What happens if the Scots vote yes and no?

After the West Lothian question and the Gazza question, the Gordon Brown question: How come the Scots are apparently delighted to have a Scottish chancellor running their tax affairs from London when they aren't at all sure they want one doing the same thing in Edinburgh?

As referendum day creeps ever closer, so do the opinion poll findings on whether the voters want their new parliament to have tax-raising powers. About two-thirds of them want the thing established, apparently, but one poll at the weekend suggested only around 45 per cent want it to be able to change the basic rate of income tax.

So, the possibility of a yes-no vote on Thursday has become a real one. The Gordon question must be answered. (For those who have forgotten, the West Lothian question is the one about how Scottish MPs get to vote on English matters when the English can't vote on Scottish ones. The Gazza question is about how an Englishman living in Scotland gets a say in the referendum while a Scot living in England doesn't.)

There is still every chance of a yes-yes vote, of course - at the last count there were still more in that camp than any other. But it is time to ask why support for tax powers seems to be faltering.

The leaders of the Think Twice campaign will tell you that a tax-raising power would be bad for Scottish business; that it would drive companies south of the border. What they are really saying, though, is that these companies would be forced to follow the talented Scots who would leave in droves rather than pay more for a better road system or shorter hospital waiting lists.

A yes-no vote this week would be a sign that while the Scottish people have embraced the romantic notion of devolution, they have not even begun to come to grips with the reality. After all, the tax-raising power on offer - 3p either way on the basic rate of income tax - is an extremely limited one. If it were levied in full, someone earning pounds 15,000 per year would pay pounds 17 per month extra in tax. Besides, the parliament could put taxes down rather than up if it chose to do so, and in any case it would probably not do anything to them at all before the next general election. Even this, it seems, could prove too much for the cautious Scots.

So, what will they get if they cannot bring themselves to risk paying a few pounds more each month for better public services? They will get a body which, in one crucial respect, has less power than the local council with which Tony Blair famously compared it. A Scottish parliament with no tax-raising powers would have to argue its case with Mr Brown if it wanted more money for schools. But if Strathclyde Council wanted more, it could simply put up the council tax.

In a further humiliation, the parliament would be able to hand down new tax-raising powers to local authorities while barred from making such charges itself. Thinking about a tourist tax? That will be one for the Highlands and Islands. Holes in the school roofs in downtown Dumfries? How about a local rainproofing tax?

The taxless Scottish parliament would still have a number of significant powers, of course. It would have control of the health service, schools, housing, the environment, sport and agriculture. It would be responsible for both civil and criminal justice, and it would control economic development along with financial support to business and industry. But it would not have any control over its own purse-strings. The parliament's main job would be to receive a sum of money from Westminster each year and to decide how to distribute it. If more money was needed for housing, hospitals might have to suffer. If tougher anti-crime laws were on the agenda, money for new prisons might have to come from the education budget.

The flip side of these restrictions would be that the MSPs, or Members of the Scottish Parliament, would be left with a perfect scapegoat when their electors complained. Perfect, of course, because it is all too familiar: blame the English. If there isn't enough in the pot, it will be Westminster's fault. In fact, it will be Gordon Brown's fault. So the answer to the Gordon question, in short, is that the Scots won't be so keen on a London chancellor when they realise his decisions are binding their hands.

One yes-yes campaigner said yesterday that a no vote on the tax question would leave behind it nothing more than a talking shop - and a talking shop with a pounds 40m start-up price tag to boot. But it would be worse than that. It would quickly become a little nest of resentment against the Treasury, with Labour figures joining their opposition colleagues in condemning government spending decisions. This could only mean that Scotland's desire for a grown-up political system would be thwarted. Instead, it would be left with the "not my fault" playground rhetoric that has characterised it for so many years. In response, the English would probably wonder aloud why their taxes continue to pay for public spending north of the border at 14 per cent above the UK average.

Once the deed is done and the parliament is up and running, there is no way back. If its limitations lead people to see it as impotent and resentful, there will be only one way to put things right: to go on towards greater independence. That, of course, could mean a belated decision to go for tax-raising powers, or it could mean something more. On the other hand, it could mean hobbling on indefinitely with neither real power nor real respect.

All these arguments come to nothing, though, when compared with the central question that Scotland will answer on Thursday. Do the Scots really believe they can run their own affairs? All this boils down to is a simple issue of democracy. For years, people north of the border have been complaining of taxation without proper representation. Surely now the time has come for them to accept that they cannot have real representation without the possibility of taxation.