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Article 2838 of comp.ai.philosophy:
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>From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Newsgroups: comp.ai.philosophy
Subject: Re: Searle, again
Message-ID: <6006@skye.ed.ac.uk>
Date: 17 Jan 92 19:14:37 GMT
References: <5907@skye.ed.ac.uk> <1992Jan08.230618.31038@spss.com> <5952@skye.ed.ac.uk> <1992Jan13.200632.36402@spss.com> <5984@skye.ed.ac.uk> <377@tdatirv.UUCP>
Reply-To: jeff@aiai.UUCP (Jeff Dalton)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 71

In article <377@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes:
>In article <5984@skye.ed.ac.uk> jeff@aiai.UUCP (Jeff Dalton) writes:
>|In article <1992Jan13.200632.36402@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>|>
>|>That's not the same thing.  What allows the brain to support understanding
>|>might conceivably be its information-handling capabilities-- that is, 
>|>something that can be duplicated rather than simulated on a computer.
>|
>|But Searle thinks he has shown it isn't that.  It's _something else_
>|about the brain.  The something else that matters is the causal powers.
>
>Yes, and *this* is the point of disagreement.  I have yet to see any
>compelling evidence that any such 'something else' even exists.

Ok.  Searle doesn't argue "brains have causal powers and computers
don't, so therefore ...".  The "causal powers" arrive as a conclusion,
if anything, and not a premise, in the argument against Strong AI.

Searle says "brains cause minds".  He then shows that merely
implementing a program isn't enough to cause a mind.  So it must
be the "causal powers" of brains, and not any programs they happen to
be implementing, that enable them to do the trick.  But the "causal
powers" are not something he uses to show implementing the a program
isn't enough to cause a mind.

Indeed, so far as argument about AI are concerned, Searle could
get by without mentioning the causal powers at all.  They come in
only when he says that he doesn't think there's necessarily anything
special about brains.  Anything with equivalent causal powers would
do.  He gives the example of martians and "green slime".

For the details, for why he says "brains cause minds", and so on,
read his first Reith Lecture, ie, Chapter 1 of _Minds, Brains and
Science_.

>Why should I assume that this 'something else' exists?
>What line of reasoning does he follow in concluding that it exists?

Why not read and find out?

>What axioms or assumptions does he make in arriving at this conclusion?

The demand for axioms is a bit excessive, don't you think?  It's
not like we're proving theorems in geometry.

>Now, how does he reach the conclusion that these
>'causal powers' even exist?

If you are willing to allow that humans do have minds, then there
are various ways this might come about.  For instance, there could
be some spiritual substance, in addition to the material substance
of the brain, that causes them.  For various reasons, Searle doesn't
want to take that route.  Instead, he argues that we should see
brains as causing minds and minds as being realized in brains.

But again, for the details, see the first Reith Lecture.

>I think the main reason people tend to see these 'causal powers' as an
>assumption is that they (we) cannot see how he gets to them.  And so,
>since they seem (perhaps superficially) to be unsupported by evidence,
>we tend to jump to the conclusion that thier existance is an axiom to
>Searle.

That seems a reasonable conclusion to me.  However, if you read
_Minds, Brains and Science_, I don't think it will seem that he just
pulls them out of the air or takes them as an axiom.  I don't know
whether Searle's Asi Am article or the article reprinted in _The
Mind's I_ would also expalin this.  Indeed, I don't even remember
whether they mwention "causal powers".

-- jd


