Ever since the federal republic was founded, Germany has had two over-riding strategic objectives: sound money and European integration. These were the twin imperatives learned from the calamities of the early 20th century. The euro embodies these aims. Now they conflict with each other.

Is the right answer to rescue sinners, thereby strengthening the cohesion of the eurozone, but threatening monetary stability? Or is it to let sinners default, thereby strengthening monetary credibility, but weakening cohesion? Germany could avoid such choices before the single currency: uncompetitive countries simply devalued.

Unfortunately, the domestic German debate assumes, wrongly, that the answer is for every member to become like Germany itself. But Germany can be Germany – an economy with fiscal discipline, feeble domestic demand and a huge export surplus – only because others are not. Its current economic model violates the universalisability principle of Germany's greatest philosopher, Immanuel Kant.