I’m a fan of Catalonia but Catalan separatists are separating people. Their slogans say, “Spain steals from us!” or “Catalonia is not Spain”. Rhetoric like this divides people into opposite groups, each with a single identity: us (Catalans) and them (Spaniards). You must be one thing or the other. The government in Madrid unintentionally sharpens this divide by locking up separatist leaders.

Someone else who thinks in terms of single identity is Donald Trump. As he tells it, you’re American or Muslim; you’re a real American or a liberal elitist. There’s an uncomplicated joy to single identity: find your essence, then taunt an enemy who doesn’t share it. And along with your identity comes a free set of opinions that you never need to test against reality.

But thinking in single-identity terms breeds conflict. JH Elliott, the British historian and expert on Spanish history, describes Catalonia as “a very unhappy society over the last year or two”, in which “families have not been talking to each other”. Some disappointed Catalan separatists could easily morph into a terrorist movement like the Basque ETA or the IRA.