The Marquis de Condorcet (1743-94) was a founding father of social science. He believed that what he called the moral sciences could be studied by the same exacting methods as the natural sciences, and he developed many of the tools for doing so. Condorcet has had two quite unconnected reputations: as the doomed and foolish Enlightenment scholar, writing about the perfectibility of mankind while in hiding from the Terror that would shortly claim his own life; and as the incomprehensible founder of social choice, whose Essai of 1785 was not understood until the 1950s. This book shows that he was not so foolish, nor so incomprehensible, as even sympathetic treatments have made him sound. A long introduction uses the latest French and English sources to put his work into context, explains the unity of his thought and explicates his difficult arguments in probability theory and social choice. The extracts from Condorcet's work that follow are in two parts. Part I, 'The Theory of Voting', includes some extracts from the notorious Essai of 1785 but also later work which is more accessible and makes new points. Part II, 'Human Rights', shows Condorcet the passionate campaigner for rights for slaves and for women, and the American constitutionalist. His poignant 'Advice to his daughter' and 'Testament' show the spirit of a man who knew he was almost certain to be killed, and would never see his daughter again. Most of the works translated here have never appeared in English before. They will be an essential reference source for everybody working in social choice, the history of mathematics and human rights, and the Enlightenment.