That Europe, and especially the eurozone, has not been doing well since the 2008 crisis is beyond dispute. The single currency was supposed to bring prosperity and enhance European solidarity. It has done just the opposite, with depressions in some countries even greater than the Great Depression. To answer the question about what is to be done, one has to answer another: what went wrong. Some claim that policymakers made a set of mistakes — excessive austerity and poorly designed structural reforms. In other words, there is nothing wrong with the euro that could not be fixed by putting someone else in charge.

I disagree. There are more fundamental problems with the structure of the eurozone, the rules and institutions that guide and constitute it. These may well be insurmountable, raising the prospect that the time has come for a more comprehensive rethinking of the single currency, even to the point of unwinding it.

Put simply, the euro was flawed at birth. It was almost inevitable that taking away two key adjustment mechanisms, the interest and exchange rates, without putting anything else in their place, would make macro adjustment difficult. Add to that a central bank mandated to focus on inflation and with countries still further constrained by limits on their fiscal deficits, the result would be excessively high unemployment and gross domestic product consistently below potential output. With countries borrowing in a currency not under their remit, and with no easy mechanism for controlling trade deficits, crises too were predictable.