Scholars of international relations rarely look at culture as a force in world politics. Theorists tend to focus on power and interests, not values. In this ambitious book, Reus-Smit seeks to change that. His first discovery is that scholars acknowledge the role of cultural interactions more than one might think. Samuel Huntington famously depicted a “clash of civilizations,” and realists sometimes make arguments about the effects of nationalism. Liberal and rationalist theories of politics often note how better cultural understanding can make cooperation easier. But Reus-Smit argues that scholars conceive of culture as fixed rather than fluid. He also points out that all the great international orders in history—the Roman Empire, the Qing dynasty, the Ottoman Empire, and early modern Europe—evolved in heterogeneous cultural contexts. Grappling with such diversity, Reus-Smit argues, is one of the great tasks of order building.