The idea that what goes around comes around applies not only to individuals but to nations and whole civilizations. It was just a few centuries ago -- not long, as history is measured -- that China had the highest standard of living in the world and the Dutch were the world's largest exporters, while North Africans were enslaving a million Europeans. Nowhere have whole peoples seen their situation reversed more visibly or more painfully than the peoples of the Islamic world. In medieval times, Europe lagged far behind the Islamic world in science, mathematics, scholarship, and military power. Even such...