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From: sher@rochester.UUCP
Newsgroups: comp.ai,comp.misc
Subject: Re: Learing about AI
Message-ID: <24783@rochester.ARPA>
Date: Fri, 13-Feb-87 09:17:24 EST
Article-I.D.: rocheste.24783
Posted: Fri Feb 13 09:17:24 1987
Date-Received: Sat, 14-Feb-87 14:54:52 EST
References: <375@atux01.UUCP> <12992@sun.uucp> <278@vax1.ccs.cornell.edu>
Reply-To: sher@rochester.UUCP (David Sher)
Distribution: na
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 47
Keywords: Logic AI
Xref: utgpu comp.ai:231 comp.misc:226
Summary: Logic is a language.

If I didn't respond to this I'd have to work on my thesis so here
goes:
I think there seems to be something of a misconception regarding the
place of logic wrt AI and computer science in general.  To start with
I will declare this:
Logic is a language for expressing mathematical constructs.

It is not a science and as far as artificial intelligence is concerned
the mathematics of logic are not very relevant.  Its main feature
is that it can be used for precise expression.  

So why use logic rather than a more familiar language, like english.
One can be precise in english, writers like Edgar Allen Poe, Issac 
Asimov, and George Gamov all have written very precise english on a
variety of topics.  However the problem is that few of us knowledge
engineers have the talent to be precise in our everyday language.
There are few great, or even very good writers among AI practitioners.

Thus for decades engineers, scientists, and statisticians have used
logic to express their ideas since even an incompetent speaker can be
clear and precise using logical formalisms.  However like any language
with expressive power one can be totally incomprehensible using logic.
I have seen logical expressions that even the author did not
understand.  Thus logic is not a panacea, it is merely a tool.  But it
is a very useful and important tool (you can chop down trees with a 
boy scout knife but I'll take an axe any day and a chain saw is even
better).  Also like english or any other language the more logic you
know the more clearly and compactly you can state your ideas (if you
can avoid the temptation to use false erudition and use your document
to demonstrate your formal facility rather than what you are trying to
say).  Thus if you know modal or second order logics you can express
more than you can with simple 1st order predicate calculus and you can
express it better.  

Of course, not everyones goals are to express themselves clearly.
Some people's business is to confuse and obfuscate.  While logic can
be put to this purpose it is easier to use english for this task.   It
takes an uncommon level of expertise to be really confusing without
appearing incompetant with logic.

Note: I am not a logician but I use a lot of logic in my everyday
work which is probabilistic analysis of computer vision problems
(anyone got a job?).
-- 
-David Sher
sher@rochester
{allegra,seismo}!rochester!sher