The acrimonious tone now developing is worrying and deplorable. Whatever the result of the referendum, we all have to live together afterwards. Likewise we have to live, one hopes in friendship and concord, with our English neighbours, whether we remain part of the same state or not. Bitterness now will not be forgotten quickly, harmony difficult to restore. This is why sensible people, looking ahead, hope that the outcome is clear-cut, with a substantial majority for the winning side. A 51-49 result either way would be profoundly unsatisfying. Negotiating the last weeks of the campaign is going to be a test of character.

Having insisted that the right to vote in the referendum should be restricted to those on the Scottish electoral role, Alex Salmond is now seeking to present it as a contest between the Scottish and UK governments. Hence his demand that David Cameron should debate with him. Cameron has refused to do so, insisting that the question is for Scots to decide. This is not, I assume, because he fears he might lose such a debate, but because, in the Edinburgh Agreement, he accepted Salmond's terms, and is determined that the Scottish First Minister should not be granted the opportunity to present himself as the defender of Scottish interests against an English prime minister. So any debate should be between Alex Salmond and Alistair Darling.

Thus far most of the argument has been about detail, and certainly there are people who say they want more clarification about matters such as the currency, arrangements for taxation, social security and pensions, EU membership, defence, the future of North Sea oil and gas, energy policies, etc, before they make up their mind.  There are doubtless many whose votes will be determined by such matters, but I suspect they are in quite a small minority. Most voters will no more read the small print than they read party manifestos at a general election.

David Hume, the greatest of Scottish philosophers — perhaps the greatest of British ones — lived in what is still often called the Age of Reason. Nevertheless he wrote: "We speak not strictly and philosophically when we talk of the combat of passion and of reason. Reason is, and ought only to be, the slave of the passions, and can never pretend to any other office than to serve and obey them." By the "passions" he meant what we might rather call "sentiments" or "feelings", and it is certainly these, rather than the exercise of reason, which will usually determine people's political opinions. I have no doubt that in most instances, it will be the passions — sentiments and feelings —which will lead people to vote Yes or No. They will vote Yes if they feel themselves to be Scottish and not British; No if they are happy in a dual identity; Yes if the thought of change pleases them; No if it doesn't. And in both cases they will leave the detail to take care of itself.

At present, despite that recent wobble, the Better Together campaign remains in the lead, albeit by a narrowing margin. The danger for it is not that the nationalists will suddenly pull attractive rabbits from a conjurer's hat, but that, in the last weeks of the campaign, they will make a stirring appeal to Scottish national sentiment, one to which many now wavering or lukewarm may respond. But the unionists also have historic sentiments to appeal to, and sentiments of cross-border family connections and friendship too, feelings not lightly to be discarded. Sentiment is powerful and the unionists have a particular appeal to two groups: women voters, who are perhaps more conscious than men of these bonds of family and friendship, while also more sceptical of politicians' promises and of the benefits of political change; and the young belonging to what has been called the Facebook generation, whose outlook is global rather than national or parochial. Interestingly, mock-referendums in schools and universities have produced substantial majorities in favour of a No vote. This suggests that if the nationalists don't win in September, they may never do so.