The French philosopher Michel Foucault expressly forbade any posthumous publications of his work. “Don’t pull the Max Brod-Kafka trick on me,’” he reportedly told his friends. (Kafka’s friend Max Brod defied the author’s wishes by posthumously publishing his novels, including The Trial and The Castle.)

Thirty-four years after his death, Foucault’s wishes have been expressly denied with the publication of his fourth book on sexuality. Confessions of the Flesh, published last week in France by Gallimard, is the last in his History of Sexuality series. And, though incomplete, it’s a valuable addition to his oeuvre.

“For those of us who are interested in Foucault’s work, this is a proper book,” says Stuart Elden, political-theory professor at Warwick University in Coventry, England, and author of Foucault’s Last Decade. “This book is really the thing that holds the whole series together.”

The first volume in Foucault’s History of Sexuality series, The Will to Knowledge, was published in 1976 and explored contemporary attitudes towards sexuality. Elden says Foucault then immediately began researching the topic of what would become Confessions of the Flesh: Christian sexuality. But Foucault then decided he had to go back even further, and to hold off publishing his research on Christianity until he’d completed his work on pagan sexuality, which became volumes two (The Use of Pleasures) and three (The Care of the Self) in the series.

Confessions of the Flesh, says Elden, “gives us the reason [Foucault] felt he had to go to pagan antiquity to answer some of the questions he’s interested in. For me, it pulls the whole series together. Before, it was not very easy to see a connection between volume one and volumes two and three.” The posthumous fourth volume explores how early Christian thinkers used the notion of the flesh to conceptualize the relationships between the body, pleasure, and desire, says Elden. The book also examines how Christian thinkers in the 2nd to 5th centuries conceived of sexual relations within marriage. “He’s interested in the way that a wider range of sexual possibilities for the adult male in antiquity become narrower to just sex in marriage for procreation under Christianity,” notes Elden. But in Confessions of the Flesh, Foucault stresses that early Christianity is neither homogenous nor repressive, and highlights debates among Church fathers about whether and how sex should be restricted within marriage.

In 2013, Foucault’s papers—including unpublished material—were sold to the Bibliotheque Nationale in Paris, which made them accessible to researchers. Elden believes this may have sparked the decision to publish Foucault’s latest work as a whole, rather than allowing fragments to leak out. The style of the resulting book is historical and fairly austere, much like volumes two and three of the History of Sexuality series, which sets the first (and most well-known) volume as the most literary of the series. Confessions of the Flesh is not fully complete—there are missing references, and there are sections at the end that Foucault intended to be included in the book, but did not indicate precisely where they should be placed—but it is a detailed and substantive piece of work.

Eventually, the book will be published around the world, but as of now there is no definitive timeline. Gallimard said international publishers of the first three books in the History of Sexuality series will have bidding priority for the fourth volume.

Confessions of the Flesh may not shed new light on our current conception of sexuality, but it can help us understand our past. “Foucault is clear with his material on Pagan antiquity, the Greek and Roman thinkers, that you can’t find a solution to a contemporary problem in the historical past,” says Elden. “But he does use history to explain how we got to our present.”