They may decide to head out on their own, or they may choose to stay within the United Kingdom and be given as yet unspecified further powers to determine their own affairs.
Although the difference between those two choices might not be that great in the end, a separation following a majority Yes vote would be a significant set-back for the Union, Europe and the Scots themselves.
However, the debate could bring about some good.
As the nation states of the European Union head towards closer economic and political integration, its citizens are feeling that they are losing too much of their national identity and are therefore rebelling.
In some cases this manifests itself in protests against immigration, in others through the resurgence of regional and tribal issues, and in others again, in anger against Brussels ‘red-tape’ and the desire to win back powers for national governments.
The recent European elections gave an increasing share of the vote to the parties on the right arguing against immigration, citing the threat to jobs and criticising EU meddling in home affairs – as UKIP did in the UK.
In my view the real underlying fear is what in Germany we call Ueberfremdung, which translates as ‘foreignisation’.
That is linked not only to immigration, but also to overseas ownership of huge chunks of British industry, including ports, airports and utilities.
This is of course not just a British phenomenon. The same feelings are at the heart of the rise of populist right-wing parties in France, Austria, Greece and Spain.
The only countries that have reacted differently so far are Germany – my native country – and Italy.
Perhaps citizens in these two nations are not as easily reeled in by demagogues with simple messages because they have been there before.
Although the EU has talked much about the rule of subsidiarity – the principle by which decisions must be taken at the appropriate local level – Brussels has failed its member states by not delivering on it and by not making it clear enough.
The rising support for the ‘Yes’ campaign and ‘Scotland for the Scots’ is, I believe, an expression of similar concerns and must be taken seriously.
It is not good policy to try to scare the Scots about losing the pound and being economically worse off, or even by raising doubts about whether an independent Scotland could secure membership of the European Union, as Alex Salmond wishes.
This is much more an emotional issue and should be treated as such by the ‘No’ campaigners.
Far better, then, to concentrate of the positive aspects of the Union. There are not only economies of scale in business but also in politics. Size matters, as every business knows, when it tries to sell in global markets.
Paddling your own canoe economically and politically in a more and more globalised world is difficult, to say the least. The threat of Britain leaving the European Union is similarly counterproductive in my opinion.
Most importantly, the men in Brussels and Angela Merkel in Berlin must have a close look at the results of their actions so far. In the long run they can’t ignore the deep seated fears and mistrust of the peoples of Europe.
Britain may appear isolated following the row over the appointment of Jean-Claude Juncker, but should continue to lead a push for change.
As for Scotland and the UK, the West Lothian Question – whether Scottish, Welsh and Northern Irish MPs should be able to vote on matters involving only England – is unresolved, and the relationship between Scotland and the other countries that make up the Union is not very efficiently structured.
It might be an idea to take a look at the constitution that the Allies gave Germany after the last World War, which has a clear separation of national, state and local powers. It could serve as a model for the men in Brussels.