The dynamics are different in each case. Though the nationalists lost Scotland’s 2014 independence referendum, a significant minority of 45 percent of Scots voted to leave the U.K.; meanwhile, Scots favored EU membership by a large margin in the Brexit referendum, with 62 percent voting in favor of staying. Would pro-EU sentiment be enough to push Scottish public opinion that last little bit in favor of independence? Would Scots be inclined to leap out of one union, the United Kingdom, for the sake of a different one, the EU? Polls taken prior to the referendum have suggested it’s not that simple—earlier this month, independence was not that much more appealing to Scots facing the prospect of Brexit than it was to Scots in 2014—and Scottish politicians have urged caution. Kezia Dugdale, the leader of the Scottish Labour Party, argued against a new referendum: “On the question of independence, many of the fundamental questions that were unresolved and unanswered in 2014, remain so,” she said. These include basic matters like what currency an independent Scotland would use (Scottish pounds? British pounds? Euros?). “What we don't need today is more turmoil, more upheaval and more economic chaos.”

On the other side of the Irish Sea, Northern Ireland will have the only land border between the United Kingdom and the European Union; it shares an island with the Republic of Ireland, an EU country, to the south. The implications of Brexit for this border, which has heretofore been open under EU freedom-of-movement rules, are not yet clear. But as Naomi O’Leary reported for The Atlantic earlier in the week, a stronger division of the Irish island is a potentially explosive issue—it’s one people in Northern Ireland fought over throughout the Troubles, the period of violence beginning in the late 1960s in which some 3,500 people were killed before the Good Friday Agreement, backed by the United States and Britain, stopped most of the fighting in 1998. As O’Leary noted: “The EU has pumped funding into projects to promote cohesion, and the region’s peace agreements are underpinned by EU law.”

But perhaps a more fundamental issue is that the open border between Ireland and Northern Ireland helped obviate an underlying cause of the conflict. Catholic nationalists had fought to unite Ireland’s north and south; Protestant unionists had fought to keep the north in the United Kingdom. Under EU arrangements, there was something for everybody; Ireland was “united” in certain ways, even while the U.K. exercised sovereignty over the north. But following the referendum—in which Northern Ireland voted to remain by a margin of 56 to 44 percent—the chairman of Sinn Fein declared that the British government had “forfeited any mandate to represent the interests of the people here in the north of Ireland in circumstances where the North is dragged out of Europe as a result of a vote to leave.” (The leader on the unionist side pronounced the outcome a “good result.”)