What role should the idea of evil have in contemporary moral and social thought? The concept of 'evil' has long been a key idea in moral discourse. Now, the contributors to this volume make a start on the important task of systematically exploring evil in the context of political theory.Intuitively, we know what evil means. Yet once we begin to think about its meaning we quickly uncover competing definitions. In recent years, political theorists have generally set the concept aside as outdated or inappropriate. Yet the idea that some things are wrong beyond toleration still has significant currency. If 'evil' can capture that significance, it merits a closer look.