Includes bibliographical references and index.

Derek Parfit (1942-2017) is the most famous philosopher you've likely never heard of. In 1984, Parfit published what was, and is still, hailed by many philosophers as a work of genius - one of the most cited works of philosophy since World War II, Reasons and Persons. At its core, he argued that we should be concerned less with our own interests and more with the common good. His book brims with brilliant argumentative detail and stunningly inventive thought experiments that challenged contemporary views about what it means to be a person, why one should forego concern for oneself as an identity that persists over time, what it means to act on the basis of reasons, and what we owe to future generations. Parfit also - unfashionably at the time - believed in a kind of grand unified theory of morality, what he called theory x, a non-religious ethical theory wherein all the major moral theories were converging from different sides on the same mountaintop. Parfit has had an enormous influence not only on philosophy, but also beyond, particularly amongst those in the fields of climate ethics, poverty relief, and charitable giving. In this book, the first-full scale biography of Parfit, Dave Edmonds tells the story of the thinker that many philosophers consider the most important moral philosopher of the last century. Edmonds' rendering of the man in full skilfully illuminates the person behind the acclaimed philosopher. Despite Parfit's extraordinary mind, outward appearances suggest his was also an extraordinarily uneventful life - one largely spent in cloistered institutions from Eton to Oxford and one seemingly monomaniacally devoted to ideas. Edmonds' aim is to show how this son and grandson of missionaries went from a genial and outgoing history student to a captivating, yet monkish philosopher singularly devoted to saving morality. In doing so, Edmonds makes Parfit's profound, but often impenetrable, ideas accessible to a broad audience and gives life and body to the thoughts of a seemingly pure thinker that captured the imagination of a generation of philosophers.