The conductor Carlos Kleiber emigrated as a child from Nazi Germany to South America, spending his teenage years there. To judge from Youtube videos of rehearsals, he spoke both English and German fluently but with an accent. Perhaps his Spanish was word-perfect, but what does that mean? Alan Turing proposed the test named after him, that if someone talking to a computer through a link couldn’t tell it from a human being, then it could be considered sentient. Judging a person’s linguistic competence by their ability to “pass” is similarly unreflective about what constitutes the achievement in question, though in either case it’s a tough challenge. I recently met an Englishman — unmistakeably, uncontestably so by that criterion — born and bred in Paris, to English parents. Having lived in Brazil for eight years or so, my own English has had little recent fresh input, and there were a couple of occasions during the conversation when we both stumbled. The accent is so telling because it is part of one’s social and cultural identity, within a language as well as between languages, and it’s surely for that reason it is unusual for adult learners of a new language ever to “pass” for native. But it is a marker of native competence, not its substance. That is made up of tranches of lived experience in the language in question such as having passed through the education system speaking it, as well as reading and writing more generally. The monoculture of the nation-state favours the concentration of identity and experience within a single language for each individual — the melting-pot washes away difference in three generations — but it was not always so and need not always be today. Woodrow Wilson’s criterion of linguistic self-determination to reshape the map of Europe a century ago instituted rather than reflected the sweeping away of the cosmpolitanism of two defunct empires, Ottoman and Austro-Hungarian, with messy and ugly consequences up to the present.