This is the first comprehensive study of how different ethical traditions deal with the central moral problems of international affairs. Using the organising 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. Written by leading specialists in the US and UK, this book treats the subject of international ethics in an encyclopaedic way. It allows readers to identify internal tensions within, as well as points of agreement and disagreement between, a wide variety of traditions.