In the summer of 1929, the two most brilliant philosophy students of the Ecole Normale sat by the Medici fountain in the Luxembourg Gardens in Paris. Simone de Beauvoir had been swotting up on Leibniz, hoping to impress her new friend, Jean-Paul Sartre. He was three years older than de Beauvoir and already had a fearsome reputation. He was known to be devising an austere philosophy based on the conviction that human beings must create their own meanings in a meaningless universe. He was also known to have attended the student ball in the nude and to have thrown up on his headmaster. That morning in the Luxembourg Gardens, she fell under his peculiar spell. He was charming, eloquent, funny and mesmerisingly ugly. Sartre listened to her pitiful notions of transcendent “goodness”, then spent three hours tearing her philosophy to shreds.

A few months later, he proposed to her. De Beauvoir reminded him that he had condemned marriage as “a despicable bourgeois institution”, and so Sartre offered a romantic compromise: they would sign a two-year, renewable “lease”, reserving the right to experience “contingent”affairs. She took his toad-like face in her hands, noting the smell of tobacco and patisserie, and covered it in kisses.

So began one of the most baffling relationships in the history of literature. Sartre's love letters were a bizarre blend of academic philosophy, romance and science fiction: “We are two consciousnesses melded into one, floating...between earth and sky, and two little robot bodies.” To de Beauvoir's chagrin, their bodies were often apart. They were assigned to teaching posts in different parts of France, and then Sartre was conscripted. He spent nine months as a prisoner of war. Even when they were together, the male “robot” did little to satisfy the desires that de Beauvoir described in such scandalous detail in Le deuxième sexe (1949). For her, sex was like the irresistible surge of the ocean; for Sartre, it was a surgical operation, “with a little - a very little - pleasure at the end”.

“Contingent” affairs filled the void. Carole Seymour-Jones charts the permutations of Sartre's not particularly erotic “harem” and de Beauvoir's lesbian and heterosexual entanglements with increasing distaste. Shortly before his death in 1980, Sartre was regularly visiting nine female admirers. De Beauvoir had “dangerous liaisons” with several adolescent women, some of whom she “shared” with Sartre. The two philosophers kept their vow to tell each other everything, and their love survived half a century of sexual jealousy and public notoriety. De Beauvoir's farewell to Sartre, in La cérémonie des adieux, is a moving tribute to their ferocious lucidity: “His death separates us; my death will not reunite us. This is how things are. It is enough that our lives were in harmony for so long.”

Sartre and de Beauvoir are difficult subjects for a biographer. Anyone who tries to capture minds of such unrelenting intelligence is bound to feel like one of Sartre's hapless lycée students. According to one of them, he would walk into the classroom, looking “nauseated”, then “glare at his pupils and, after a silence of 45 seconds, would roar, ‘All these faces, and not one single glimmer of intelligence!'.” Seymour-Jones, the biographer of Vivienne Eliot, has produced a readable account of their lives. Although she focuses on bedroom activities, she also gives a keyhole view of the novels, plays, essays, memoirs and political campaigns that made the unstaunchable pair the Voltaires and Victor Hugos of the 20th century.

So much was expected of Sartre, and he was so determined to question his own authority, that he had almost as many enemies as admirers. He rejected the philosophy - existentialism - to which he owed his fame and fortune. Having decided that philosophers should be politically engagés, Sartre and de Beauvoir lent their prestige to left-wing causes without always sharing their comrades' ideals. Their courageous volte-face were often seen as acts of betrayal and hypocrisy, but they can hardly be accused of opportunism. When they opposed the colonial war in Algeria and the use of torture by the French army, they narrowly escaped death at the hands of right-wing terrorists. The author takes a resolutely cynical view. She presents Sartre's opposition to the Algerian war as evidence of his “cowardice” and consequent need “to prove himself a hero”. His generosity, with time and money, to friends and beggars, is described as “extravagance” and “recklessness”. De Beauvoir's passionate relations with some of her devoted students are condemned as “child abuse”.

Sartre and de Beauvoir could certainly be manipulative and cruel, and some of their political activities now seem dangerously wrong-headed. Until the invasion of Czechoslovakia, Sartre allowed his abhorrence of American foreign policy to blind him to the gulags. Naively, he fell in love with the Russian woman who was sent to spy on him. Philosophers who try to change the world are prone to make mistakes. The problem is that many of these accusations are based on little more than innuendo. The idea, expressed by some of Sartre's posthumous enemies, that he “collaborated” with the Nazis is ludicrous. Writers who wanted to be heard had to compromise with the censor. A few, such as Sartre and Camus, managed to preserve their intellectual freedom. Even as a prisoner of war, Sartre wrote and directed a mischievous play about Palestinian resistance to the Roman occupiers. “Many whispered,” says Seymour-Jones, without citing a source, that the play ensured Sartre's release because it allowed the Nazis to claim that the prisoners “were royally entertained”.

The mendacious memoirs of Bianca Lamblin, a jilted lover of Sartre and de Beauvoir, seem to have provided some of the more far-fetched accusations. Lamblin was interviewed by Seymour-Jones and will be pleased by this biography. In the end, the two philosophers are reduced to a few spasmodic gestures and simple motives. When the ageing Sartre begins to spill his food in restaurants, Seymour-Jones comments, his “growing blindness was becoming an embarrassment, although not to him”. It is impossible to tell, from this account, why de Beauvoir spent half a century with such a monster and why 50,000 people followed his coffin to the grave.

A Dangerous Liaison: Simone de Beauvoir and Jean-Paul Sartre by Carole Seymour-Jones
Century £20 pp592

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