Professors of philosophy Janet Radcliffe-Richards and Derek Parfit. © Mark Allan

In the 1980s there was a seminar held regularly in the wood-panelled Old Library at All Souls College in Oxford. It was known informally as “Star Wars.” Four giants of moral and political philosophy would take turns to lead the discussion and spend the best part of two hours sparring with each other at one end of the room, which would be packed mostly with eager, awestruck postgraduate students. I was one of them and attended for a term.

The four philosophers were Derek Parfit, Amartya Sen, Ronald Dworkin and GA “Jerry” Cohen, all of them in their scholarly prime. In 1982, Janet Radcliffe-Richards, who had just moved to Oxford, decided to go along to see for herself what everyone agreed was the best show in town—dazzling, preening intellectual pyrotechnics. She was then in her late thirties, and a lecturer in philosophy at the Open University. She had recently published a book entitled The Sceptical Feminist.

Sen, who would go on to win a Nobel Prize in economics, already knew Radcliffe-Richards and after the seminar went over to greet her. “Who was that?” Parfit asked him. After extracting her name and being told that she had recently separated from a partner, Parfit wrote her a letter, which she says she will publish one day. “The most remarkable chat up letter in history,” Radcliffe-Richards calls it. He’d bought The Sceptical Feminist as, according to her, “a sort of audition” and proceeded to pursue her assiduously, oblivious to the fact that he was in competition with four other men.

Today, Parfit is considered by many of his peers to be the world’s most important living moral philosopher. His first book, Reasons and Persons, published in 1984, is routinely described as a work of genius. He is now married to Radcliffe-Richards, herself the author of three widely admired books characterised by unflinching logic and a willingness to tolerate uncomfortable conclusions. Not only are Parfit and Radcliffe-Richards arguably the world’s most cerebral romantic partnership, they are a fascinating study in the extent to which a philosopher’s professional convictions, particularly in the sphere of moral philosophy or ethics, shape his or her personal conduct—as Parfit thinks they should. I recently visited them in…

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