THE IMPOSING TORRE del Mangia is a 289-foot tower rising over Siena’s city hall. Below, the Piazza del Campo serves as the Tuscan town’s market square, civic meeting place, and entertainment venue. Together they form the metaphor in the title of The Square and the Tower, the British historian Niall Ferguson’s new book about networks, hierarchies, and how they have interacted throughout history.
How hierarchies operate is not a conceptual mystery. The emperors of Rome, the caliphs of Islam, the autocrats of the Kremlin, the armies of Napoleon and Eisenhower, the corporate managers of General Motors, the bosses of the Teamsters Union: In each case we see a Mr. Big at the top of the tower directing lieutenants, satraps, prefects, and legates, all the way down to the grunts at…
