Do any needs defensibly make claims on anyone? If so, which needs and whose needs can defensibly do this? What are the grounds for our responsibilities to meet others' needs, when we have such responsibilities? The distinguished contributors to this volume consider these questions as they evaluate the moral force of needs. They approach questions of obligation and moral importance from a variety of different theoretical perspectives, including contractarian, Kantian, Aristotelian, rights-based, egalitarian, liberal, and libertarian perspectives.