Genuine cosmopolitanism is a rare thing. It requires comfort with real difference, with forms of life that are truly exotic relative to one’s own. It takes its cue from a Roman playwright’s line that “nothing human is alien to me,” and goes outward ready to be transformed by what it finds. The people who consider themselves “cosmopolitan” in today’s West, by contrast, are part of a meritocratic order that transforms difference into similarity, by plucking the best and brightest from everywhere and homogenizing them into the peculiar species that we call “global citizens.” This species is racially diverse (within limits) and eager to assimilate the fun-seeming bits of foreign cultures — food, a touch of exotic spirituality. But no less than Brexit-voting Cornish villagers, our global citizens think and act as members of a tribe.