I've been thinking a bit about this thread. The right to national self-determination is an absolute one, and if the people of Scotland clearly want this then of course it must happen. I do think it should be a clear majority over a period of time for such a massive change - say polls showing 55%+ for some years and a referendum which gains 55%+. In the end it is a decision which once made cannot be undone.
I'm pretty certain that after sober refletion the people of Scotland will vote no:
* The economic case will be explained not by the SNP but by the IMF, and will be shown to be so bad that the idea is a non-starter.
* A part of a sovereign state that becomes independent must re-apply to join the EU, and needs consensus from all EU nations. Spain has said that she would veto - presumably reflecting concerns in Spain around regions breaking away. Possibly Italy and even Germany would think in the same way. The EU is about union not division and is presently putting its weight behind keeping Belgium intact (not prompting the fractious Belgian politicians to allow the Flemings a regional assembly so Belgium can at last have a government).
* It is far from clear that the people of Scotland want the additional powers Scotland would have as a sovereign state. Scotland would have its own foreign policy, defence policy and army, and a right to issue its own debt to balance its budget (but at much higher rates than the UK). I don't think people in Scotland actually want these powers. What do the people of Scotland really want that they do not now have?
* The USA will have a view on Scottish independence - just as they have a view on Quebec independence.
I've also thought that it is about time the constitutional framework of the UK is revised, and maybe a Scottish independence referendum should prompt that. The perfect solution IMO would be to grant Scotland complete control of domestic policy along with fiscal policy (within pegged parameters) while Scotland remains on sterling, possibly even on a floating peg. Scotland has its own judiciary. The armed forces might be more clearly divided (if this is an issue within Scotland).
There is a pressing need to resolve the West Lothian Question. Now of course an independent Scotland would solve that at one go - and give an in-built Tory majority for the UK. Alternatively I think we need some revamped and empowered Council of the Isles as a more flexibe framework for the four home nations, and including the Isle of Man and Channel Islands (and probably Gibraltar). I think there is little doubt that Ireland, like it or not, will need further UK support to get out of their financial mess (yes I know they won't like it), and a revised concept of a Council of the Isles might be the umbrella to do this. The key would have to be to find a structure where all parts of the Isles feel they have ownership.
Maybe we should all see the debate around an independence referendum in Scotland as a great opportunity to come up with something better than what we have now. I would go as far as to say I don't truly understand what "independence" means in this context - geography means that Scotland will always have to deal with England, and always have the overwhelming majority of its exports either with England or through England. If Scotland wants independence, fine lets use this word, but it has to be modified so that the debts are not split (bankrupting Scotland) and so that Spain and others don't kick Scotland out of the EU. The people of Scotland deserve their prosperity (and should not believe the fibs the SNP is telling), prosperity which they are not going to get if they take "independence" to its logical maximum. And for that matter England deserves not to have a bankrupt state on its border which (like Greece is doing) becomes "ungovernable". How would England cope with the flood of migrants? Border controls at Berwick and Carlisle? (And for that matter what happens to Berwick? - is it England or Scotland?) We've just seen border controls reintroduced between Italy and Spain, and we already have police checks between Great Britain and the whole island of Ireland.
I hear Shetland want their independence. This sounds like a joke, but it isn't. Shetland has a lot of oil and does not identify as part of Scotland. Shetland may demand to stay with the UK or go it alone (like the Faroes).