New polling from Scotland shows a marked increase in support for independence—meaning next week’s referendum is likely to be extraordinarily close. Now that a Scottish decision to separate from the UK seems distinctly possible, the question of currency has gained new urgency. Will Scotland establish its own currency, join the euro, or remain on the English pound? The pro-independence camp, as Matt Yglesias notes, has promised to keep Scotland on England’s pound sterling—but as Yglesias writes, while “a rump United Kingdom couldn’t stop Scotland from using sterling,” it would nonetheless “have no particular reason to make institutional changes that would make a sterling union more workable for the Scots.” Paul Krugman concurs, adding this warning: “everything that has happened in Europe since 2009 or so has demonstrated that sharing a currency without sharing a government is very dangerous.”

The apparent left-of-center consensus on this question is intriguing, since Scottish independence has been sold (dubiously, in my view) as a left-wing cause. And the debate over currency—just like the broader debate over independence—raises an interesting question about just who should have the right to make these decisions. Left-wing sympathizers with the Scottish cause might have bristled at this sentiment, voiced yesterday by Andrew Sullivan:

And since “Britain” is at stake, why should one small part of it be the only part that has a say? What do the English think about Scottish independence? Or the Welsh? Or the Northern Irish? Why shouldn’t they be a part of the deliberation? I guess it says a huge thing about British democracy, decency and fairness that Scotland is being allowed this no-fault divorce option (one only has to look at Ukraine to see the alternative)—but it also says a lot about the way Scotland often wants to eat its cake and have it too.

Supporters of the Scottish cause might regard this way of framing the question as quite unfair—after all, giving the rest of the UK power over Scotland’s independence seems to leave a decision over Scotland’s liberation up to its oppressors. But I have heard this exact point echoed by British leftists who regard Scottish complaints as somewhat overblown—the Ukrainian counterexample is instructive—and who cannot think of a justified reason for leaving the rest of the UK out of the decision, especially since it will have ramifications beyond Scotland.

One of these, which the English left has particular reason to worry about, is the guaranteed body blow that Labour will suffer if Scotland departs. As Dave Weigel notes, there is a general election in just seven months, and Labour is leading in the polls. It could win, Weigel writes, “take power…and then lose power in 2016, when Scotland goes independent and 40-odd Labour members of Parliament suddenly hold foreign passports.” Nor is it inconceivable that, should an independent Scotland remain on the English pound sterling (as independence movement leaders have promised), and should its economy crash (a definite possibility), economic shockwaves could ripple throughout the rest of the UK, even after a formal separation. Although I can imagine a few arguments, it’s not immediately obvious, given the rocky economic foundations of Scottish independence, why the rest of the UK should be denied a say in this decision. And if economic collapse does occur in the newly independent Northern neighbor, there might well be calls for the UK to step in anyway and provide relief—that is, if the ties of history and identity are as strong as the anti-independence “Better Together” campaign says they are.

Of course, after September 18th these questions might vanish, at least for a while. The referendum could fail (barely), and the debate would be postponed until the next inevitable vote. But if it passes, the entire UK—not just Scotland—will have to face these very difficult questions in short order. Most of those affected, although they had no say in the decision, will nonetheless find themselves scrambling to deal with the consequences. Even if Scotland votes to break with the UK, a range of UK actors (from Labour politicians to the Bank of England) will still find themselves forced to address a raft of knotty Scottish dilemmas. Separation, in other words, might not be so easy to achieve.