COULD I introduce you to a man called Walter Macfarlane? I have to admit, I had no idea who he was until a few days ago, but I now can’t get him out of my head because of something he said about Scotland and the Union. It got me thinking about the beliefs of nationalists and unionists, but, more importantly, it got me thinking about facts more generally. Facts – in case the President of the USA is reading this – are things that are known or proven to be true and we need more of them, surely – lots more of them – especially in the debates about Brexit and Scottish independence.

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So, in the spirit of trying to encourage more facts in a post-fact world, could I offer you four which I think we can rely on? I realise, of course, that some people will immediately look at my list and say they’re not facts at all, they’re opinion, but all I can say is that this is a genuine effort to distil the last few days of argument over the SNP, Nicola Sturgeon and the Alex Salmond investigation into four areas where I think most of us could find agreement. Here goes.

The first one is this: the Salmond investigation is unlikely to change many minds on independence, which is where Walter Macfarlane comes in. Walter, I should explain, has been dead for 250 years but I only came across him for the first time a few days ago while I was reading the journals of the great Scottish diarist James Boswell. Boswell writes about meeting Macfarlane in the entry for Sunday 21 November 1762 and describes him as a man who was “keenly interested in the reigning contests between Scots & English”.

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“He talked much against the Union,” writes Boswell of his new friend. “He said we were perfect underlings, that our riches were carried out of the country, that no town but Glasgow had any advantage of trade by it, and that many others were hurt by it.”

Why am I bringing this up now? Mainly because it demonstrates something that’s often forgotten, which is that unhappiness with the Union and support for independence is not a modern phenomenon, and it’s not all about the SNP either. As you can see from Boswell’s diary, Macfarlane was complaining about the Union just 60 years or so after the Act of Parliament that brought it about and 170 years before the SNP was even thought of. Which is the important point: independence has always been a strand of Scottish opinion and, seen in that long historical context, the travails of Nicola Sturgeon (real as they are) are unlikely to greatly change that one way or the other.

The second fact is this: the Salmond investigation has emphasised that there are serious divisions in the SNP. Some nationalists appear to be offended by this idea and deny there is any division at all but the briefings of Salmond supporters against Sturgeon and vice versa speak for themselves. In fact, even as he made an apparent appeal to end the acrimony at the weekend, Alex Salmond couldn’t resist turning his handshake into a punch. He said he had ordered his team not to become involved in any more exchanges before criticising Sturgeon for not concentrating on independence. There may be some in the SNP who insist this doesn’t represent division but then Baghdad Bob insisted there were no American troops in Iraq to the sound of American troops in Iraq.

The third fact leads straight on from the division in the SNP but is about nationalism more generally and it’s this: levels of support for both sides of the independence debate have not shifted.

In some ways, this third fact is the most surprising of all because, on the face of it, the circumstances are in place for a breakthrough on either side. For the opposition parties at Holyrood, there’s the Salmond investigation and its implications for Sturgeon and yet support for the SNP has not changed, and for the nationalists, there’s the crisis of Brexit and yet the polls continue to show 55 per cent of Scots want to remain in the UK. The nationalists may talk about a “surge” and the unionists may revel in the SNP’s crisis, but the polls haven’t changed. That’s a fact.

Which leads us to the fourth, final, and perhaps most controversial fact: a second referendum on Scottish independence before 2021 is less likely than it was two years ago. Partly, this is because of those polls again (the SNP’s hopes for a rise in support for independence on the back of the 2016 vote for Brexit have not been realised) but it’s also because of the logistics and timing. The reality now is that we may not know – even by 2021 – what Brexit is going to look like and Sturgeon herself has said there will be no announcement until the fog has cleared. Then there’s the clincher: there is no prospect of a Section 30 order giving permission for a referendum from the Conservative Government. That’s a fact many of those in the independence movement simply pretend does not exist.

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The effect of all of these facts, as I’ve confidently called them, is another matter entirely and depends on how much the politicians resist them. In the wake of the Salmond investigation, it’s certainly hard to imagine the SNP fighting the 2021 election campaign with any of the confidence it had in 2007 and 2011, and even in 2016, but then again there’s every chance Nicola Sturgeon will stick to the grid and announce a referendum before 2021 in the hope that its rejection by the UK Government will increase support for her position.

Should that happen, I have honestly no idea if the strategy would work – the facts don’t stretch that far – but maybe now would be a good time to return to the diaries of James Boswell for some insight from the past.

Writing on 11 December 1762, just a few days after his meeting with Walter Macfarlane, Boswell got to thinking about the upheavals caused by unrest and war. He did not much care for the quarrels of Mankind when divided into particular states and nations, he wrote, but he could see that they depended not on facts but on the frailties of humans. “I can see that Great People, those who manage the fates of Kingdoms,” he said, “are just such beings as myself.”