The spread of capitalism worldwide has made people wealthier than ever before. But capitalism’s future is far from assured. The global financial meltdown of 2008 nearly produced a great depression. Economies in Europe are still teetering. Income inequality, resource depletion, mass migrations from poor to rich countries, religious fundamentalism—these are just a few of the threats to continuing prosperity. How can capitalism be sustained? And who should spearhead the effort?...