Between Aristotle and Hegel, none of the major Western philosophers were married. Is abstract thinking, at its highest, incompatible with the messiness of everyday life? At the age of nineteen, Isaiah Berlin said he was ‘vowed to eternal celibacy’. Was there a connection between his sexual abstinence and his choice of analytical philosophy as a career? During World War II he fell in love with the gentile Patricia de Bendern; this frustrating affair coincided with Berlin’s shift from abstract logic to the history of ideas. In 1956 he took a Jewish bride, Aline Halban. His personal history reflects difficulties in choosing between endogamy and exogamy, Zionism and the diaspora, negative and positive liberty.