The second, and minor point – which I now regret raising as it is threatening to muddy the water with a lot of unnecessary technicalities – was that his interpretation of metaphorically “chucking a thing in a skip” did not even correspond to the standard procedure of logical negation. If this phrase was to have a simple, clear-cut logical meaning – Norm’s assumption not mine – then surely it should be that, should it not? But I make no claims that it should have such a straightforward interpretation. In fact it obviously does not.

So, if we are to discuss the applicability or otherwise of De Morgan’s laws to political disputes, then I look forward to it. But I request that you don’t misrepresent my position. In particular, it is inaccurate to suggest that I am trying to inflict some nightmarish formalistic ‘enterprise’ on everyone, with Norm playing the role of the heroic resistance and defender of commonsense.

That may be how he is trying to frame the debate, but in fact the contrary is true. If I am to be taken to task for applying broad, abstract principles of logic to a political dispute, then it seems fair that he should recieve the same treatment (with perhaps added force), since it was he who first introduced them into the discussion!

I just pointed out that he did so rather ineptly.

I am questioning your entire enterprise, especially since De Morgan’s laws are not even the only possible rules (ie, the axioms on which they are based give rise to different rules if different axioms are chosen). In other words, there are many formal logics, not just one, so even without any experience of the world, a reasonable person would question your application of this one logic to human reasoning. This subject is too long for a comment, so I’ll respond with another post in a few days.

I plead not guilty! I’m well aware that formal symbolic logic is of limited value in most human discourse. In most practical arguments, such universal, general, timeless, logical techniques do not produce anything which isn’t fairly obvious anyway. (Our subconsiouses seem to be ahead of the game on that score.)

That isn’t to say that such rules are not valid, though. Framing a question suitably and identifying its precise assumptions and conclusions can lift it from its local situation into the timeless (in my view, anyway). Usually though, this framing is enough on its own to make the conclusion fairly obvious. The law of deduction, or whatever, is not then especially useful as an analytical tool – I’m not claiming otherwise.

When all goes smoothly, such general logical architecture goes largley unnoticed, as it should. My point – misrepresented in the post you link to – is that if you do try to exploit it to force through conclusions which are to any extent non-obvious, it is quite possible to make a mess of it, and this may be simply your mistake, rather than illustrative of the unsuitability of the tools, as Norm demonstrated.

Of course, the way that theory has developed doesn’t make it necessarily any better a foundation for decision making than the usual model though, so far as I am aware, nobody has looked at whether it is or is not.

Seemed a bit incongruous that the next piece on the news was about how Obama has to reach a decision about whether to deploy more troops to Afghanistan. But then again, I guess it is a measure of the ness Bush/Cheney left us in.