In the 2002 biographical documentary on Jacques Derrida the director Amy Ziering Kofman asks the philosopher what he would most like to see in a film about Kant, Hegel or Heidegger. Derrida takes his time before answering. Then he responds: “their sex lives”.

Kofman is taken aback. “Why?” she asks. Derrida explains that these philosophers never speak about their own sex lives in their philosophy. They present themselves as asexual. But, he wonders, what could be more important to them and to their writing than love, those they love, and the making of love? Philosophy has a lot to say about love in general; perhaps philosophy even began with this question: what is love? And yet, according to Derrida, individual philosophers have little to say about their own love lives, at least in their philosophical texts. Philosophy concerns the depersonalised construction of logical and universal systems of thought. Traditionally there should be no room in it for biographical introspection about one’s own love life. However, the more one looks into the canon of philosophy the more it becomes apparent that in fact philosophers have had a great deal to say about their own sexuality.

The writing of Plato and Aristotle is replete with references to Greek love. The relations between characters in these texts are not always, shall we say, Platonic. Theologian and philosopher St Augustine of Hippo founded the confessional genre in writing. He writes of his pre-celibate days as a lover of many women, asking of God: “give me chastity and continence, but not yet”. The story of the medieval scholar Peter Abelard and his equally philosophical lover, Héloïse d'Argenteuil, is well known. Their love letters are one of the great epistolary exchanges in the western canon and Abelard’s love poems were at least as influential in his lifetime as his extensive philosophical writing. Jean-Jacques Rousseau makes reference to this in his own epistolary novel Julie, or the New Heloise. Like much of Rousseau the novel is a mix of fiction and philosophical reflection. In his own Confessions Rousseau tells us about his loves and losses, including Madame de Warrens, for whom he served as steward to her household and lover. Rousseau, like Kant after him, has a surprising amount to say about masturbation. Kant offers a treatise on conjugal rights and is quite stiff on the vice of self-love.

Other prominent examples include: Soren Kierkegaard’s The Seducer’s Diary – a tale of the seduction and manipulation of young women, easily read as a reflection on his own relationship with Regine Olsen; Diderot’s erotic La Religieuse (The Nun); and Schopenhauer’s treatise, On Women, which is hard to read as anything other than a reflection on his own experiences as male philosopher divided between scholarly independence, a desire for domestic contentment and eighteenth-century misogyny. Hegel, meanwhile, has much to say, philosophical and censorial, about the Christian family, marriage, and human sexuality, if seemingly not his own. He reserves that speculation for his letters to his sister and others, some of which were destroyed by his sons to prevent “misunderstandings” concerning his fathering of an illegitimate child with his landlord’s wife.

In the twentieth century we can find Heidegger occupied with the topic of ‘Care’ in his philosophy but reserving reflection on his affair with his student Hannah Arendt for their now published correspondence, another philosophical relationship that has also been subsequently novelised. Ironically, Arendt’s thesis that she wrote ‘under Heidegger’ was on Augustine and love. Jean-Paul Sartre and Simone de Beauvoir have quite a lot to say about their own love lives and not just with each other. Like Camus, such references often take the form of fiction. Roland Barthes’ most successful publication was A Lover’s Discourse, which can be read alongside his posthumously published account of his own sexual encounters in Incidents.

But it is probably Michel Foucault who is the great philosopher of sex, writing a three-volume history of sexuality before he died of Aids in 1984. However, unlike Derrida who makes his own biographical desires and sexual experiences central to a philosophical text like The Post Card, Foucault does not reflect in his published writing on his own “philosophy of the bedroom”, to borrow a phrase from de Sade.

It is not difficult to find through out the history of thought references to the sex lives of philosophers. The question is: how can identifying these moments help us to understand the philosophical text? I do not think that it is possible to suggest, as Niall Ferguson recently did of Maynard Keynes, that sexuality explains thought. That would be a reductive and extremely ‘un-philosophical’ thing to say. Rather, we might note that often the incidences of philosophers like Kierkegaard, de Beauvoir, or Derrida making a theme of their own sexuality occur at the borders of philosophy in the displaced form of literature.

Literature opens up philosophy and refuses to permit it to settle on what is and what is not allowable as philosophy. This is no accident, since the question of the sex lives of the philosophers is really one of what is permissible and what is not in a philosophical text. It is, in other words, the very question of what is philosophy. I do not think the issue of an author’s sexuality will provide us with an answer to this question, but it will allow us to ask it again and again, in order to affirm its complexities and contradictions as a condition of continuing to read philosophy today.