THERE ARE, at last count, the remains of 82 men and women housed in the marble crypt of the Panthéon, the neo-classical pile that has served, off and on, for the past two centuries as France’s Hall of Fame. Most French citizens, I suspect, can name perhaps a half-dozen of the marble basement’s inmates. Rising above — figuratively speaking — the brigades of forgotten generals and marshals are figures like Émile Zola and Alexandre Dumas, Simone Veil and Marie Curie, Jean Jaurès and Jean Moulin.

For a nation most often associated with the Enlightenment, however, philosophes are few and far between — or, in one case, not so far in between. The mausoleums of the Enlightenment’s most famous defender, Voltaire, and its most famous tormentor, Jean-Jacques Rousseau (who, for the record, was not French, but Genevan), are next to one another. That these two men, who utterly despised one another in life, became neighbors in death is an irony they both would have appreciated.

Interred a few years apart at the end of the 18th century, this odd couple was recently joined by their younger contemporary, the Marquis de Condorcet. A mathematician who also philosophized, the marquis remained resolutely optimistic about the ineluctable progress of humankind. Notch up another irony: Condorcet’s life ended in a prison of the revolutionary Terror.

Yet, the philosophe most deserving of the epithet “To great men, a grateful nation” — the gendered imperative above the entrance to the Panthéon — is nowhere to be seen. In fact, the bodily remains of this particular philosophe lie in anonymous indignity: in 1793, grave robbers ransacked the local church vault in which his body was buried and scattered his bones across the floor. Thrown into a cart by a cleanup crew, they were then dumped in a nearby mass grave.

The elusiveness of his remains mirrors the elusiveness of Denis Diderot’s character. Famed during his life as the editor of the age’s most famous work, the Encyclopédie, he became famous after his death as the author of the age’s most subversive (and often side-splitting) works of fiction and theory. He is the most modern of the Enlightenment thinkers, and the most maddeningly difficult to pin down.

There are a few excellent works in English on the life and writings of this extraordinary figure, most notably Arthur Wilson’s enormous biography and P. N. Furbank’s elegant study. Weighing in at 500 pages, Furbank’s book is nevertheless half the length of Wilson’s, but both have taken on wrinkles. Wilson’s tome was published in 1973, followed a quarter century later by Furbank’s. A new generation deserves a new Diderot, especially given the sharp relevance of his concerns and fierce honesty of his voice.

In Diderot and the Art of Thinking Freely, Andrew Curran has stepped up to the challenge. A French scholar who has written widely on Diderot, Curran offers a clear and compelling account of this magnificent but mercurial thinker. Though hobbled, like earlier biographers, by crucial gaps in the documentation of Diderot’s early years, Curran does an admirable job in fleshing out his subject’s youth. He rightly focuses on the tension between Diderot père and fils. A pillar of the community in their native city of Langres, the father actually had his rebellious son imprisoned at a Carmelite monastery in order to prevent him from marrying a poor laundress he had met while studying for the priesthood in Paris.

Not only did the young Diderot escape Langres, return to Paris, and marry — mostly to his regret — the laundress, but he also escaped the reach of the church. Quitting his ecclesiastical studies, then legal studies (which was the paternal Plan B), Diderot was asked what profession he did want to practice. “My gosh,” he replied: “Nothing, nothing at all. I like to study; I am very happy, very content. I don’t ask for anything else.” Needless to say, Diderot’s declaration — one that today’s parents, unfortunately, do not as often hear as they should — shocked his father, who concluded that his son had gone rogue and cut off his allowance.

In a sense, Diderot not only went rogue — throwing over not just his religious training, but his religious faith as well — but he remained rogue, politically and philosophically, for the rest of his life. He became an atheist while other Enlightenment thinkers, including Voltaire and Rousseau, held fast to their deist faith; he became a philosophical materialist though he never surrendered his faith in free will; he became editor of 18th-century France’s best-known work though he was often forced to edit and write in semi-clandestine fashion; and he wrote some of the most admired works of literature from the same age, though they were not published until long after his death; and he became a herald of republicanism while his peers still clung to enlightened monarchism.

With confidence and care, Curran traces Diderot’s breathtaking intellectual itinerary. He does a fine job in explaining why the Encyclopédie was so revolutionary — think of it as the 18th-century’s internet — and why, without Diderot’s unflagging commitment (he wrote some 5,000 of the entries), courage (he refused to move the operation to more clement climes, even though he lived under the threat of imprisonment), and cleverness (including the ploys used to undermine the orthodox entries he was forced to publish in its pages), the 28-volume work would never have seen the light of day. He also provides cogent and insightful accounts of some of Diderot’s own books, both those that were his and his alone, like D’Alembert’s Dream and The Nun, and those he wrote in collaboration with others, most notably the Abbé Raynal’s History of the Two Indies.

Importantly, Curran also portrays both Diderot’s most attractive and most annoying qualities. He was a loyal friend, though in certain cases — most notoriously, with Rousseau — loyalty curdled into animosity. He was a loving father, though he did need a few years to warm up to his one and only surviving child, Angélique. He was rightly hailed as the Age of Conversation’s greatest talker, which prevented him from being any age’s greatest listener. He was light-years ahead of his peers in grasping the countless obstacles and miserable inequities facing women, but he also was a serial cheater on his wife. Yet these inconsistencies and contradictions, especially in his writings, also make for Diderot’s greatness. His chief legacy, as Curran concludes, is “this cacophony of individual voices and ideas […] and his willingness to give a platform to the unthinkable and the uncomfortable, and to question all received authorities — be they religious, political, or societal.”

Inevitably, students of Diderot will take issue with certain claims and narrative choices made by Curran. While he treats D’Alembert’s Dream at great length, he spends relatively little time on Diderot’s most stunning (and hilarious) novel, Jacques the Fatalist and His Master, which Curran nevertheless recognizes as “the most joyful, lighthearted, and yet perhaps profound of Diderot’s books.” (He thus misses the chance to measure the influence on the novel of Laurence Sterne, whom Diderot met in Paris, and his Tristram Shandy.) While he does discuss Diderot’s last work, an apology for the life of Seneca, Curran does not develop the deepest reason for the book’s genesis: Diderot’s failed effort to mold Catherine the Great of Russia into the enlightened ruler he ardently wished for. Or, again, Curran mostly passes over Diderot’s most fascinating quirk as a writer: his habit of colonizing existing texts, ranging from those of the 3rd Earl of Shaftesbury and Ephraim Chambers to those of Admiral Bougainville and Abbé Raynal, and making them his own. Finally, the title is rather misleading. Perhaps hoping to capitalizing on their runaway best seller, Sarah Bakewell’s How to Live: Or A Life of Montaigne in One Question and Twenty Attempts at an Answer, Other Press promises something which the book does not really deliver. Whereas Bakewell succeeds, through a sustained give-and-take with Montaigne, to explore how to live, Curran does not really explore, or explain, how either Diderot or we can think freely.

But these are quibbles. Curran has not only colonized the primary and secondary sources, but also made them his own. His book is a worthy successor to those of Wilson and Furbank, and serves as a powerful reminder that Diderot’s rightful place is under the Panthéon’s dome — if only to annoy both Voltaire and Rousseau.

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Robert Zaretsky teaches in the Honors College at the University of Houston. He is the author of numerous books and articles on French intellectual history. His new book, Catherine & Diderot: An Empress, A Philosopher and the Fate of the Enlightenment, was published this winter by Harvard University Press.