Could Scotland perhaps join the euro? Now it is the president of the European Commission who says "no" - that would require the agreement of all member states and Spain, sensitive to separatism in Catalonia, is unlikely to agree.
The "yes" camp sees it differently. They think that when push comes to shove, a Britain anxious to retain critical weight will make concessions to keep an independent Scotland close. Perhaps yes: perhaps no.
What is clear is that any separation would involve a bartering session with each side pursuing its crucial interests. Will England be able to use the nuclear submarine base at Faslane? Who gets the revenues from North Sea oil? It would all be up for grabs and the grabbing has to be done after the Scots have made their decision.
Whether the notoriously canny Scots will prove willing to risk their futures in this monumental game of poker remains to be seen but one decision seems likely to rebound on the separatists. The Scottish assembly has insisted on setting the voting age to 16, presumably on the basis that teenagers are more likely than their elders to be influenced by the romantic notion of an independent Scotland rocking to the skirl of the pipes.
Is that why the poll is set for the 700th anniversary of Robert the Bruce's victory over the English at Bannockburn? Will there be compulsory viewing of Braveheart in all schools the day before the referendum? Will the pupils be force fed haggis before they are sent out, as ballot fodder, to do their duty as patriots? No doubt they will - and whisky, too - but how will they vote when they get to the polling booth?
Sixteen-year-olds don't care for being patronised or treated as fools.
If it is their vote which sinks independence, the separatists will have richly deserved their comeuppance.
Whatever the outcome of all this, it should have one useful side effect. The campaigning by both sides must focus on which decisions would be the province of an independent Scotland and which, if any, would be pooled with England.
What powers do you have to retain before you are a nation state. Defence? Economic? Foreign policy? Environmental? Many parts of the world need the answer to that.
In the case of environment, there is surely an incontrovertible argument that policy should be passed up to supra-national authority. Perhaps the time is coming when we will say the same of some of the others as well.
Before retiring, John Watson was a partner in an international law firm. He now writes from Islington, London.