This book solves one of the great puzzles of history: Why did the West become the most powerful civilization in the world? Bruce Bueno de Mesquita presents a revolutionary new theory of Western exceptionalism: that a single event in the 12th century changed the course of world history. By creating a compromise between churches and nation-states, the 1122 Concordat of Worms incentivized economic growth, facilitated secularization, and improved the lot of the citizenry, all of which set European countries on a course for prosperity.