T. M. Scanlon, the Alford Professor of Natural Religion, Moral Philosophy, and Civil Polity at Harvard University, is one of the most important moral philosophers of the last fifty years. His development of contractualism, essentially a theory of “what we owe to each other,” has been widely influential in the fields of ethics, political philosophy, and social philosophy. Scanlon has published over 60 articles and chapters, and his books What We Owe to Each Other, Moral Dimensions, and the Difficulty of Tolerance have been hailed as seminal works in the fields of moral and political philosophy. He has been awarded numerous grants and fellowships, including the Guggenheim and MacArthur Fellowships, and has served as the President of the American Philosophical Association as well as currently serving as a Fellow of both the British Academy and the American Academy of Arts and Sciences.