Institutions — not geography, culture, or other factors — explain why some nations succeed and others fail. So says Daron Acemoglu in an ambitious new book drawing evidence from thousands of years of human history and from societies as diverse as those of the Inca Empire, 17th century England, and contemporary Botswana. Inclusive political and economic institutions, influenced by critical junctures in history, produce virtuous cycles that reinforce pluralism in the market and in politics.