A myth is doing the rounds.

It is a figment at odds with the facts, but it suits the Scottish National Party and Unionists alike. This is the myth, elaborately crafted, of "Alex Salmond's independence referendum".

If you believe the myth you are liable to believe that in the autumn of 2014, or thereabouts, you will be invited to vote for or against a lot of things. At stake, supposedly, are currencies, oil resources, interest rates, taxation, monarchs, nuclear weapons, national debts, passports, regiments, broadcasting, EU membership and more besides. Dream it up and someone will be found to put your fears or hopes into words.

A small snag: none of it is true. Reasonably enough, the SNP want you to believe that a yes vote in 2014 would count as an endorsement of Mr Salmond's policies for Scotland. With equal zeal, Unionists hope to persuade you that a no vote would stand as a rejection of the First Minister and all his works. But a plebiscite is not a General Election. This vote, when it comes, will settle only one issue.

In one sense, of course, it is perfectly fair to talk about Mr Salmond's referendum: he more than anyone has secured Scotland's right to a vote. It was natural, therefore, that he would stand at the centre of yesterday's launch of the cross-party Yes Scotland campaign. That he has plenty of ideas for a post-independence world is, to say the least of it, no surprise.

You needn't hold the front page, either, for the news that Unionists will attack those ideas at every turn between now and 2014. That's what party politicians do. Amid it all, a simple fact endures: we won't be voting on a programme for government in the referendum. We will not be voting for or against the SNP, Labour, the Coalition, or any permutation of factions. That comes later.

Nationalists dearly hope, of course, that a yes vote will earn them a generation's worth of dividends. After all those decades of struggle, a big electoral reward should be in order. That doesn't make an SNP Government inevitable. It doesn't even mean that Mr Salmond would necessarily – the important word – be in a position to lead independence negotiations. A referendum victory could produce a few stirrings within his own party.

But let's not get ahead of ourselves. The important point is that in 2014 we won't be voting on, for example, an independent Scotland's relationship, if any, with the monarchy. We won't be deciding whether we can or should remain within Nato or the sterling area. The referendum is about the right to choose, not about the particular choices contained within anyone's "vision" of self-determination.

In his statements, Mr Salmond generally takes care to recognise this detail. Speaking at the Yes launch in a picture palace in Edinburgh's Fountainbridge yesterday, he said, "The people who live in Scotland are best placed to make the decisions that affect Scotland." He didn't add: "I therefore invite them to ignore my views on corporation tax, if that's how they feel." Such is the logic to which he (more or less) submits.

His Unionist opponents have no such scruples. Still struggling to come up with a coherent case for the United Kingdom, they are never done taxing Mr Salmond on what "his" independence would mean. Border posts? Bank of England control over interest rates? Bigger or smaller armed forces? Doom? Since the First Minister has a party to run and elections to win, he responds. That's when he forgets the small print: these things are not for him to decide.

Independence could be a Unionist's worst nightmare, or an administrative change so minor you would struggle to call it max. I happen to favour the former, but I get only one vote at a time. The ballot paper I return in 2014 won't get me a republic, or guarantee that the Trident boats are gone on the first tide, or even ensure that a future Scottish Government will be immune to neo-liberal nonsense. A yes vote will only – though it's a hell of an only – mean that such things become possible.

It sounds like a simplistic point. If so, this version of simplistic seems to be beyond a host of people involved in "the independence debate". The referendum could mark a profound and historic change, restoring Scotland to its place within the community of nations. It could equally mean no more than a rearrangement of the furniture and a couple of those economic levers for Mr Salmond to manipulate. An independent Scottish Parliament, however composed, will decide.

None of this means that a yes vote will carry no consequences. If a future Holyrood administration decided to explore the real meaning of independence there would be a satisfying amount of hell to pay. If such a government decided that Scotland should become only a kind of semi-autonomous dependency of England then a yes vote will have seemed, to some of us, like a wasted opportunity. When I hear Nicola Sturgeon tell Radio 4: "It's not about break-up, it's not about separation," I don't count myself inspired.

I know exactly why the Deputy First Minister uses such language, of course. I've heard enough about SNP tactics and the merits of gradualism. But I also know that it is not for the admirable Ms Sturgeon to say what independence is "about". Nor can any Unionist tell us that a yes vote will mean this or that, unless they happen to be guaranteeing vindictiveness on London's part. The book has yet to be written.

A long haul lies ahead. All bar the professional politicians will require reserves of patience in the months and years ahead, especially if we are to be subjected to relentless slanging thanks to a false premise. It shouldn't be complicated, yet few of those involved have any motive for keeping things simple. We are moving towards a referendum on accepting or rejecting the right to choose. The actual choices, even the economic choices, are matters for another day.

In that regard – not that it costs me sleep – Unionists do themselves no favours. David Cameron, Ed Miliband, Nick Clegg and all their Scottish colleagues are quick to say that "of course" the people are entitled to a referendum, and to a choice. Then they revert to type by maintaining that the choice really involves the euro, national defence, penury and your last chance to see your English auntie. Failing that, they attempt to turn the plebiscite into a referendum on Alex Salmond.

The First Minister would no doubt take on that campaign with enthusiasm, but the chance is not available. This isn't about him, as some of his partners in Yes Scotland have already begun to point out. Mr Salmond is smart enough to take the point, I think, and smart enough to convey it to colleagues and supporters in the SNP. If he wants one million signatures on a pre-emptive declaration, he needs as many fellow travellers as he can find.

I offer one tip to be going on with. There should be a few thousand signatures, at least, among all the old Labour types who used to support self-determination for every country in the world except their own. They should have noticed the contradiction by now.