There are matters of principle and strategy at play in Nicola Sturgeon's approach to the question of the UK's membership of the European Union.

On principle, Ms Sturgeon is a pro-European and always has been and she will reiterate that in her speech in Brussels today. But as a strategist, she also believes (and has said it publically) that the in/out referendum could create the circumstances for another poll on Scottish independence by emphasising differences between Scotland and the rest of the UK.

On the principles, Ms Sturgeon is on solid ground. EU membership, she says, is vital for Scottish jobs and the economy and she is right to say so: leaving the European project would do tremendous damage to the domestic trade that Scotland and the rest of the UK does with the EU. This small nation also needs to attract migrants from across Europe who are eager to live and work here.

On questions of strategy, Ms Sturgeon is on much shakier ground. She says a second independence referendum would be unstoppable if a majority of Scots vote to remain in the EU but are forced to leave because of votes in the rest of the UK; she also calls for a so-called double majority which would prevent Britain leaving the EU unless there are separate majorities in favour in all four UK nations. However, constitutionally, this makes no sense. The UK is the EU member state (which Scotland voted to remain part of it) and it is the UK as a whole that will decide its future. What's more, the chances of it being invoked appear remote as poll north and south of the border suggest England and Scotland would both vote to stay in.

Where Ms Sturgoen is on much stronger ground is on how the case for staying in the EU should be put to the British people. In an interesting echo of the criticism she made of Better Together, Ms Sturgeon says David Cameron is being far too negative and should present a positive vision for staying in. If the UK Government wants us to remain in the EU, she says, it should give people something to vote for and there is some truth in what she says, although Mr Cameron is right to point to the places where this creaking organisation needs reform. It needs to be more accountable and democratic, it needs to be more responsive to its member states and it needs to cut bureaucracy and costs.

And we all know anyway why Mr Cameron is not yet ready to put the positive case. He has only just begun his charm offensive of an organisation in which he has done little to win friends and no one knows what material concessions, if any, he will win. He also has to be careful not to appear too enthusiastic about the EU at this early stage when he has just won an election with a tiny majority that could be swept away by Euro scepticism in his own party.

At some stage, though, Mr Cameron will have to break cover and put the positive case and, in time, it is likely to win the day, although no one, not even Ms Sturgeon, should take Scottish public opinion for granted - at the last European elections, one of the MEPs Scotland sent to Europe was from UKIP.

The British people also deserve the right to express their opinion on EU membership for the first time since 1975, when the organisation was very different, although it is interesting to hear Ms Sturgeon talk about the need for the referendum to settle the question of Europe for good. Something similar was said about last year's independence referendum, including by some in the SNP, but it is the question of the UK's membership of the EU that has the potential to perpetuate that other contentious question: Scotland's membership of the UK.