IN HIS novel “Exit West”, Mohsin Hamid describes a world very like our own, but which is suddenly changed by the appearance of mysterious doors. A dark-skinned man falls out of an Australian woman’s wardrobe in Sydney. Filipino women emerge from the back door of a bar into the alleyways of Tokyo. As the incidents multiply and scores of people from poor countries walk through the doors into richer ones, rich-world inhabitants respond with violent resistance. Governments crack down hard on the new arrivals. But it is not long before they are overwhelmed by their sheer number and abandon efforts to repel them. The world settles into an uneasy new equilibrium. Shantytowns emerge on the slopes of San Francisco Bay. Conflicts in war-torn places burn out for want of civilians to kill and exploit.
Mr Hamid’s story comes close to what many advocates of open borders believe the world would look like if people were free to move wherever they wanted: fairer, freer, with more opportunities for a larger number of people. But it also nods to the fears many people have about unfettered migration: uncertainty, disorder, violence. Would such a world be a dream or a nightmare? The answer depends on whom you ask.
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Few things have caused citizens in Western liberal democracies more angst in recent years than borders and migration. In the United States, voters chose a president in 2016 who promised to build a wall to stem the flow of migrants from Mexico and elsewhere in Latin America, and who has since sought to ban people from several Muslim-majority countries from travelling to America. In many European countries, right-wing parties have risen to prominence on an anti-immigration platform. Concerns about immigration played a major role in the British vote to leave the European Union in the summer of 2016. When Angela Merkel, Germany’s chancellor, opened her country to hundreds of thousands of refugees from the Syrian war in the summer of 2015, she was applauded for her humanitarian impulse. But two years later, German voters punished her party at the polls for what many now argue was a rash and irresponsible decision. A big share of the vote went to…