Ethics, Diversity, and World Politics argues for the importance of the diversity of human ethical systems in world politics, defending the vitality of a 'pluralist' position in debates about how to ethically assess and respond to political challenges. Rooted in the 'English School' tradition of international relations theory, the book offers the first fundamental reformulation of the 'traditional pluralism' that fails to offer a persuasive defence of the normative desirability of ethical diversity in human affairs, resulting in a pluralist ethic that is statist, conservative, and unable to engage effectively with contemporary world politics. The book develops an alternative account of 'revived pluralism', rooted in a defence of the normative desirability of ethical diversity that draws upon political philosophy, political theory, and sociology, to establish a far more rigorous methodological basis for a pluralist position, whilst also enabling assessment of the limits of defensible diversity.