IS there a moral argument for keeping an independent Scotland out of the EU?

Joseph Weiler thinks so.

The academic - president, no less, of the European University Institute in Florence - believes that nationalism runs so counter to the spirit of European integration that a Yes vote should be punished by years in the wilderness.

He's not alone. Some of the continent's most ardent federalists, those at the heart of the European project, are really struggling to get their heads around why so many Scots want to dump one union, Britain's, while keeping another, Europe's. Worse for the SNP and its allies, the thing they hate most about what they would see as separatism is that their beloved European project has helped to spawn it, by prompting the mantra of "independence in Europe".

"The EU should not seem like a Nirvana for that form of irredentist Euro-tribalism which contradicts the deep values and needs of the Union," the South African-born Weiler declared in perhaps the most eloquent expression of the view. "The assumption of automatic membership in the Union should be decisively squelched by the countries from whom secession is threatened." And if said member states baulk at such threats, he said, then others should do so for them, with "France in the lead".

This view - let's call it the Weiler Doctrine - goes some way to explain that quiet chill in Brussels towards nationalism in Scotland and, especially, Catalonia. Pro-independence parties in both countries hope their Europhile credentials - in the SNP's case, far superior to the UK's ruling Tories - will win them friends. And they do. But only up to a point.

"It would be hugely ironic if the prospect of membership in the Union ended up providing an incentive for an ethos of political disintegration," Weiler has written on Catalonia, suggesting that leaving Spain would be a "betrayal" of the European ideal.

This, of course, makes nationalists smart, not least because the premise of the Weiler Doctrine is that states like Spain or Britain represent a pluri-national togetherness that, in the spirit of the EU, combines unity with diversity. But do they? Certainly, in the UK, there are some unionists, such as Labour's Gordon Brown, who talk of a British "family of nations" - a phrase once dutifully repeated by Soviet propagandists as they re-imagined the old Russian empire.

But there is another side to British unionism that is far less accommodating to the idea that the UK is a multi-national state and Scotland, therefore, a stateless nation. These ultra-unionists prefer to think of the still very centralised UK as a nation-state in its own right; a country, not a mini-EU.

Many of those who see the British as a single people want to leave the EU. Is this nationalism morally superior to Scottish variety? Of course not. The question, therefore, for Weiler and his federalist friends, is which nationalism poses the biggest threat to the EU ideal? The national chauvinism of populist parties like Britain's Ukip and France's Front National? Or the euro-enthusiasm of separatists in Scotland and Catalonia?