousseau juge de Jean-Jacques, of which Diderot had just read the first Dialogue, published in 1780. Diderot, much like Rousseau, casts his critics as enemies and brands them as enemies of humanity by conflating his hero and himself with suffering humanity at its highest, as well as with ultimate innocence and goodness (Seneca having replaced Socrates as the epitome of the martyred philosopher).

Indeed, the figure of Rousseau is at the core of Diderot’s last work. That is not so much because—contrary to his (previously stated) better judgment—Diderot finally settles his scores publicly with Rousseau, but also because, in this obsessive, painful and tortuous meditation on Seneca’s legacy and by extension on his own, Diderot engages in a confrontation with his public image and with posterity that is saturated with the ethos of Rousseau, in particular with that of the Dialogues de Rousseau juge de Jean-Jacques. Both works take a circuitous path to autobiography, borrowing the judicial structure of a cause célèbre: what is at stake is the moral character of the author, his guilt or innocence. To put it differently, both texts ask both “what does the life of an author tell us about his work?” and conversely “what does the work tell us about its author’s life?” In Diderot’s portrait of Seneca this relationship is circular: the life of the author is used as a critical tool to evaluate his works, to embrace those that seem to reflect and enhance it and to reject as inauthentic those that don’t cohere with the portrait Diderot draws of him. Likewise, the authority of the work is invoked in order to validate those actions that reflect its spirit and to reject as false those that seem to contradict it. As if, however, to counteract such yearning towards unity, both Rousseau’s and Diderot’s works display disarticulation, a split in the authorial persona that nonetheless does not prevent the author’s voice from exerting a powerful impact on the reader. It is as if the broken, dissonant fragments of the author’s identity came together only in the act of addressing an audience, no matter how prejudiced, unsympathetic, or even (in the case of Rousseau) non-existent that audience is. We know that in the Dialogues Rousseau explores in painstaking detail the plot enacted against him by the “philosophical sect,” the existence of which is never in doubt; like a secret society or a state within the state, the sect has infiltrated the social fabric, corrupted the mechanisms of public opinion and turned it against Rousseau, who now passes for a criminal in the eyes of a malevolent nation, although his crime remains unknown to him, and his indictment has never been publicly spelled out. Rousseau and Diderot bequeath their personal animosity to the future, yet they are remarkably similar in their concern for their posthumous character, and in their desperate attempt to exert some control over it even after their death.

As Antoine Lilti has recently argued, Rousseau’s paranoia is not so much an issue of psychiatry as of social history, for it reveals the contradictions inherent to the new status enjoyed by consecrated writers.[15] There is a dark side to celebrity, for Rousseau no longer recognizes himself in his public image: hence his obsession with his own monstrosity in eyes of others. He is now “the most hateful of all monsters and the horror of the human species.”[16] Celebrity has led the public to fabricate a false image of Rousseau and has thereby dispossessed him of his true self. The last years of his life were spent in the thick of urban Paris, among the crowds of les Halles, where a constant stream of visitors brought him not comfort, but further alienation: “They have found a way of turning Paris into a wilderness more awful than caves and forests; he finds among men neither communication, nor advice, nor understanding. […] If he enters a public space, he is looked upon as if he were plague-stricken; everyone surrounds him and stares, in silence and keeps his distance.”[17] Forever the object of curiosity, Rousseau feels that he lives in a glass house, constantly exposed to public scrutiny and consistently betrayed by it. Such intimacy with the Parisian public has paradoxically resulted in his complete solitude. Public opinion has fabricated a monster which has taken the place of the real Rousseau. This specter appears most plainly in the description of a popular festivity, the burning of a Swiss straw man that is paraded under his window: “To this purpose, they lent his shape and dress to a straw man, they armed it with a gleaming knife and, parading it with ceremony through the streets of Paris, they were careful to station it directly under the windows of J. J.”[18] Rousseau portrays the plot against Jean-Jacques as a counter-Enlightenment, a world of shadows and illusions in which public opinion, rather than being an autonomous entity devoted to spreading true knowledge, has willingly turned itself into the docile instrument of the plot enacted by the secte philosophique.

Diderot no less bitterly expresses the paradox of the celebrated author’s betrayal at the hands of his most devoted public, although he narrates it less dramatically. Neither Diderot nor Rousseau have much faith in public opinion: both see it as credulous or perversely easy to manipulate. The Dialogues and the Essai evoke a world in which individuals cannot endure being alone, but are eager to make themselves subservient to the opinion of the majority, regardless of what evidence and reality tell them: “Once the spin is set in motion, each and everyone follows the current and increases its force. How can one mistrust one’s own opinion when one sees that it is shared by everybody else?”[19] “The public is deceived, I see it and I am aware of it; yet it enjoys being deceived and does not want to be disabused.”[20] Diderot, for his part, also gives voice to resentment of the public’s credulity: “Was there a limit to the public’s credulity? Enemy of men of genius and even more offended by men of virtue, it did not discuss the accusations thrown at Seneca: does the populace ever discuss? It believed evil the same way as it would today; it is malicious and, to an even greater extent, stupid.”[21] “The man of the people is the stupidest and meanest of men: to depopularize oneself, or to better oneself, are one and the same thing.”[22]

At the end of their lives, both Rousseau and Diderot felt alienated from the readership they had sought to edify and seduce. They seemed to come to the realization that the very values upon which they had pinned their hopes of posthumous glory—that is, their eloquence and their philosophical personae—had become sources of resentment on the public’s part, for the public could not tolerate feeling inferior to men of genius. No longer straining to hear the “the imperceptible sounds of the far-away concert” emanating from “the countless crowd of admirers which alone can satisfy a spirit yearning for the infinite” (the admirers that Diderot had fantasized about in a letter to Falconet),[23] he became convinced that the philosophe and his public were locked in a struggle for mutual recognition whose end was forever postponed. In his admirable analysis of the implications of Rousseau and Diderot’s quarrel with public opinion in their last works, Yves Citton notes that Diderot’s earlier faith in the philosophe’s ability to guide public opinion had been shattered by the time he confronted Seneca’s fate and his own in the Essai. In 1766 Diderot had reassured Falconet that all would be well in a world that accepted being secretly led by the benevolent authority of the philosophe:

When I talk about public opinion I don’t mean the motley crowds that clamor in the pit and hoot a masterpiece, kick the dust at the Salon, and look for their opinion in the reviews. I am talking about that small flock, that invisible church which listens, observes, meditates, and speaks in muted tones, but whose voice prevails in the long run and shapes public opinion. I talk about the sound and thoughtful judgment of an entire nation; a judgment that never falters, is never ignored, which remains when all the other small, individual interests have waned.[24]

But in the Essai the select flock of philosophical friends is no longer able to sway public opinion in its abstruse but effective ways. Some of the old companions (such as Grimm and Falconet) have withdrawn, but most importantly, Diderot has lost faith in the existence of secret affinities between the masses and the philosophical cohort: the philosophe is now left alone to confront the multitude, and the celestial choir of posterity has turned to the invectives of today’s lynching mob. “All the trust that Diderot had placed in the public recognition of his merits had rested on the workings of the ‘secret church’ from which a sound judgment would issue,” notes Citton; but “all it would take to turn that atheist’s paradise into hell would be for his faith in that church to be shaken.” Rousseau, who had always seen the philosophical church as a malevolent secret society entirely devoted to his personal destruction, had been living in that hell for a long time.[25]

Despite those misgivings, both Rousseau and Diderot fight on the edge of the grave in order to restore their reputation. “I would easily resign myself to disappearing from human memory, but I confess that I cannot bear to remain in it defamed. [...] I cannot consider the restoration of my memory and the recovery of the esteem due to me a matter of indifference to men,” writes Rousseau.[26] Despite his complete disenchantment with his contemporary readership, Rousseau still places some faith in posterity. It is because he somehow hopes to reach out to future generations that he multiplies the manuscripts of the Dialogues and attempts to deposit them in safe hands.[27]

Diderot had pursued an authorial strategy different from Rousseau’s, for his early skirmishes with the authorities had dissuaded him from publishing most of his works: his relationship with the reading public had been limited mostly to his role as editor of the Encyclopédie and to his connections with Catherine of Russia. Hence Diderot was enormously invested in his posthumous existence as an author, the only hope he had of seeing his long-deferred promise fulfilled. “Indeed, posterity would truly be ungrateful if it forgot me completely, given that I have been thinking about it so much.”[28] It is therefore not surprising that the travails of Seneca’s personal and literary celebrity would be treated on a par with his own: indeed, the two merged, since—notwithstanding his claim to be nothing but the handmaid of Seneca’s text—Diderot appropriated, even cannibalized, Seneca’s work. Such convergence between the identities of an ancient philosopher and a living author makes perfect sense when we consider that Diderot loved contemplating himself through the telescope of posterity, that that he enjoyed nothing more than projecting himself towards virtual cheering crowds located as far into the future as possible. Diderot’s mind is the stage on which a never-ending Dialogue of the Dead is continuously unfolding for the edification of the Brave New Reader: hence his notion that he shares with Seneca the timeless monumentality of philosophical fame.

Yet there was a flip side to the cult of great men that Rousseau and Diderot so passionately endorsed: it was the anxiety of defamation, the fear that their legacy would be forever disfigured and their work falsified. Why was this so? Perhaps we may find an answer by interrogating a belief inherent in the self-sacrificial, militant, and didactic conception of philosophy which they embraced: that the true measure of success was persecution and hostility and not the admiration of crowds. “This book would be very mediocre if it did not manage to arouse hatred and raise the clamor of wickedness,” Diderot observes in the Essai. A few lines earlier he asks: “What is the purpose of philosophy if not speaking up? Speak up or relinquish the title of pedagogue of humankind. You will be persecuted; that is your destiny. They will make you drink hemlock; Socrates drank it before you. Drop your magisterial robe or forsake your tranquility: your state is a state of war.”[29]

This was very much Rousseau’s stance too. It may be argued that Rousseau was able to stick to his magisterial, Socratic role to the very end, and that he had found his own kind of hemlock in the symbolic death sentence that the conspiracy inflicted upon him. His embrace of the philosopher’s war with society meant that he spent the last years of his life haunted by the thought of society turning against him, driven to hate him out of a feeling of resentment against the philosopher-benefactor’s unquestionable superiority: “‘Don’t you see that this contempt that they flaunt is not real, that it is nothing but the transparent veil of an admiration that distresses them and of a rage that they cannot disguise?’” the character named “Rousseau” declares in the Dialogues.[30] But things were different with Diderot. In 1749, while he was imprisoned at Vincennes and following the publication of the Lettre sur les aveugles and Les bijoux indiscrets, he devoted his time to translating Socrates’s Apology. But the next apology he was able to write was the one he sent to the lieutenant general of the police, Monsieur Berryer, in which he recanted his work, gave away the name of his publisher, his bookseller, and that of his mistress and partner in crime, the writer Mme de Puisieux. Diderot was painfully aware that in his own life he had not been quite capable of rising up to his glorious ideal of philosopher. Besides, the role of Socrates had already been taken by Rousseau, as most people agreed. Diderot’s Seneca was thus a pis-aller, a makeshift role model appropriate to a tainted philosopher who had several times bowed to necessity, played the game, and recanted his ideas.

Yet, as he pours his soul into the task, Diderot turns his reading of Seneca into an example of filial piety and unabashed self-promotion. Revisiting and absolving the sins of the son and redeeming the father are moral duties, tasks fiercely and doggedly carried out. There are many parallels and similarities between his own times and those of Seneca: imperial Rome recalls Parisian decadence; Nero has something of Frederic II or Louis XV; “Seneca’s detractors bear a striking resemblance to those of the philosophes.”[31] One Suillius (souillé), a man who had accused Seneca of corruption and political fraud, and whom Diderot describes as a “venal and fearsome informer, a scoundrel rightly abhorred by all the citizens […] a madman sullied, indicted, punished with a thousand crimes,”[32] is explicitly compared to Rousseau, who is himself a hypocritical scoundrel […] a heinous man,” a “monster,” the author of a posthumous, “revolting pamphlet” (the Confessions), whose seductive and slanderous voice, resounding from the grave, will forever enjoy the last word.[33] This time, however, no powerful, royal champion rises to restore the truth: Catherine no longer appears as the great empress, the guarantor of Diderot’s glory. Refracted through the mirror of history, she has morphed into a petrifying creature, half-Nero, half-Agrippina: her company can only bring dishonor to the philosophe. Following Agrippina’s example, Catherine has murdered her husband, Peter III, in order to win power; like Agrippina, she has used the services of a respected philosopher in order to refurbish her image in the eyes of public opinion. “Agrippina, eager to become famous for something other than her crimes, requested Seneca’s recall. [...] She was hoping to please the people, who had a high opinion of the talents and wisdom of that philosopher.”[34]

In revisiting the dubious position of Seneca in those circumstances, Diderot had not forgotten his own role as Catherine’s grateful protégé, de facto publicist and advocate before the European public, in particular the shady part he had played in the Rulhière affair. Claude-Carloman de Rulhière was the former secretary to the French ambassador in Saint-Petersburg and the author of a manuscript Histoire de la révolution de Russie that narrated the events of Catherine’s accession to power, the murder of her husband, and its awkward cover-up; it was also very unfavorable to her government. In 1768 Diderot, at the suggestion of the empress, had gone to great lengths and had concocted elaborate schemes in order to discredit and smear its author in Parisian circles.[35] Fourteen years later, in the Esssai, he intimated that he had not forgotten him. Rulhière had compared Catherine’s court to that of Nero, as described by Tacitus. Diderot could never be as explicit: but his choice of metaphors in the Essai suggested as much. Nero, he wrote, was a “tiger gone mad” and his court was “the pit of a tiger’s lair.”[36] That was not the first time he had used such a metaphor to describe an absolute tyrant. In 1774, when he was on his way back from Russia, at a time when gratitude compelled him to publicly extol the virtues of the empress, Diderot had written from the Hague to Mme Necker: “I will confess to you in a hushed voice, that those among our philosophes who seem to have known despotism the best, have only seen it through the neck of a bottle. What a difference between a tiger painted by Oudry and the real tiger in the forest!”[37]

The scenario is thus very different from the one sketched in his letter to Falconet fourteen years earlier. At that time, Catherine’s former mentor had anticipated that his friendship with the empress would rescue him from the squabbles of the Republic of letters and from Rousseau’s attacks. Now, in the Essai, Diderot confronts the failure of such an illusion, the collapse of the partnership of Enlightenment with power. In a significant moment of critical introspection, thanks to the mediating figure of Seneca, Diderot is able to reflect on his own, once intimate relationship with the tyrant: “Once they become corrupt, the powerful no longer question their actions […] and when we do not debase ourselves for them as much as they would like, they accuse us of ingratitude. In the midst of a corrupt court, the man who accepts or solicits benefits is not aware of the price he’ll have to pay one day. That day he will find himself caught between sacrificing his duty, his honor, and neglecting the benefit; between contempt for himself and hatred for his benefactor.”[38]

At the end of their lives, their youthful certainties of public recognition in disarray, Rousseau and Diderot addressed the contemporary audience as if it were a virtual one; they spoke to it, as it were, from the grave: “We cannot think, we cannot speak forcefully anywhere but from the grave,” Diderot declared; “that is where we must be; only from there can we address humankind.”[39] Transcending his last, mournful, acrid declaration of friendship lost and betrayed, Diderot engaged in a kind of debate with his former friend. Like Rousseau, he issued an open-ended, unsolvable question and a plea for the inner coherence, the ethical unity, of life and work. Such an appeal flew in the face of the skepticism that Diderot had often voiced (notably in Le neveu de Rameau and the Salon of 1767) about the ethical status of genius: perhaps the virtues emanating from the artwork did not necessarily reflect those of its author: “I am well aware that the wisdom of one’s words does not prove the purity of one’s motives and that a perverse man may write and speak as eloquently about virtue as a good man,” he wrote in the Essai, obviously with Rousseau in mind.[40] Yet, in his last work, Diderot borrowed from his erstwhile adversary the same tormented interrogation, with which he ended: what would be the point of a philosophy that remained unsubstantiated by the philosopher’s life?[41]