In this inspiring meditation on global ethics, the eminent political philosopher Appiah poses old questions made urgent by globalization: What does it mean to be a citizen of the world? What do we owe strangers by virtue of our shared humanity? Appiah's answers emerge in an engrossing synthesis of autobiography, history, literature, and philosophy. The author's own personal story -- son of an African father and English mother, raised in Ghana, educated in the United Kingdom -- nicely fits the border-crossing themes of the book, the central goal of which is to rethink the moral principles of cosmopolitanism, the centuries-old tradition that rejects tribalism and nationalism in favor of a wider embrace of human community. Two strands of cosmopolitan thinking -- one that stresses global obligations, one that celebrates local differences -- help frame the tension between preserving local values and communities and seeking universal standards. Through anecdote and principled argumentation, Appiah tries to find an ethical terrain that allows for the flourishing of both, a cosmopolitanism in which individuals can give expression to a multiplicity of identities and loyalties while building an enlightened global community through dialogue and discovery.