The news of the Brexit vote—for all that it had been obviously plausible for years, highly possible for months, and even on the very eve was known to be at best a hairbreadth business—still shocked Europe, and perhaps the world, as no political event has since the fall of the Berlin Wall. The momentum toward pluralism, openness, the eradication of borders, and transnational consciousness, however hesitating or troubled its evolution, had been the civilizational momentum of our era. Suddenly, it seemed to stop. It was as if the moon had been called off, the tides pulled back in mid-flow. I happened to be in Iceland, at the very top of Europe, when it happened, which was, by a variety of improbabilities, a good place to witness the tide of time suddenly reversed. Iceland is, among other things, among the most “globalized” of small nations, where Wi-Fi penetrates to places that, half a century ago, were unchanged since the saga days, and where Americans and Australians and Icelanders flock together to make eclectic pop music for the planet. (Iceland, though only what might be called an associate of the European Union—it is a member of the European Economic Area—still accepts the free movement of its peoples.) It is also in the midst of a fairy-tale ascent in the competition that marks the sublimation of European national rivalry into sports—a fairy tale that became even more fabulous when the tiny country defeated (O.K., Brexited) England right out of the competition. Football, Bridget Jones says somewhere, is what men have instead of emotions, and the Euro competition was what Europe now was thought to have instead of wars. Iceland had done so well in the competition, taking place in France, that a huge chunk of the tiny population had gone off to Paris to support the team—a sure sign of open movement, general rebounding prosperity, and positive exchange. (One reason that the team has been so improbably good is that its best players have gained experience in the English Premiere League, which was effectively closed off from Europe for decades, until 1995, when the European Court of Justice, in a case brought by a Belgian player named Jean-Marc Bosman, opened it up, to the vast advantage of English football, an advantage that may now very well be abruptly shut down.) As the next day dawned in Britain, and the truth of why what had happened had happened began to penetrate, it was clear that the progressive desire to pretend that the vote was primarily an assertion of economic insecurity or a statement against neoliberalism was, as so often in the past, at best very partial, at worst sentimental and self-deluding. What was really at stake was a closed vision of the future against a cosmopolitan one. The divide was much less the prosperous versus the poor than it was city versus small towns, the well-educated versus those without advanced degrees, and, most of all, the young versus the old. Economic insecurity was, obviously, one of the things that drove the vote, but nostalgic nationalism drove it more, and what was really striking was that the struggling young took it for granted that the way toward a better future lay in ever-more European and planetary consciousness, not in closing it down. The vote was intolerably cruel in particular to the twentysomethings of Britain, many of whom did not hesitate to protest. They had gone to sleep on Thursday evening with all the world, or at least with all of Europe, before them, as citizens with possible futures in twenty-eight nations; they woke on Friday morning to be told that their future would contract to one nation, and that one possibly shrinking before their eyes, right to the Scottish border. Above all, the divide was about natives and newcomers—or, rather, between old newcomers and new newcomers, or between natives and their phantom image of what the newcomers were like. It was a vote on immigration, or its spectre. That immigration might be a net economic benefit, not a “drain”; that the immigrant populations that seemed hardest to assimilate had arrived, in large part, due to a kind of postcolonial payback that had little or nothing to do with the E.U.; that, indeed, the E.U. had little to do with many of the social strains that immigration was imagined to impose on social services—these were invisible truths, overwhelmed by tabloid telegraphy. The larger economic truth that wealth is productivity, and that it is hard to imagine the free movement of goods without a free movement of peoples (a truth discovered, ironically, by English economists in the face of French Enlightenment resistance), was lost, too. Some of the fears, to be sure, were not fictive. The role of terrorism, and particularly of the terrorist attacks in Paris and Brussels last year, in radicalizing otherwise tolerant English people, can’t be overestimated. The idea that host countries had allowed in their midst immigrant groups who, far from assimilating, had used the resources and generosity of these countries to seed violent attacks on their citizens seemed intolerable. This conclusion might have been overplayed, but it wasn’t imaginary. The broader truth of the recent waves of immigration, the truth of a million small assimilations and adjustments, was easily lost in the tabloid terrors. (Some of my own family happened to be spending the evening of the Brexit vote in Paris, with French Muslim friends who had arrived in France only in the nineties. They were celebrating the advancement of their son to an élite French public school; he had also been named one of the best athletes in his arrondissement.) Thinking of Europe now, I often come back to a scene in a Reykjavik pub, during the European soccer-championship competition, when Iceland was playing Austria. Twenty-five television screens were showing the Iceland-Austria game, with exactly one screen, in a small corner, devoted to the simultaneous Portugal-Hungary game. Two Portuguese workers came in, stood in the doorway, and watched their game, against the current of the crowd. They looked like figures in a Sempé drawing, their gaze gallantly running in the opposite direction of everyone else’s. But the toleration they received, along with the one screen courteously left on for their benefit, even in the midst of national fever, also seemed to summon up what is right about the European project: just enough good manners to bring very different peoples together in a single space and make polite their passions. (A Brit, of the unduly cheery, blokeish kind, meanwhile, came in and ordered a mojito, puzzling the Icelandic bartender, who dutifully followed the recipe. Soon much of the bar was drinking mojitos. Brexit really will have its costs.) The question always rises: What has the E.U. ever achieved? Only the longest period of peace and prosperity in modern European history, a peace and prosperity that might have been due to absurd elements of overplanning and bureaucratic centralization but that also helped create those small rituals of international courtesy that that Icelandic pub witnessed. Anyone who thinks that absurd elements of overplanning and bureaucratic constraint are the worst evils Europe has recently experienced should try the Battle of the Somme. Or Verdun. Or any of the other annihilating battles whose centenary we celebrate, or mourn, this year. It is a sign of the success of the European Union that such scenes seem now to belong to the realm of the purely imaginary. They don’t. There’s no reason they have to. At this moment, two irascible émigrés from the past century of European tragedies might come to mind. John Lukacs, the Hungarian-American historian, has spent a lifetime arguing that nationalism—not socialism, or even liberalism—is the core ideology of modernity, and that the lesson of history is that nationalism will assert itself, like an unquenchable microbe, anytime it has the least opportunity. (He also draws the distinction between patriotism—the love of place and tradition and a desire to see its particularities thrive—and true nationalism, which is a vengeful, irrational certainty that the alien outside or even within a country’s borders is responsible for some humiliation to the true nation.) This pessimistic strain was matched by that of Karl Popper, the Austrian-Anglo philosopher, who saw that what he named the “open society,” though essential to the transmission of humane values and the growth of knowledge, can impose great strains on its citizens—strains of lost identity, certainty, tribal wholeness. The reaction to this strain is inevitable, and sure. What keeps an open society from being overturned is only the balm of ever-increased prosperity; when prosperity ends or is endangered, all the bad demons come out of the forest. In this much broader sense, it may be prosperity that makes pluralism possible. Economics alone don’t drive the ideology of nationalism, but without prosperity it has more room to bloom. Meanwhile, nationalism won’t just go away, and open, liberal societies are far more fragile than their success can make them seem—and these two sad truths seem to need perpetual restating, or the lights really will go out across Europe.