A new "constructivist" approach to international politics has been gaining ground in recent years, emphasizing the role of shared ideas and norms in shaping state behavior. A leading figure in this movement, Wendt takes aim at realists and liberals who stress materialist or individualist causes of state action. For Wendt, the beliefs that states hold about each other determine international politics -- and these ideas are constructed largely through social relationships rather than material realities. Power and interests do matter in world politics, but shared knowledge determines their significance in deciding whether states opt for balancing, cooperation, or war. The book first takes a winding tour of social theory to establish constructivism's underpinning before exploring alternative "cultures" of international relations -- namely Hobbesian, Lockean, and Kantian. In the end, the picture of world politics that emerges is not that new, resembling the English School's "society of states" image. The more important contribution is the lucid rendering of the debate between realists, liberals, and idealists. Wendt shows how great the gulf is between these views -- but also develops a language that will allow them to talk to one another.