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Jordan DeLong scripsit: > Why do we want to use an outdated logic? We already have features > of modern logic which Aristotle didn't have (bu'a, lambda stuff, > whatnot). Should we give those up too? Every bit of Aristotle's logic is consistent and compelling by modern standards, once you get past the broken "some S is not P" reading for O. Aristotle's original and correct reading "not every S is P" has the correct non-import semantics. We should not give anything up, *including* Aristotelian logic. > Aristotle used XOR for "or" also---I don't see you saying we should > be doing that. We have both or and xor. What's the issue? > Yes, but those things are useless. Modern logicians have a much > simpler "square", and it hasn't hurt them any. They are not "useless". They support widely accepted varieties of common-sense reasoning. > But we don't want to have to write that. I want to be able to say things > like > ro pavyseljirna cu blabi > and have it be exactly the same as > ro da zo'u ga da na pavyseljina gi da blabi > and > ro da poi pavyseljirna zo'u da blabi And so? You do, but I do not. I want "ro pavyseljirna cu blabi" to count as false, not true, and ditto with "ro pavyseljirna cu zirpu". At the common-sense level, there *aren't* any unicorns, white, purple or otherwise. (I am not here talking about possible or fictional worlds in which there are unicorns -- substitute "even primes > 2" if you like.) > Yeah, that case is nonimportant---I didn't know back when we were > discussing this last. But in a system of modern logic, it can be > proven as a theorem that the universe is nonempty (or at least it > can in Quine's). And it can also be shown intuitivly: we have a > set of all things, which is a thing, and a set of nothings, which > is another thing---so we can't have an empty universe. If sets count as things, then the "set of all things" will not work: see Cantor's paradox, which shows that the notion "set of all sets" is ill-formed. -- And through this revolting graveyard of the universe the muffled, maddening beating of drums, and thin, monotonous whine of blasphemous flutes from inconceivable, unlighted chambers beyond Time; the detestable pounding and piping whereunto dance slowly, awkwardly, and absurdly the gigantic tenebrous ultimate gods -- the blind, voiceless, mindless gargoyles whose soul is Nyarlathotep. (Lovecraft) John Cowan|jcowan@hidden.email|ccil.org/~cowan