Iain Macwhirter: The timing of the referendum is the biggest decision Nicola Sturgeon will ever make

Few doubt that there will be another independence referendum at some stage. The material circumstances have clearly changed since 2014, following Brexit, and Scotland and England are moving further and further apart politically – not least because of Labour’s civil war which could leave the Tories dominating Westminster for the next decade. Some, like Alex Salmond's former chief of staff, Geoff Aberdein, are confidently predicting that there must and will be an independence referendum “within the year”. Others, some of them very close to the First Minister, are predicting precisely the reverse – that she has no thoughts of going for broke until the Brexit fog clears.

The pro-independence camp, which includes prominent Yessers like the writer/musician Pat Kane and 10s of thousands of activists, believe there will never be a better moment than right now. Brexit has shredded the unionist argument that a vote for independence is a vote for isolation – from Europe and the UK. Scotland is being dragged unwillingly out of the EU with untold economic consequences. There is no “caring, sharing” unionist status quo any longer. Gordon Brown, who was back last week proposing another round of devolution, seems like a figure from history.

Support for the SNP is at historic levels – the latest YouGov poll on Friday had the SNP back up to 52 per cent on the constituency vote. But many activists fear that it can only fall in future through the laws of political gravity, the longer the party is in office. Support for independence is up also on 2014, marginally, at around 47 per cent Yes, to 53 per cent No, according to Professor John Curtice. And while this may not be “clear and sustained evidence that independence has become the preferred option of most Scots” – as Sturgeon put it in May – it is headed in the right direction. Look how much support for independence increased during the last independence referendum campaign, say the go-for-it tendency. The iron is still hot: strike it.

Others, like the former SNP cabinet minister, Alex Neil, want them to cool off. Staging a referendum while the nation is still confused and perplexed by Brexit is foolhardy. Asking people to cut off from the UK, when they have yet to learn what breaking from the EU means, is to invite a negative response from scunnered voters. People are fed up with referendums – two in two years – and need a moment to reflect on where they are – and where the hard borders will be. Once it sinks in that Brexit really does mean that Britain is leaving the EU, voters may be much more receptive to the argument that independence is the only way back into Europe.

Moreover, you don't have to accept the GERS methodology to realise that the Scottish economy currently is in a bad way because of the collapse of the oil industry. It's not the end of the world, and many small countries do extremely well without any oil at all – and cope with large deficits. But there is a profound structural change taking place in the Scottish economy right now which makes it very difficult to frame a convincing economic case for independence. Nor is this uncertainty helped by the fact that the Scottish National Party is undergoing a review of its policy on the currency of an independent Scotland – the key issue on which the 2014 referendum turned. History is going the SNP’s way, say the ca’ canny tendency: don’t blow it.

Those counselling caution seem to be winning the First Minister's ear right at the moment. But the Scottish National Party is not one that thrives on caution and baby steps. It is a movement that wants to change history, and thrives on bold initiatives that get the blood going. The independence referendum campaign was, for many thousands of people in the Yes campaign, a transformative experience – politically and psychologically. It was an almost revolutionary moment that ignited the fire of political imagination and after which anything seemed possible. Voter registration at 97 per cent: the highest turnout in electoral history. Who wouldn't want to relive that experience?

Never before in Scottish history has there been an independence movement like it. Almost overnight, 1.6 million people in Scotland decided that they weren't going to listen to Project Fear. Scotland surprised itself in 2014. It realised that it wasn't just a region of a declining post-imperial power, but a nation in its own right with new possibilities. The centre of gravity of Scottish politics shifted from a default if reluctant unionism, to an assertive, if strictly civic, nationalism. The aftershock was the Tsunami general election of 2015, when the unionist parties were obliterated.

Scots already are, to use the cliché, “independent in the mind”. But it is quite possible to be confident about Scotland's future independence and still be highly cautious about the process of becoming independent. Scotland is a nation with a very long and turbulent history and Scots know from bitter experience that when they indulge in confrontation with their more powerful neighbour they are inclined to come off worst. This has not been an issue for most of the last 300 years because he Union – whatever people think of it now – was in its time an achievement of Enlightenment statesmanship.

The Union ended 400 years of almost constant warfare by giving Scotland – or at any rate the Scottish elite – a stake in the emerging British Empire. That's history now. The alliance of convenience between Scotland and England in the Union no longer accords with either nation's interests. Yet Scotland finds itself left umbilically linked to a post-imperial and increasingly isolationist UK defined by financial interests in the City of London and by a Conservative-dominated Westminster.

The process of disengagement from the UK is already advanced. The policy of incremental independence begun by Alex Salmond in the 1990s has been extremely successful. Scotland has already gone most of the way to independence without a hint of violence or civil unrest. A major step was the formation of the Scottish Parliament in 1999, which largely restored political autonomy, at least in terms of domestic legislation. Since then, Holyrood has acquired a range of economic powers which fall far short of economic autonomy, but could have provided the basis for a functionally independent Scotland located within the UK.

But Brexit threw a spanner in the works. The SNP’s over-arching policy of independence in Europe presupposed that the UK would remain in the European Union. Within that context, Scotland could have attained a form of independence through evolution, which would have allowed it to remain both part of the UK and part of Europe. That project, outlined in the 2013 White Paper On Independence, may no longer be viable. Indeed, incrementalism – independence by stealth – may have reached its limits.

Of course, this doesn't mean a full-frontal assault is the only way. What may be needed is a re-engineering of the independence project. In addition to the bedrock economic argument, the SNP needs to work through its attitude to globalisation to redefine independence. The extraordinary events in Ireland, where the government has had to appeal against receiving £11bn in back taxes from Apple, shows the problems faced by small countries dancing with big business. Should Scotland emulate Ireland as some neo-liberals propose, and become a kind of Caledonian tax haven? Or should it continue to emulate the social democratic Scandinavian model, complete with high personal taxation and a big state?

Should Scotland automatically seek to return to the European Union, which doesn't appear to be very interested in the welfare of small countries, like Greece, with large deficits? A broader question which the SNP listening cadre will hear asked on the doorstep is whether independence should take precedence over addressing Scotland's lingering social ills, revealed so starkly last week by the Scottish Index of Multiple Deprivation. Last year saw the biggest annual increase in mortality figures in Scotland since the Second World War: 8.5 per cent. Is the NHS sound enough to cope with the shock of independence?

With all these questions swirling around, Nicola Sturgeon could be forgiven for having sleepless nights. Fortunately, she isn't. The one thing we know about the First Minister is that she has an astonishing capacity to sustain pressure, as we saw during the independence referendum and the UK general election when she was subject not only to abuse on social media but sustained attack from the combined forces of the UK media and political parties. One thing she isn't going to do is be bulldozed by over-zealous party activists into making a futile if glorious bid for national freedom. She is a utilitarian nationalist, and doesn't go in for romantic consolations of heroic defeat.

Nicola Sturgeon's listening exercise – the biggest consultation in the party's history – is of course a delaying tactic: something to keep the activists engaged without actually committing them to a full-scale campaign. The consultation, announced last week, will expose the more gung-ho nationalists, who largely exist in a social media echo chamber, to the large number of Scots who don’t want independence, at least not yet.

But the new national conversation isn’t an exercise in time-wasting. The SNP is very good on the doorsteps, as anyone who has followed them canvassing can confirm. They have a legion of 120,000 motivated and highly persuasive members who will be putting the case for self-government directly to the people who are most in need of persuasion: the older and more middle-class Scottish voters who avoid social media, think JK Rowling is a national treasure and believe the SNP are a bunch of mad cybernats. They will be doing so against the background of Britain's chaotic disengagement from the European Union led by mad Brexiteers.

My own view is that the opinion polls underestimate the extent to which Scots of all classes have begun to take independence seriously as a practical project. The euthanasia of the status quo has changed the game. Brexit has all the makings of an historical watershed. A UK dominated by rightwing anti-Europeans, obsessed with immigration and deluded by echoes of empire, has undermined lingering moral attachments to the Union. The process of disengagement from Europe will be a long and trying one in which Scotland's interests will be repeatedly set aside. There is no downside here for the independence movement and no conceivable political threat from Labour or the Tories. So this is probably not be the time for an early referendum.

Then again, it very well could be.