Philippa foot, who died Oct. 3, her 90th birthday, helped transform the field of moral philosophy. Carefully attending to the way we actually reason about what we should do, she joined her friends author Iris Murdoch and philosopher Elizabeth Anscombe in reviving the ancient Aristotelian tradition of virtue ethics. They cared not just about the consequences of a deed but about the character of the doer, and saw morality as intrinsically bound to the good life.
She had a knack for drypoint examples that drew out fine moral distinctions: in a famous 1967 paper, Foot conjured the driver of a runaway tram that will hit five men on the track unless he redirects it to another track and plows into just one. A vast philosophical literature was spawned by this "trolley problem."
Foot--a daughter of a British guards officer and a granddaughter of President Grover Cleveland--divided her career between UCLA and Somerville College, Oxford. She was also an active member of the charity Oxfam. She had long argued that reason, while it could help you recognize the right thing to do, didn't necessarily motivate you to do it: we are not conscripts in the army of duty, but volunteers. Certainly Philippa Foot was.
Appiah teaches philosophy at Princeton and is the author of The Honor Code: How Moral Revolutions Happen