AP Photo

This summer, many government officials and private investors finally seemed to realize that the crisis in the euro zone was not some passing aberration, but rather a result of deep-­seated political, economic, and financial problems that will take many years to resolve. The on-again, off-again euro turmoil has already proved immensely damaging to nearly all Europeans, and its negative impact is now being felt around the world. Most likely there is worse to come—and soon. But the economic disasters of our time—which involve big banks in rich countries, call into question the viability of government debt, and seriously threaten the reach of even the most self-confident nations—will not end with the euro debacle. The euro zone is well down the path to severe crisis,...