Will the eurozone survive its crisis? That was the question I raised three weeks ago. My answer was: yes. My argument was that economic self-interest and political will would combine to preserve the common currency, in spite of the difficulties.

Yet that raises a further question: have leaders now done enough to put the eurozone on a sound footing? The answer is: no. Progress has indeed been made. But more will be needed, both intellectually and institutionally. Evidently, I am assuming that further shocks will compel further reforms. That is my judgment. It cannot be a certainty.

The euro is a unique project. For sovereign states to share a currency demands solidarity and discipline. The more diverse are the component economies and the more divergent is their performance, the greater is the need for solidarity and the smaller is its likely supply. So it has proved. I was one of the many who believed that a stronger political union and greater economic flexibility would be needed if the eurozone was to survive in the long run. Only in a crisis would it become clear whether the conditions for survival would be met. This crisis provides the test.