Multiculturalism has reached its moment of peril. Multiculturalism, as public policy, as a way of life, could disappear altogether, relegated to a figment of history, a relic.

The counter-reaction to global trade, to globalization generally, has been a deep retreat behind borders. The recent election in Hungary, in which Viktor Orban ran and won on a loathing for immigrants and “foreign meddling,” is only the latest example of a militant and triumphant xenophobia seen everywhere. The consequences of the Brexit vote are starting to harden; non-English Londoners, once the definitive cosmopolitans, are stumbling back dazed to home countries they long since stopped considering home. The United States, the country with e pluribus unum on the money, separates immigrant children from their parents in detention camps on its borders. The most liberal societies are taking on illiberal attitudes: Denmark has announced special regulations and requirements for “ghetto children.”

By no means is the xenophobia limited to Western countries or fully developed economies. Hindutva dominates Indian politics. The so-called Communist government of China has no relationship whatsoever with the international proletariat. Nationalism is its legitimating ideology, and no other. In the face of an opening world, the most egregious stupidity of humanity — pride in blood — has reasserted itself with a vengeance.

It’s not just recent elections, either. It’s not just politics, even. Culture, too, is closing itself off, partitioned along ethnic lines, and patrolled by stewards of rage and loathing. In the West, the idea of cultural exchange has become fraught by its reduction to categories of cultural appropriation. Similar processes of separation and purification are evident everywhere else, too. Bollywood — what has been called the greatest pluralistic culture industry in history — banned Pakistani actors two years ago. Pakistan responded by banning Indian films. A recent Bollywood film, Padmaavat, caused massive riots before it was even released because it was rumoured, just rumoured, to contain a romantic relationship between the Hindu Queen Padmavati and the invading Muslim King Alauddin Khilji. The film turned out to dehumanize Muslims fully enough — indulging to the maximum the stereotype of the dead-eyed rapist Islamic invader — but even the possibility of a cross-cultural connection provoked the burning of Muslim school buses. Real violence follows closely behind the imaginary.

In both politics and culture, the lines between in-groups and out-groups are thickening, sometimes subtly, sometimes sharply. Ethnic nationalism relies on a profound sense of victimhood, even among groups that are self-evidently established and prosperous. The English are the victims of Europe, so they need Brexit. The Americans are the victims of the world economy, so they need to rid themselves of immigrants. The Bharatiya Janata Party in India operates under the all-consuming premise that Hindus are the victims of the Muslims. Paranoia is the new norm. Context vanishes. Each defines themselves by their enemies.

Even a few years ago, those of us who grew up in open societies more or less assumed that the world was tending inexorably towards more openness. The argument went something like this, although it was not so much an argument as an impression, an assumption: Trade throws us together in cities. Cities are the seat of power and influence. When they live together people tend to encounter each other as people. They eat each other’s food. Their children sleep with each other and end up having children together. Everyone prospers. Democracy and freedom of trade underlie that prosperity, and ensure progress towards fundamental respect for human dignity. The faith in globalized tolerance was the faith of Francis Fukuyama’s famous essay “The End of History?,” which seems more ludicrous by the day. That essay is now a relic of the assumption of the power of democracy and tolerance that the global elite once widely shared. Many literally believed there was no other way to live.

That confidence was obviously misplaced, and it blinded us to our responsibility to defend multiculturalism. The atavism of blood haunts us in ways we imagined we had already exorcised through the various mass slaughters of the twentieth century. The widening middle classes of the developing world and the shrinking middle class of the developed world increasingly take their values from half-inherited, half-imagined hatreds. Meanwhile the world swells with stateless peoples, a vast and expanding pool of mostly ignored suffering. It is now, at this moment of darkness, at this moment of deep unpopularity, that we most need to understand why multiculturalism is so necessary, so glorious. Openness towards others is neither easy nor inevitable, as we believed a decade ago. Rather the opposite. Multiculturalism is difficult and unlikely and fragile. That’s why we have to fight for it.