A novice poker player quickly learns - or had better quickly learn - that strength often connotes weakness and weakness is a reliable indicator of strength. But as the stakes increase and the level of play becomes more sophisticated such elementary tells can be misleading. They are false friends in the land of the double and triple bluff.
So a novice poker player might conclude that David Cameron's refusal to debate against Alex Salmond is a sign of weakness. A slightly more experienced player would think this weakness too obvious to be true and conclude that Cameron is holding better cards than he is indicating. And it is true: with the polls indicating a No vote Cameron has little need to risk a debate the outcome of which must be uncertain. He is, if you like, the chip leader and need only play occasionally and when he thinks he's on a sure thing.
But a still more experienced player might look at Cameron's prior history in debating (not so good!) and use that information to conclude that Cameron really is holding weak cards. Press him and he will fold. As, in fact, he has.
Of course it is also an iron law of politics that the party or candidate asking for a debate is the party or candidate in a hole. Otherwise, why risk this kind of encounter?
It is true that Salmond believes he'd run rings around Cameron. He should. After all, this is the argument he's been having since he was a student at St Andrews University. Cameron, by contrast, is a novice in these matters. Which, doubtless, also explains why Cameron is disinclined to take part. What's in it for him?
There is ego here too. Salmond does not wish to debate Alistair Darling - the head of the Better Together campaign - because doing so is beneath him. Why should Salmond - First Minister of Scotland - be expected to debate a mere opposition backbencher? The very notion is contemptible!
So, as Salmond says, Cameron is feart. Perhaps he is. But there is logic to Cameron's retreat that rests upon something greater than his chances in a one-on-one dust-up with Il Tartanissimo. As the Prime Minister put it:
"You want the independence debate to be an argument between you and me; the Scottish Government and UK Government; the SNP and Conservative Party - in fact anything rather than what it really is about. Nor is your argument with the rest of the United Kingdom, it is with the people in Scotland."
This is true and it is part of the nationalist strategy to a) elevate Salmond's position and b) make it seem as though the Prime Minister of the United Kingdom is a foreigner in his own country. Which is a cute trick to pull off. It's also the case that Salmond has repeatedly criticised Cameron for interfering in Scottish politics. This time, however, he'd like a little more interference because he counts on Scottish Labour voters deserting the Union rather than ally themselves with David Cameron and his merry band of grouse-shooting, bedroom-taxing Tories. (It is no secret, I think, that Darling is worried this really could happen. It seems likely he has suggested Cameron keep a low profile.)
Comparisons with the Canadian precedent do not quite work. Pierre Trudeau (1980) and Jean Chretien (1995) both debated in Quebec's independence referendums but, of course, they were both Quebeckers making the case for the Canadian federation. If Gordon Brown were still PM I'd fancy he'd have been content to debate Salmond. Anyway, neither Trudeau nor Chretien could credibly be lampooned as some kind of alien bastard lacking standing of any sort. Cameron can. And is.
And yet, there is still something feeble about all this. In the first place Cameron has been bullied off the pitch. Discretion may be the better part of valour and all that jazz but it's still mildly ignoble and unsatisfactory.
The Prime Minister of the United Kingdom has, effectively, been barred from one part of the United Kingdom and he seems content to accept this. In all the small or tactical details, logic and prudence may be on Cameron's side but, viewed from a broader perspective, there is still something humiliating about this. And if the Prime Minster of the United Kingdom will not make the case for the United Kingdom then who the hell will?