Sontag: Her Life says she wrote Freud: The Mind of the Moralist by Philip Rieff, whom she married at 17

A new biography of Susan Sontag is set to claim that the American writer was the true author of her first husband Philip Rieff’s seminal work Freud: The Mind of the Moralist.

Out in September, Sontag: Her Life by Benjamin Moser lays out textual and anecdotal evidence that Sontag was not only the unofficial co-author of the 1959 analysis of Freud, which has long been known. Then in her 20s, the celebrated writer and filmmaker collaborated on the book with the sociologist Rieff, whom she married at the age of 17, just 10 days after attending one of his lectures.

Earlier editions of the 1959 book credit her – as Susan Rieff – with “special thanks” in the preface, but by 1961 any acknowledgement of Sontag had been dropped. According to Susan Sontag: An Annotated Bibliography, their 1959 divorce settlement stipulated she agree to Rieff’s claim of sole authorship.

While writing Sontag: Her Life, Moser was given permission by her estate to study the parts of her archive at UCLA that are off limits to the public for the next few decades, and also spoke to friends and acquaintances who had not previously opened up about their relationships with the writer.

Moser acknowledges in the biography that Freud: The Mind of the Moralist is based, at least to some degree, on Rieff’s research and notes, but claims: “He almost certainly did not actually write the book upon which his career was based.” Sontag’s friend Minda Rae Amiran told him that, while the pair lived in Cambridge, Massachusetts, “Susan was spending every afternoon rewriting the whole thing from scratch”.

Sontag’s diaries record how, in August 1957, she “continued to sort Freud materials, made notes, worked on some rough passages in Ch. 2”.

Moser quotes a letter Sontag wrote to her mother, in which she says that she is “in third gear now on the book – working about 10 hours a day on it at least”. And, in a letter to the author from her friend Jacob Taubes in 1958, he asks: “Did you, by the way, relinquish all rights on the Freud? It would be a crime.” When she says that she has, he replies: “I am without consolation … You cannot give your intellectual contribution to another person … It could be the ruin of Philip if he dared to come out shamelessly without your signature.”

According to Moser, who is also the author of a biography of Clarice Lispector, 40 years later Rieff sent a package to Sontag containing a copy of the book, inscribed with the lines: “Susan, Love of my life, mother of my son, co-author of this book: forgive me. Please. Philip.” Rieff died in 2006.

In a statement to the Guardian, Moser said: “It had long been rumoured that Susan Sontag was the true author of her husband’s great book, Freud: The Mind of the Moralist. She married Philip Rieff when she was just 17; in the pictures she looks even younger. And the book is so sophisticated that it hardly seemed possible that she could be the true author. But in the course of my research, I discovered that she had indeed written it, only agreeing to sign it over during an acrimonious divorce, in order to keep her ex-husband from taking her child. ‘It was a blood sacrifice,’ a friend told me.”

When Freud: The Mind of the Moralist was first published, the Guardian hailed it as “an event to be acclaimed … a book of genuine brilliance on Freud’s cultural importance … a permanently valuable contribution to the human sciences”. Scientific American, meanwhile, noted: “Rieff’s tremendous scholarship and rich reflections fill his pages with memorable treasures.”

After Sontag divorced Rieff, her career took off. Her first collection of essays, Against Interpretation, was published in 1966, followed three years later by Styles of Radical Will.

An Annotated Bibliography notes that “topics defining of Sontag’s intellectual itinerary” are evident throughout the book, “as can be gleaned from chapter titles alone: The Hidden Self, The Tactics of Interpretation, The Authority of the Past”. Readers “will likely hear Sontag’s voice as part of the book’s conversation with itself and its sources, via references (for example) to William Empson and Kenneth Burke, to Proust and Shakespeare and Mann, to Nietzsche and Goethe, etc.”

Sontag: Her Life is based on hundreds of interviews with people who knew her well, including the photographer Annie Leibovitz, said publisher Allen Lane, which releases the book on 17 September. Stephen Fry has called it a “monumental” biography that “reveals the surprisingly tender, insecure, simple and intellectually dedicated story of one the most remarkable literary figures to emerge in 20th-century America”.