IT IS RARE ENOUGH FOR A MAJOR WORK BY A MAJOR philosopher to emerge posthumously. What makes the appearance of the fourth volume of Michel Foucault’s History of Sexuality so remarkable is not just the fact that this text of nearly 400 pages languished in a bank vault for more than 30 years after his death aged 57 in 1984. It is also the book’s seductive, not to say salacious, title: Les aveux de la chair, now superbly translated into English by Robert Hurley as Confessions of the Flesh (Penguin Classics, £25).

Given that Foucault died of Aids and a series of biographies have not disguised his promiscuity, readers might expect some kind of self-revelation, or at least a self-justification, in this valedictory volume from beyond the grave. If so, they will be disappointed. But this book does offer insights into its elusive author, even if that was not his intention. Like the Marquis de Sade, whom he revered as the patron saint of libertines, Foucault studied the Christian theologians only to conclude from their diabolical view of human nature “that God created most men simply with a view to crowding Hell”.

First, a word about the text. The editor, Frédéric Gros, tells us that Foucault wrote the manuscript between 1980 and 1982, delivered it to Gallimard, his publisher, but then delayed its publication in order to complete volumes 2 and 3 of his History of Sexuality, which deal with classical Greek and Latin ideas about sexual love. Foucault apparently stipulated that none of his work should be published posthumously, but as he left no will he cannot seriously have expected posterity to allow his magnum opus to remain incomplete.

Gros does not explain why Foucault’s heir, Daniel Defert, (“The Perverts”).