This is the first comprehensive study of how different ethical traditions deal with the central moral problems of international affairs. Using the organizing concept of a tradition, it shows that ethics offers many different languages for moral debate rather than a set of unified doctrines. Each chapter describes the central concepts, premises, vocabulary, and history of a particular tradition and explains how that tradition has dealt with a set of recurring ethical issues in international relations. Such issues include national self-determination, the use of force in armed intervention or nuclear deterrence, and global distributive justice.