In a period of rapid internationalization of trade and increased labor mobility, is it relevant for nations to think about their moral obligations to others? Do national boundaries have fundamental moral significance, or do we have moral obligations to foreigners that are equal to our obligations to our compatriots? The latter position is known as cosmopolitanism, and this volume brings together a number of distinguished political philosophers and theorists to explore cosmopolitanism: what it consists in, and the positive case which can be made for it. Their essays provide a comprehensive overview of both the current state of the debate and the alternative visions of cosmopolitanism with which we can move forward, and they will interest a wide range of readers in philosophy, political theory, and law.