'All wood burns,' states Sir Bedevere. 'Therefore,' he concludes, 'all that burns is wood.' This is, of course, pure bullshit. Universal affirmatives can only be partially converted: all of Alma Cogan is dead, but only some of the class of dead people are Alma Cogan. 'Oh yes,' one would think. However, my wife does not understand this necessary limitation of the conversion of a proposition; consequently, she does not understand me, for how can a woman expect to appreciate a professor of logic, if the simplest cloth-eared syllogism causes her to flounder?
For example, given the premise, 'all fish live underwater' and 'all mackerel are fish', my wife will conclude, not that 'all mackerel live underwater', but that 'if she buys kippers it will not rain', or that 'trout live in trees', or even that 'I do not love her any more.' This she calls 'using her intuition'. I call it 'crap', and it gets me very irritated because it is not logical. 'There will be no supper tonight,' she will sometimes cry upon my return home. 'Why not?' I will ask. 'Because I have been screwing the milkman all day,' she will say, quite oblivious of the howling error she has made. 'But,' I will wearily point out, 'even given that the activities of screwing the milkman and getting supper are mutually exclusive, now that the screwing is over, surely then, supper may now, logically, be got.' 'You don't love me any more,' she will now often postulate. 'If you did, you would give me one now and again, so that I would not have to rely on that rancid Pakistani for my orgasms.' 'I will give you one after you have got me my supper,' I now usually scream, 'but not before'-- as you understand, making her bang contingent on the arrival of my supper. 'God, you turn me on when you're angry, you ancient brute!' she now mysteriously deduces, forcing her sweetly throbbing tongue down my throat. 'Fuck supper!' I now invariably conclude, throwing logic somewhat joyously to the four winds, and so we thrash about on our milk-stained floor, transported by animal passion, until we sink back, exhausted, onto the cartons of yogurt.
I'm afraid I seem to have strayed somewhat from my original brief. But in a nutshell: sex is more fun than logic. One cannot prove this, but it 'is' in the same sense that Mount Everest 'is', or that Alma Cogan 'isn't'.