Re: Logic

From: Philip Jonkers (
Date: Thu Jul 26 2001 - 11:13:36 BST

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    Subject: Re: Logic
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    Quoting TJ Olney <>:

    > Perhaps the difficulty is that there are many kinds of logic.
    > The following represents one that Bateson labeled (for reasons
    > I'd enjoy knowing), logic in Barbara.
    > Men die.
    > Grass dies.
    > Men are grass.
    > It is just as "logical" as the more common syllogistic form,
    > but represents a different "kind" of logic.
    > All men die.
    > Socrates is a man.
    > Socrates must die.

    I would say the former is not logic at all, the latter,
    of course, is.
    Let's look at the first exhibition of `logic'. The first
    premises are perfectly rational, but the conclusion is irrational.
    Look at it symbolically:

    We have the following perfectly logical premises:
    1. Men -> die
    2. Grass -> die
    3. die NOT-> grass (:`death' does not lead to `grass')

    The conclusion:
    Men -> grass

    is valid iff
    Men -> die -> grass

    which is in contradiction with premise 3. Therefore `logic in
    Barbara' is no logic at all. Well, at least your statement of
    it. Please TJ don't smear such a nice name with pretentious
    intent (my sister has the same name!).

    The second one is trivially sound:

    ALL elements of the set of men -> die
    Socrates is an element of the set of men ->
    Socrates -> dies

    So having invalidated your first suggestion of logic, do you
    have more in store for me? I'm a firm believer in a single
    kind of logic (a real one, anyway). Wouldn't we have multiple
    kinds of mathematics, if we had more versions of logic?


    Philip Jonkers.

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