The politician-turned-psychic is a dangerous creature that should hasten a rush for the alarm bell. There's an Orwellian unease about a fearless political prediction that's usually based on an assumption of control of the present, and too often a gross rewrite of the past. Criticism of the prophet's accuracy is dismissed as a petty inconvenience for those holding unquestionable trust in their sage.

So, when the fog cleared from his crystal ball last week, Scotland's ductor primoris, Alexander Elliot Anderson Salmond, held nothing back when he revealed Scotland would be fully independent by 2017.

Yes, we have been here before. "Free in 93" was a decent SNP election campaign slogan that could, almost, be wheeled out once a decade. However, 2017 is a different kind of target.

With premier Salmond and the nationalists now running the Scottish Government this isn't just another Groundhog Day prediction of the end of the union. Salmond can't be dismissed as the Caledonian equivalent of Punxsutawney Phil, offering his instinct-driven prophesy and then disappearing underground while we wait to see if the forecast is correct.

Making 2017 happen requires pro-active nationalist politics and one that ditches the comfort zone for those still wanting to believe the SNP's prime objective is, first, a display of parliamentary competence in Holyrood with the longer-term objective of independence waiting off in the distance. Alexander the Sage's 2017 prophesy points to an independent Scotland being the over-riding objective at the centre of everything the SNP do. Independence within a decade says they have no-one in their waiting room.

Salmond doesn't usually do dates. He does, however, do time. He once told me 20 minutes was all it usually took him on a plane between Heathrow and Glasgow to convince a stranger of the merits of an independent Scotland. But that's too many air fares to constitute a viable political strategy for his 2017 target.

To scupper the union within a decade, two things must happen. The English must rapidly increase their resentment of the Scots and what Scots benefit from the post-devolution settlement; and the Scots have to increase resentment of the English and the way England is thought to hold back the oil-rich economic potential of an independent Scotland.

This recent questioning of the merits of the 300-year-old union was not begun by Salmond, or his party, or the small minority of Scots who support independence. Margaret Thatcher and 18 years of Tory government did that job pretty well. And what Thatcher started, Salmond thinks he can finish.

The England side of Salmond's to-do list is advancing nicely. The Daily Telegraph's reactionary nerve-ending, the columnist Simon Heffer, last week proclaimed "the Union, like the empire, is over". The "Scottish Raj" in Westminster was illegitimate; Britain was now a geographical rather than a political term, and England and Scotland can only now be happy if they are politically apart.

The applause from Carlisle to Land's End in the Telegraph's blogosphere was deafening: they reason the Scots in Heffer-Heffer-land are trousering cash taken from English taxpayers to pay for better healthcare, better schools, free university education. Yet, anything that might contradict such a view - NHS waiting lists in England and Wales will soon hit the 18-week maximum, a target likely to be missed by NHS Scotland, even by 2011 - is glossed over.

In Scotland the first budget of the SNP administration and the abandonment of manifesto commitments - on university funding, student debt, school class sizes, drug rehabilitation budgets, affordable housing, police numbers - should engender scepticism over SNP promises. But, if the 2017 date arrives as Salmond predicts, none of this can be allowed to get in the way. Broken promises are, therefore, not the Scottish Government's fault but Westminster's parsimony.

The key manifesto commitment, however, remains the promised referendum on independence. It is Salmond's timing on this that drives the advance towards 2017. He knows he cannot deliver a referendum inside this parliament, one he would lose anyway.

So, come the eve of the next Holyrood election campaign, Westminster, not the majority of MSPs in Edinburgh, will be serially portrayed as the institution denying the Scottish electorate their democratic right. The solution? Would not a strong, majority SNP government be able to deliver a referendum and put right all the Westminster-inspired failures of the past 11 years? Win in 2011, and Salmond's prophesy comes closer.

Salmond and Conservative leader David Cameron at the moment share a common cause. The long-held Tory commitment to limit the power of MPs from Scottish constituencies and create a parliament-within-a-parliament by introducing "English votes for English laws" would not just draw blood from Labour in England, it would utterly change the wider Scottish electorate's perception of the union.

Scottish MPs at Westminster would become ambition-limited second class members. Hold an independence referendum against this political backdrop and the current majority support for the union will shrivel - exactly what the oracle at 6 Charlotte Square might pray for, although private talks last week between leading English Conservatives and senior figures from the SNP suggest more than petitionary prayer is being discussed.

Sir Malcolm Rifkind's recent role in highlighting Tory plans to curb Scottish power at Westminster as a solution to the West Lothian Question, might not be all Salmond is hoping for. As a resident of Inveresk, Sir Malcolm's East Lothian solution contains its own inconsistencies.

If the Tories win the next election and control the UK parliament and hold a majority of English MPs, why would they waste parliamentary time with the aim of seizing control of something they already control?

So, how reliable is the 2017 prediction? That depends. There are fanatical millenarians who believe the millennium signals the end of the world. So why are we all still here. Didn't 2000 pass uneventfully? Not if you believe the calendar was fixed.

Iain Macwhirter is away