“Can a man not have a dream?”

When my pro-independence brother Andrew said that to me, it was the moment when I knew. When I knew I could not win the argument; when I knew the No campaign can never win the argument even if they win the vote; when I knew that no matter what happens in September there can be no going back to the way things were before.

It wasn’t meant to happen that way when two brothers, two sons of Fife, sat down to discuss the pros and cons of Scottish independence.

I sat in the red, white and blue corner: a pro-union, England-based political theorist, imbued with the over-confidence that afflicts many older siblings.

In the blue and white corner sat Andrew: a firefighter from Dunfermline who has read as many books on politics as I have tackled burning buildings.

O brother why art thou …?

The early rounds were tentative, if predictable. I rehearsed the now-familiar Better Together arguments, enhanced by the recent interventions of David Cameron, George Osborne and José Manuel Barroso.

We have 300 years of shared history in which Scots have achieved greatness as part of the political partnership we now call the United Kingdom. Twice in the last century, challenges to the UK’s very existence emerged on the continent.

If things ever get that bad again would a Scot prefer to be standing alongside a Geordie, a Scouser and a Cockney; or a Belgian, a Spaniard and a Frenchman?

Then there is the pound. Scotland could never be truly independent if monetary policy is ultimately determined in London by the Governor of the Bank of England. The American political scientist Harold Lasswell’s aphorism that politics is about who gets what, when and how, is a reminder that the person who holds the purse strings ultimately holds the power.

Complicating matters further, the President of the European Commission has warned that a Scotland that cedes from the Union also cedes from the EU. Spain is desperate to prevent secession by the Basques and Catalans and has made clear that it will veto any Scottish application for membership of the EU or the euro. No precedents allowed.

Yet none of these setbacks has remotely dented Alex Salmond and Nicola Sturgeon’s capacity to brass-neck their way through the obvious financial and political pitfalls.

The power of dreams

But then came the moment of truth in our conversation: “It’s not about Salmond or the SNP. It’s about the dream. Can a man not have a dream – to run your own country in your own way?”

That’s when it became clear. The Better Together campaign has been emphasising nuanced technicalities, marginal financial benefits, additional oil industry investment, institutional problems and European politics: all reinforced by an appeal to a common heritage. A common heritage that tries to gloss over inconveniences like the poll tax.

For the pro-independence Scots – not only SNP voters but some Scottish Labour, Conservatives and Lib-Dems as well – it is about a dream. Which is why a No vote on 18th September would represent not the end of the independence “problem”, from a unionist perspective, but the beginning of a new one. Because there can be no return to the status quo.

Legally and constitutionally it might be feasible. Expected even. But it will not be possible to govern in the same old way if between one third and a half of Scots have had their dream snatched away.

Crunch for Cameron

So what should be done? If David Cameron has not dangled the Devo Max consolation prize in the lead-up to the referendum, then he may need to offer it immediately afterwards in the event of a No vote. A previously unthinkable degree of Scottish political and fiscal autonomy might be enough to maintain a stable political union.

However, such a degree of autonomy would magnify the West Lothian question. MPs from an increasingly autonomous Scotland should not expect to vote on any English matters at Westminster. The result could be an Ed Miliband-led London government with little or no mandate to govern England.

Salmond’s arguments on both the European question and the currency position currently boil down to what we do or don’t know about what may or may not happen. All presented with supreme confidence that every outcome will favour the nationalist position.

But the No campaign can bombard the debate with facts, figures and scare stories, and in that way pro-union Scots might win the vote. What they will not do is win the argument because you can’t defeat a dream at the ballot box.