Lebow argues that foreign policy guided by ethical principles tends to be more effective than the alternative. Approaches to international relations that rest on sharp distinctions between the 'is' and 'ought' foster an inaccurate picture of the world and encourage unethical policies justified by reference to national interests. Instead, Lebow proposes a tragic theory of world politics sensitive to ethical principles and shared standards of justice but that eschews deontological universalism in favour of moral pluralism. A familiar tension runs through Lebow's account between, on the one hand, a sense that there are generally accepted moral norms against which to judge behaviour and, on the other, a sense that there are radical – perhaps incommensurable – differences between the world's moral systems. Lebow's suggestion that human rights have become part of our 'what is' sits uncomfortably with the persistence of moral systems that reject some basic rights (such as gender equality). But that is the point: there is inescapable normative tension in world politics managed best not by casting ethics out but by aligning foreign policy with shared ethical principles and using policy to shape them. That is where tragedy comes in, as a reminder that even the powerful must listen to other voices, engage with them, making compromises where necessary – things that do not come easy to great powers. But this approach, Lebow demonstrates with reference to datasets and case studies, makes for more ethical and effective foreign policy. Some might wonder whether this relationship between ethics and efficacy is tautological, others might question the datasets that guide Lebow's analysis, but all will find a cogent, compelling, and creative contribution to international political thought.