You will recall that, according to the greatest account of England's history, every time the English thought they had solved the Irish Question, the Irish changed the Question.
Something similar afflicts David Cameron's grapplings with the Scottish Question. The poor man is damned if he does and equally damned if he doesn't. The other week he was lambasted for his effrontery in giving a speech about Scotland in, of all places, London. Today he is lambasted for bringing his cabinet to Aberdeen. How dare he lecture us from afar; how dare he venture north like some touring proconsul!
The optics, as the pros say, are not very good for the Prime Minister. The cabinet very rarely comes to Scotland. Drawing attention to that fact may not help Mr Cameron's cause. It risks reinforcing precisely the negative stereotype he seeks to counter. (On the bright side: at least it's not, say, August 11th.)
Moreover the ground upon which the British government chooses to fight today may not be the best terrain imaginable. There is, to be sure, something to be said for attacking your opponent's strength. Beat him there and you defeat him everywhere. Even so, it is a bold move. North Sea Oil is Scotland's economic strength and, frankly, the industry that makes independence conceivable.
Oil accounts for something like 15% of Scottish GDP. As problems go, this is one of the better ones to have. Granted, this means that onshore GDP per capita is lower than the UK average and this too highlights the extent to which an independent Scotland would, at least initially, be awkwardly dependent upon oil revenues. Even so, this is a problem most of us would rather endure than not (the exceptions being Green crackpots who wish to leave the oil where it is).
It may be, as Douglas Fraser has suggested, that a British government would be better placed - by virtue of not being so reliant upon oil revenues - to enforce the kinds of reforms to the industry suggested by Sir Ian Wood but, frankly, even if true this is a hard thing to sell politically.
Because, whether the British government means to suggest this or not, it leaves Westminster arguing that, in the end, Scotland is too small and too weak to manage the oil industry. At least that is the implication of the latest iteration of the now-familiar security argument in favour of the Union. Again, there is something to this: pooling resources is not necessarily daft; Scotland would be much more vulnerable to swings in oil prices than the UK is at present. As Larry Elliott remarked yesterday, this is classic boom and bust territory.
Be that as it may, the suggestion that Scotland would make a balls of the oil industry is one that will strike many Scots - not all of them committed Yes voters by any means - as something that is inherently daft. They don't want to believe this and many of them will not believe it. To put it bluntly, we are not Azerbaijan but if Baku can run an oil industry perhaps we can too.
True, the Unionist case is a little more nuanced than sometimes suggested. It is not that Scotland could not manage life as an independent nation state but that its interests are better served by the Union. Quite Good Apart but Better Together.
Perhaps the Prime Minister will succeed in persuading swithering Scots that the oil is too complicated, too uncertain and too important to be left to an independent Scotland but, on the face of it, I wouldn't want to wager too hefty a sum on that proposition. Not least since not everyone will be convinced Britain has used its oil revenues as effectively as it might have.
It's Britain's oil, of course, not Scotland's. At least for now. But for how much longer?