One of the most commonly-repeated nostrums of the issue of whether / when there should be a referendum on Scottish independence is that the issue of whether Scotland should leave the Union is a matter for the Scots. But that's wrong, both in principle and in practice.
At one level, it's the kind of thing I might say myself. When I've said that, I meant to contrast the situation for Scotland with that for Wales. Scotland is a country within the Union. There was a union of Crowns, of which the Scottish crown was one, and a fusion of sovereigns. Scotland is a country within the United Kingdom. Wales is not a country at all under the British constitution. It is a region of England-and-Wales. There was no Act of Union of Wales. Wales was simply absorbed under the English crown as part of a process of absorption of Welsh-speaking regions that included Cumbria (probably in the 1050s), Cornwall (in the 1060s) and Wales (in the 1270s). Wales is no more a country than is Cornwall or Strathclyde. It's no more a "matter for the Welsh" whether Wales leaves the union than it is a matter for the Cornish or the East Anglians whether their regions depart, likewise. Those that happen to dwell on a piece of land at a moment of time do not become sovereign over it.
Scotland, on the other hand, is clearly a country. If it wants to leave the Union, that's up to the Scots to decide. But that does not mean it is a matter purely for the Scots, and it a great error to believe that it is. As the Greeks may shortly learn, in order to stay in a union with others, the others must want to stay in union with you.
The key threat to the Union is not that Scots will choose to leave it. It's that the English-and-Welsh will choose to leave the Scots. The Scots rarely offer any sense that their politicians comprehend this point. A recent example was offered by the absurd and arrogant presumption of the Scottish Nationalists that, after "independence" (a false notion, as I shall explain in a moment) Scotland would continue to be part of the Sterling area. As George Osborne quite properly pointed out, there is no guarantee of that at all. There is nothing the rest of the United Kingdom would be likely to want to do to prevent the Scots from using sterling, much as Montenegro uses the euro or Ecuador uses the dollar, but Montenegro is not a euro member. It has no voting presence on the ECB; its banks cannot access ECB last resort lending. Its use of the euro is purely one of piggy-backing.
If the Scots want a Sterling-ised economy, who will stop them? But they are most unlikely to contine as proper members of a Sterling area, because the rest of the Sterling area will not want them as members. A key lesson of the Eurozone crisis is that it is tricky to make currency unions work without full political and fiscal union. But the Scots would be proposing to withdraw from political and fiscal union with the rest of the Sterling area. Recent events suggest that the rest of that area would be unwise to accept its continued membership under these changed terms.
There is another important implication here, for the Scottish Nationalist policy used to be that Scotland should join the euro. If it did leave the Sterling area, euro membership would be its next most likely alternative. It seems unlikely, for example that the Scots would seek to establish their own new currency – especially since European economies establishing their own new currencies over the next few years are likely to have a reputation for devaluation, inflation, and social disorder. If the Sterling area won't have the Scots – and it may well not – Scotland would probably be joining the euro (though nearly 80 per cent of Scots oppose doing so).
But by then euro membership will have very significant implications. For the euro to survive will involve considerable acceleration in fiscal and political integration within the Eurozone. There is likely to be a series of new Eurozone treaties, establishing central EU oversight of budgets, tax-raising powers at EU level, spending authority without the say-so of member state governments, the ability to raise Eurozone debt, and probably democratic mechanisms such as pan-EU election of a finance minister or a president.
The notion that Scotland would be voting for "independence" is thus a chimera. More probably the alternatives for Scotland would be to stay in the United Kingdom or to join the Single European State.
Note: I wrote the "alternatives for Scotland", not the "alternatives for Scots". Opinion polls suggest that Scots are unlikely to vote for "independence" – recent polls suggest it might be approaching two to one against. By contrast, the English are already more likely to vote to dissolve the Union, even in current polls. If Scotland were to achieve a "devo max" option of more devolution, the likely consequence would be an increased "if you don't want to be with us, then for goodness' sake go" attitude amongst the English.
In the final analysis, whether Scotland stays in the union is not purely up to the Scots. Believers in the Union should attempt to make Scots comprehend that we are not far from the point at which the rest of the United Kingdom may cease to want to be in a union with Scotland.