Why is the world racked by barbarity and violence? In this provocative little book, the Nobel laureate economist argues that the causes are as much distorted identities as nasty intentions. When people acquire a strong and exclusive sense of belonging to a single group, Sen notes, the conditions ripen for conflict and violence; when shrunken and shorn of its layered complexity, identity can kill -- Hutus massacre Tutsis, for example, when they no longer see themselves also as Rwandan, African, laborers, and human beings. Sen suggests that sectarian hatreds around the world -- in places such as Kosovo, Bosnia, Rwanda, Timor, Israel, Palestine, and Sudan -- are ignited or exacerbated by illusions of unique and choiceless identities, leading Sen to take issue with Samuel Huntington's "clash of civilizations" thesis. When civilizations conflict it is because of a failure -- often a cultivated failure -- to appreciate the true diversity of identities that infuse them. Sen eloquently describes the dangers of this flattening of human identity. He is less clear, however, about how to nurture a global environment where the richness and multiplicity of identities can thrive.