The only uncertainties now are the terms of a Greek default, what the wider damage will be, and how to limit it. The fact that politicians have painted default as an unthinkable catastrophe does not help. It will be messy—yet no less messy than the political confusion that has stymied decisions for the past 18 months.

Writing down Greek debt by, say, 60 percent would saddle the European Central Bank with a big bill; create holes in the balance sheets of some big French, German, and Belgian banks; and, to an unknown extent, expose British and American holders of credit default swaps. Not only Greek but Romanian and Bulgarian banks could collapse, while Cyprus’s exposure to Greek debt is 156 percent of its GDP—and Russia holds massive deposits in Cyprus. But as Timothy Geithner has observed, the eurozone is not exactly penniless, and should be able to recapitalize banks that need it. The harder task will be to calm the European bond market, starting by providing Ireland and Portugal, which are in the recovery ward, with sufficient liquidity to ride out the storm. The European Central Bank will also need to buy Spanish and Italian bonds—but on the condition that their pampered politicians take the sort of steps Italy balked at this summer, notably the total abolition of Italy’s pointless and costly layer of provincial government.

The biggest risk is political. Rather than buckle down to restoring confidence, Europe’s politicians are bent on another time-consuming redesign.