In 2013, the Scottish National Party claimed an independent Scotland would be the sixth richest country on earth. Like many extravagant suggestions, this contained the essence of its own downfall. It would be lovely if it were true but didn't it seem just a tiny bit too good to be true?
At the same time, and for the next 18 months or so, SNP politicians assured the Scottish people that there was no need to worry about the economic case for independence. They had the numbers to prove it. Granted, no one was ever encouraged to ask awkward questions about the assumptions made to generate this rosy-tartaned vision. For instance, what level of immigration would be needed to compensate for a population ageing more rapidly than the UK as a whole? Upon what basis, precisely, was the assumption of annual productivity growth over 20 years made? And, above all, perhaps, what if the cheerful predictions made about future oil revenues turned out to be mistaken? Those predictions deserve to be remembered. The Scottish government's preferred figures foresaw revenues of around £8bn in the first year of independence. Actual revenues? Essentially zero.
It's true that other forecasters' estimates also proved too optimistic. But none were nearly so optimistic as the figures promised by the Scottish government. Those estimates were, generally speaking, 50 per cent higher than those offered by anyone else.
And all the while we were assured, time and time again, that oil was not the basis of the Scottish economy. Why, it only contributed (in good years) something like 15 per cent of the total tax take. As Alex Salmond said, time and time again, 'We're on the cusp of a second oil boom'. Oil, Nicola Sturgeon assured us, time and time again, was 'a bonus'. Even as recently as last year, she insisted that 'The case for independence was never based on oil'. That is, I suppose, a point of view.
Awkwardly, Andrew Wilson, the former SNP MSP charged with leading a 'Growth Commission' to look at ways Scotland's economic performance can be improved, now admits what we knew all along: the SNP's economic forecasts were indeed based on oil. Far from being a happy bonus, oil was the lynchpin of the Scottish economy. The most important single part of the entire apparatus. If it fails; so does everything else. Not, it is true, to the point of making Scotland too poor to survive as an independent nation but undoubtedly to the point at which it begins its independent existence manifestly, measurably, poorer than it would if it remained part of the United Kingdom. Which means if there is a next time - and there may well be a next time - a different argument will have to be made. As Andrew Wilson told the BBC:
'We did have oil baked into the numbers and it was indeed a basis [for the economics of independence]. So I can say with some certainty in terms of our own work [in the Growth Commmission] that we'll assume for the purposes of our projections that oil is producing zero revenues and therefore treat any revenues that we get from oil as a proper windfall to be used on intergenerational projects rather than spent on spending today'.
I suppose I should at this point say that Andrew Wilson has been a friend for 20 years now and I cannot think of many nationalists for whose integrity and intelligence I have more respect. They'd be a better movement if more of them were more like Andrew. Saying this does not help him, I know, but there we have it.
Still, it comes as quite something when the admission of something we all knew was always the case becomes front-page news in just about every Scottish paper today. Mr Wilson is indubitably correct to note that 'the fiscal inheritance that we would have from the rest of the UK is a very difficult one' and that 'the economic circumstances are fraught at present'.
That makes independence even more, um, challenging than ever. The argument for independence is not just about economics but it's hardly unreasonable for Scots to consider fiscal reality when making their decisions. If that weren't the case there'd have been less need to make such a fuss about it last time; less need to assure us that independence would make us rich. That dog won't hunt anymore. The Scottish government's own figures prove as much. Which no doubt helps explain why it has now become fashionable to observe that the official GERS figures supplied by the Scottish government's own civil servants - the figures which, in a happier age, could be trusted as an accurate forecast of good times ahead - are no longer an accurate starting point for the independence argument at all.
There is something Orwellian about this. Then again, Doublethink has long been the nationalists' second-language. GERS were reliable in 2013 and 2014; now, when they show an alarming deficit, they are an incomplete and inaccurate estimate of the true state of the Scottish economy, spending and revenue. They only show Scotland as it is within the UK, not how it would be after independence. Things would be different then.
Well, they would have to be. Because taxes would go up and spending would come down. At least initially. The early years of the new state would be hard years. Better, though, to let at least some of the truth out now. The alternative, after all, is treating the people as though they must be fools. That can work, but it's a poor basis for policy, let alone a voyage of national self-discovery.
And yet, there is danger for Unionists here too. It is all very well and good saying 'You admit you lied last time, so why should we believe you this time?' but there is a distinction to be made between looking reality in the face and seeming to so thoroughly embrace uncomfortable news that you give the impression of welcoming, even relishing, it. There too, the line of reality between utopia and dystopia must be maintained. For everyone's sake.