Should nations intervene in other countries to prevent human rights abuses or famine? On what principles should immigration be based? Should wealthy states aid poorer states, and if so, how much? Who should pay for global environmental damage? Answers to these moral questions depend to a great degree on who we believe we have an obligation to: Ourselves? Nationals of our country? Residents of our country? Everyone in the world equally? We will examine different traditions of moral thought including skeptics, communitarians, cosmopolitans, and use these traditions as tools to make reasoned judgments about difficult moral problems in world politics.