When David Lipton, a promising economist, was finishing his graduate work at Harvard in the early 1980s, he faced one of those potentially life-changing choices. He had one job offer from the International Monetary Fund in Washington, the multinational institution that for 70 years has served as a lender of last resort and dispenser of orthodox economic advice to countries that get into financial trouble. There was also an offer of a teaching job from the University of Virginia. Unsure of which path to take, he turned for advice to an intellectually restless and charismatic assistant professor, a Frenchman named...