Scanlon's What We Owe to Each Other (1998) develops and defends a distinctive approach to interpersonal morality, known as contractualism. Scanlon’s idea is that interpersonal morality—giving others their due—involves being able to justify your conduct to others. Doing right by other people means treating them in ways they cannot “reasonably reject.” More recent work includes a subtle account of the role and function of moral blame in Moral Dimensions (2008) and, in 2014’s Being Realistic About Reasons, a defense of a kind of moral realism, the claim that moral truths exist independently of humans’ beliefs and attitudes.

While Scanlon has been a system-builder in moral philosophy, his work in political philosophy, by contrast, focuses on particular values. His 2003 book The Difficulty of Tolerance includes an account of freedom of expression as well as insightful essays on toleration, human rights, and punishment, among other topics. Now Scanlon is at work on a book whose subject has concerned him for a long time, but which has in just the past five or so years emerged as a central axis of political debate: inequality.