From: crawford@boole.mitre.org (Randy Crawford)
Subject: Re: Atheism and Intelligence
Organization: The MITRE Corporation, McLean, VA
Date: Fri, 18 Dec 1992 06:24:38 GMT

In article <1992Dec16.231131.1173@umr.edu> S106495@UMRVMA.umr.edu writes:
>I never implied that gut instinct was a replacement for rational
>thought.  I meant that if we define one system of "logic" as best, we
>exclude improvement s in our methods of thinking.  I believe quantum
>physics obeys some logic      similar to our own, but we must redefine
>our perspectives on it to understand.   

>Another alternate logic I am
>speaking of is neural networks.  These are        computer algortithms
>where the machine takes the factors toward a given         conclusion,
>and thru trial and error perfects an algorithm to give a conclusion.

Not `a' conclusion.  NNs can only lead you to `the' predetermined conclusion.
NNs are useful only when you know the goal state, but don't know how to
get there.

In no way do NNs resemble _any_ form of logic equivalent.  Trial and error is 
not a form of reasoning -- it couldn't be.  In logic, you don't yet know the 
conclusion you need to reach.  You have confidence that in the use of the 
method (which you understand and can verify) and that you will reach a 
reproducible and valid conclusion.  In trial and error, you know the conclusion
but not how to get there.  How then could you use trial and error to reach a 
logic-like conclusion when you can't tell at each step whether you have made 
any forward progress since you don't know what the conclusion is nor if you're
approaching it?

>For example, it would take an list of approved insurance applications,
>and rewite its formula to match the applications that were accepted
>so that in the  future it could decide to accept the application.

Yes.

>The point is all forms of thought must be evaluated on their
>merits and   from time to time our thought processes should change.  I
>cannot use gut         instinct to write a computer program any more
>than I can use logic to write a  joke.  

Not true at all.  You can certainly use logic to write a joke, as long as you
understand the method of writing or telling jokes.  The method (or logic) is
simply a skill which leads you from your start state to your goal state via a
reproducible sequence of operations based on an understanding of the process
of writing funny jokes.

It is possible that following a method will not necessarily lead you to a funny
joke every time.  If the process of being funny is not fully understood (or
reproducible deterministically) then the results of applying it will not always
succeed. Such an incomplete process in the hands of a master is considered art.
If the process _is_ reproducible, it is a mathematical science and it _will_ 
produce funny jokes every time.

Logic is, by that definition, a mathematical science.  Trial and error is not.
The two can never be equivalent.

>Some balance must be struck
>between the two for many tasks, especially   creativity and problem
>solving.  There is no algorithm to come up with new ideas, but you can't
>just "use the force" to get them either.  Neural networks will probably
>be able to solve some problems using neither gut instinct nor syllogisms.  

I don't think NNs have ever solved _any_ problems.  Nor will they ever.  Like
genetic algorithms, they are simply a tool for finding your way blindly from 
a place you know to another place you know, via a path you don't know, and 
only when you can determine whether each step takes you nearer or farther 
from your destination.  You use them to search for something, not tell you 
what you are searching for.

This is not to condemn neural nets or genetic algorithms in any way.  However
they can never take the place of logic nor even supplement it.  They are not
reasoning methods; they are search methods.  Logic is a reasoning method -- 
the only one in which I have any experience or confidence.
-- 

| Randy Crawford        crawford@mitre.org        The MITRE Corporation
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