For some time now, and especially since September 2014, the SNP administration in Edinburgh has been inspired by a single, powerful, notion: govern as though you were enjoying the early days of a newly-independent state.

Of course, Scotland is not - or not yet - an independent state and, for the time being at least, still has two governments, one in Edinburgh and another in London. But in attitude and demeanour, the SNP behaves as though independence has already arrived in everything except the formal recognition of that fact. This is a matter of mood and framing, for sure, but it's also something which has consequences.

It's why Theresa May's visit to Scotland and her meeting with Nicola Sturgeon today is a heavily symbolic matter. For some, this is Mrs May's first 'foreign' trip; for others, especially the miserably small-minded, it will be seen as a consular visit to a colonial outpost. This is all nonsense, but widely-believed nonsense.

I fancy many people were surprised to hear the new Prime Minister stress her Unionist credentials so prominently so early in her time in office: 'I believe with all my heart in the United Kingdom; the precious bond between England, Scotland, Wales and Northern Ireland. This visit to Scotland is my first as Prime Minister and I’m coming here to show my commitment to preserving this special union that has endured for centuries.'

And there, obliquely, lies the paradox: Scotland is both home and abroad, neither quite one thing nor wholly the other. The same but different and different but the same. This has often been true, but lately it matters more than it used to.

Mrs May holds to an expansive definition of Unionism, too. As she said the other day: 'I believe in a union, not just between the nations of the United Kingdom but between all of our citizens'. Here, as so often, you could hear the echoes of an old, old, tune. David Torrance, the biographer and journalist, observed that this was not so very different from how a Scottish Liberal Unionist put it as far back as 1912: 'Unionism meant not only the union of Scotland, England and Ireland, but the union of all classes...of the community in a homogenous whole.'

So we have been here before, at least rhetorically. But what does Unionism mean today? If that was a perilous question in 2014 it is even more generously stuffed with uncertainty in the post-Brexit environment.

Since that day of reckoning, Nicola Sturgeon has at least had a plan: present yourself as the wronged head of a wronged state. Scotland voted to Remain and so Scotland must Remain a member of the European Union. And to hell with the wider UK vote. So Ms Sturgeon scurried to Brussels for meetings with anyone she could meet and she convened a 'summit' of Scotland-based european diplomats to press the argument that Scotland was different and Scotland should be treated exceptionally. 'I have been absolutely clear on this issue' she says, 'the people of Scotland voted decisively to stay part of the European Union and their wishes must be respected.'

Except they can't be. All the talk of a 'reverse-Greenland' arrangement for Scotland is just talk. Scotland cannot be half-in and half-out of the EU. Not while it remains a part of the United Kingdom. It is in the interests of neither the UK nor the EU for Scotland to enjoy this kind of special status (whatever that status actually entails). Brexit means Brexit and the referendum result is clear. You can't reverse-ferret this and even if you could I am not sure the people of England would approve of a situation in which the Union was privileged above the result of the referendum. If the Jocks don't like it, they can go ahead and leave and do their own thing. This is one of the referendum's lessons too and the Union can be lost on the playing fields of Eton as well as in Scotland.

So there is an air of fantasy, of make-believe, about all this positioning. When the UK leaves the EU, Scotland will leave too (because, you know, Scotland is part of the UK). The best Sturgeon can hope for is an understanding that, should it ever happen, other EU states will look kindly on a Scottish application for EU membership and fast-track Caledonian entry to the club. That could, probably should, happen. If it comes to that.

In the meantime, it is evident that a Norwegian-style deal with the EU is evidently what all Scottish political parties - including Ruth Davidson's Tories - want. The less substantial the change, the better. That way we can at least pretend not so very much has changed.

But, inconveniently, the people of England have made it very clear they want rather a lot to change. Which means a hard Brexit, not a soft one.

That in turn leaves Scotland in an invidious position. Unable to control its destiny and yet also faced with the prospect that any alternative destiny will be as hard as it will be complicated. Expensive, too.

Suppose, for instance, Scotland marches off to independence and joins the EU. It will not be able to have its own deal with the rump-UK. It will be bound by the same terms of trade as every other EU country. If a hard Brexit means tariffs, then it means tariffs at the Tweed too. Which, given that Scotland sells four times as much to England as it does to the whole of the EU, is a whacking great problem. Were those circumstances to pertain, independence becomes even more expensive.

Scotland's interests demand a single UK market and a single European market. At present keeping both seems improbable, no matter which constitutional path is chosen.

And that has a psychological impact. Politics is not just about the nuts and bolts of economic self-interest. The 2014 referendum should have told us that and 2016's plebiscite supplied all the evidence even slow learners should have required.

The idea Scotland is being denied control over her future, denied the opportunity to make her own choices - for better or for worse - is a powerful recruiting sergeant for the SNP. And yet, unavoidably, that is where we are.

Mrs May faces an impossible test, then. If Brexit means Brexit she must - almost unavoidably - place greater strain upon the Union she says is such a precious thing. If Brexit means just a soft Brexit then she cannot fulfill her promises to the Leavers. These are close to irreconcilable interests and May can only pick one of them.

When push comes to shove, we know which she will choose too.

The economic arguments for independence are manifestly weaker now than they were in 2014 but it must also be acknowledged that the political argument for it is considerably stronger.

Which is also why the tragi-comedy that's the Labour party is also no laughing matter. The Conservative party needs credible opposition to restrain it from indulging its own worst instincts but Britain also needs a credible opposition to help maintain the ties that, still, just about, bind. That means Britain needs a Labour government at some point and preferably before it's too late. That's not enough on its own, of course, but a Britain in which the Conservatives rule for a quarter of a century is not a Britain that is likely to survive.

Asking Theresa May to lose the next election is asking too much, for sure, but it's another factor worth considering from time to time. If Britain is to mean something, it must mean a country in which all parts of the kingdom feel they have a stake. One-party rule is inimical to that.

I don't believe Nicola Sturgeon wants a referendum now or at any point in the next two years. Not least because it is not certain she would win it and, in any case, there is little enthusiasm for a fresh plebiscite in Scotland. But she wants one at some point, possibly as soon as the autumn of 2021 or the spring of 2022.

Now plainly much can happen between now and then and it is always foolish to assume current trends will continue indefinitely. Nevertheless, there is also no reason to suppose the SNP's current supremacy will end any time soon, nor that there will be a reawakening of British sentiment north or south of the border on Theresa May's watch.

Does Scotland privilege being in the EU over being in the UK? Probably not, at least not right now. But does it privilege being able to make its own decisions? Undoubtedly. And does it resent being forced to contemplate this kind of choice? Yes to that, too.