What obligations do the world's wealthy people have to ensure that the world's poor achieve a quality of life that is recognisably human? This is the fundamental question of international distributive justice, and surprisingly a question that has been the subject of serious debate only in the past three decades. This book outlines and evaluates the main competing moral perspectives framing these debates, assessing the relative merits of the utilitarian, human rights, and neo-Kantian perspectives before answering the nationalist, patriotic, relativist, and constitutivist challenges to moral universalism. The book defends a form of cosmopolitanism involving a commitment to basic human rights, and provides both a guide to the state of the art in disputes about global justice, and a distinctive defense of the moral case for change in the international system.