Philippa Foot, pictured in 1943

Philippa Foot, who died on 3rd October 2010 on her ninetieth birthday, was one of the outstanding moral philosophers of the post-war period. One of her best-known papers introduced what’s now known as “the trolley problem” into the bloodstream of philosophy (for more on this, see David Edmonds’ article in this month’s Prospect). But she later described her work in the field of “applied ethics” (thinking about ethics in real-life scenarios) as occupying her only while she searched for ways to approach the foundational questions in ethics—questions like why should we be moral at all.

Though her first paper in moral philosophy was published in the 1950s, and a number of her subsequent papers became landmarks in the literature, her one book, Natural Goodness, did not appear till 2001. The introduction quotes  approvingly Wittgenstein’s remark that in philosophy it is difficult to work