Vote No for confusion and uncertainty.

That is hardly likely to be the clarion call from Alistair Darling, leader of Better Together, as he makes the case against Scottish independence in the long build-up to next year's referendum. Yet there is a cogent case to be made that a No vote would lead to far more uncertainty than a positive Yes vote.

There are several reasons for thinking this. The other day I heard a respected expert on European affairs enunciating the following feasible and plausible scenario. Next September, Scotland votes No. The following summer, in the UK General Election, David Cameron is voted back into Downing Street, albeit with a small majority. True to his promise, he holds a UK-wide referendum on Europe in 2017.

The decision is to leave the EU. When the results are broken down, it is clear that England has voted to quit Europe by a significant majority, but Scotland has voted to stay in Europe by an equally significant majority. In these circumstances, the case for a second Scottish referendum on independence would be very strong indeed. In any event, there would be loads of uncertainty, dollops of confusion. Tensions between England and Scotland would be acute.

There are several "ifs" in that scenario, but the present UK political scene is more volatile and kaleidoscopic than ever. It is surely false to suggest that a No vote in the Scottish referendum would serenely lead on to a period of settled stability. It is now clear that the Unionist parties in Scotland all want more devolution; some of them want much more. Even the Tories, under Ruth Davidson, who when she became leader seemed to be adamant against any further devolution, are late converts to the cause. The Unionist parties will be vying with each other with proposals for devo max, devo max max, devo supermax and goodness knows what else. If this isn't a recipe for constant uncertainty, I don't know what is.

The other point is that a narrow No vote in the referendum, with the Yes side falling short, but not by much, could lead to perfectly valid pressure for a further referendum, sooner rather than later.

I know that in Quebec, Canada, a narrow rejection of separation did, in a similar referendum, appear to put the matter to rest. But Scotland is different in that the rise of Nationalism as a credible political credo has been steady and relentless. Even so, at every stage the Scottish National Party has been underestimated. How many people can honestly say that when they surveyed the results of the first Scottish Parliament elections in 1999, when Labour won 56 seats to the SNP's 35 (though this was not enough for an overall majority), they could foresee that in a dozen years the SNP would have gained enough seats for a comfortable majority at Holyrood?

The key fact is that the devolution settlement of 1997, presided over by Donald Dewar, gave the SNP the chance to move convincingly from being a fringe party of protest to a mainstream party of potential power. That opportunity has been seized, smoothly and deftly.

The various key momentums, the substrata undercurrents, in Scottish political, social and cultural life are flowing and will continue to flow in the Nationalist direction. This means that the Better Together campaign – which I concede currently looks like winning – is a bit like erecting a temporary dam to control a river in ever-growing spate. I'd say that to the constructors of that dam: Beware of shoddy workmanship – your dam needs to be very strong and exceptionally well built. You need a squad of united and industrious workers to build it. Enough said.

To return to where we started. A Yes vote would provide certainty. Of course there would be a large amount of detail to be sorted before the first General Election in an independent Scotland. And I know that's where the devil resides. But at least the overall context would be one of absolute certainty.