From: Lee Corbin (lcorbin@tsoft.com)
Date: Tue May 14 2002 - 22:43:19 MDT
Now whenever one begins to discuss logic, one should attend to the
possible confusions over the term. Here, I use
formal logic: axioms, derivations, and theorems (purely mathematical)
informal logic: conditionals, converses, etc., premises, assumptions,.
everyday logic: using good judgment in selecting which facts to
pay attention to, and which to virtually ignore.
Let me know if these categories bug you, or if you think that something
else is more standard.
Formal logic, of course, has utterly no use in daily life. Even
puzzles such as Carroll's famous
1. Babies are illogical;
2. No one is despised who can manage a crocodile;
3. Illogical persons are despised.
don't require more than informal logic for their solution (though
I find expressing those with the expressions of formal logic to
often be helpful). See below for solution.
But IMO problems of this difficulty just *never* come up in daily life.
When we accuse someone of being illogical, I think that it means that
the person is deliberately ignoring some facts which are perfectly well
known to him or her, but which he or she thinks to be of no importance.
At least, when I try to recall someone who seems to be acting or
speaking illogically, it seems to boil down to poor judgment on
his or her part, nothing more. Even children, I submit, can rarely
be found to be making an outright mistake in informal logic.
The reason for this is that all our reasoning about the world is
informed by a vast number of facts, only some of which are we
consciously aware of. So syllogism is practically never relevant,
and rarely used. (This is another reason that hard-AI has so
far failed.)
Consider this illustration: Q. When did the first human being
employ something like informal logic? A. At 7pm on October 23
in the year 179,206 B.C. on the east shore of the Arabian Sea.
Viz., a minor chieftain was simultaneously conscious of three
facts: 1. the Sacred Knife ceremony required the Sacred Knife;
2. Kunsenti Fut was in possession of the Sacred Knife; 3.
Kunsenti Fut's tribe had come to the ceremony, but no one
had brought Kunsenti Fut!
At first, this disturbed the chieftain only slightly; in the
course of his life, every day he often felt ill at ease when
things didn't seem to be going right. But they were never
black and white. If something was missing, something else
would have to do, that's all.
This was different: the more he thought about it, the more
ironclad the discomfort was. Finally the words rolled around
in his brain and settled into:
1. Ceremony cannot take place without Sacred Knife
2. Sacred Knife is with Kunsenti Fut
3. Kunsenti Fut is not at scene of Ceremony
"***THEREFORE*** (historical first) IT IS INESCAPABLE: Ceremony
cannot take place!"
Okay, so I agree with Edward Gibbon who wrote "Education is
seldom of much efficacy except in those happy dispositions in
which it is almost superfluous". True, Gibbon was talking about
moral education (Decline and Fall, vol. 1). But I think that
it applies to teaching logic to people in general. In other
words, people who seem illogical to you aren't: they only
have bad taste about what they consider relevant in the huge
matrices of information on which, in almost every situation,
our judgment depends.
Lee
P.S. The answer to the Lewis Carroll puzzle: From 1 and 3,
we have "babies are despised", and since "no one is despised
who can manage a crocodile", it follows that babies cannot
manage crocodiles. See his "Symbolic Logic" for much harder
ones.
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