Derek Parfit (1942–2017) is the most famous philosopher most people have never heard of.

Widely regarded as one of the greatest moral thinkers of the past hundred years, Parfit was anything but a public intellectual. Yet his ideas have shaped the way philosophers think about things that affect us all: equality, altruism, what we owe to future generations, and even what it means to be a person. In Parfit, David Edmonds presents the first biography of an intriguing, obsessive, and eccentric genius.

Believing that we should be less concerned with ourselves and more with the common good, Parfit dedicated himself to the pursuit of philosophical progress to an extraordinary degree.

He always wore gray trousers and a white shirt so as not to lose precious time picking out clothes, he varied his diet as little as possible, and he had only one serious non-philosophical interest: taking photos of Oxford, Venice, and St. Petersburg. In the latter half of his life, he single-mindedly devoted himself to a desperate attempt to rescue secular morality—morality without God—by arguing that it has an objective, rational basis.