Listening in on the altercation between Rome and Berlin about the inviolability or otherwise of the eurozone’s fiscal rules, it is tempting to conclude that an irresistible force is hurtling towards an immovable object. Tempting, but misleading.

The argument between Italy’s Matteo Renzi and Germany’s Angela Merkel is real enough. It asks a question at the heart of the future of Europe’s single currency. Can an arrangement that will always fall well short of a textbook monetary union be at once economically robust and politically sustainable? Germany – joined by other northern states – likes to focus on the first of these conditions; Italy and other more indebted economies on the second. The two, of course, should be seen as self-reinforcing. The challenge is to find the equilibrium.

On some things Berlin and Rome agree. The other day I heard a senior member of Ms Merkel’s government remark that the eurozone’s most precious asset is credibility. A week earlier one of Mr Renzi’s colleagues offered precisely the same judgment at a private gathering in Rome hosted by Aspen Institute Italia.