Finance is an industry moulded by disaster. It took a civil war to bring America’s banks under federal supervision, a banking panic to create the Federal Reserve and a Great Depression for the government to insure deposits. Yet the reformist urge that burns hot in the moment of catastrophe has a tendency to fade. Lessons are forgotten, innovations happen and regulations become regarded as a nuisance. New risks emerge—as do new titans, who defend their successor system vigorously and convincingly. The conclusion of one crisis begins the countdown to the next.