And there were large communities of cosmopolitan expatriates — “passeurs” between cultures, notably urbanized Jews, as well as German minorities, scattered throughout Central and Eastern Europe. Though prejudice ran deep and they were harshly mistreated in many places, in others they could identify as citizens of a broader European group, not merely the land they inhabited, and aspire to respect and comfort.

Later, at the hands of totalitarians, most of the Jews would be slaughtered, and the Germans — like other groups — deported to their country of origin. Alongside their greater crimes, Hitler and Stalin thus did their parts to erase the idea of cosmopolitanism as the old Europe had understood it.

Which makes the usual starting point of the modern European narrative — the rubble of 1945 — all the more poignant. An overwhelming imperative to rebuild, augmented by the cold war, united Western Europe and pushed West Germany center stage. Europeans prospered in an increasingly common market. But the unifying element was not optimism as much as dread — fear of another war among themselves or of Soviet expansion was what spurred West Europeans to bridge differences if they developed.

After the Berlin Wall fell, Western Europe expanded east and seemed to be serenely approaching the End of History — peace, prosperity, social security, democracy, with a unifying token, the euro, from Helsinki, Finland, to Seville, Spain. For its more than 400 million people, Europe became a theme park, museum, supermarket — the EasyJet continent: efficient, fast, open to all at little cost.

But now Europe asks for sacrifices and solidarity, and it finds itself on the decline. Everywhere, populists and nationalists gain. Managing austerity, fighting debt — this, it turns out, is no way to unite Europe.