On the cusp of the Second World War, four women went to Oxford to begin their studies: a fiercely brilliant Catholic convert; a daughter of privilege longing to escape her stifling upbringing; an ardent Communist and aspiring novelist with a list of would-be lovers as long as her arm; and a quiet, messy lover of newts and mice who would become a great public intellectual of our time. They became lifelong friends. At the time, only a handful of women had ever made lives in philosophy. But w...