As a dissenter from the determinism that fills many U.S. policymakers and academics with a faith that the arc of history bends in the directions they prefer, Kaplan believes that history, culture, and geography set limits—often grim ones—on what human societies can accomplish. The United States is a great power, he argues in this short but ambitious book, not just because Americans have a successful constitution but also because the United States occupies some of the richest temperate land in the world. The country comprises an immense mass of fertile land watered by the greatest network of navigable rivers in the world—rivers whose flows unite the vast expanse between the Rockies and the Appalachians into an economic (and therefore political) unit. But the size and variety of the country have often made it difficult for Americans to unify around communal visions of national identity and the proper U.S. role in the world. Kaplan notes that the taming and development of the arid American West required new forms of political organization and a more powerful role for government. That experience, he suggests, might provide the inspiration for innovative social policies that could promote social cohesion in the years to come.