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Article 2221 of comp.ai.philosophy:
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>From: mclarke@daisy.ee.und.ac.za (Matthew Clarke)
Subject: Re: Scaled up slug brains
Message-ID: <1991Dec18.071959.4921@daisy.ee.und.ac.za>
Organization: Univ. Natal, Durban, S. Africa
References: <12689@pitt.UUCP> <40650@dime.cs.umass.edu> <12708@pitt.UUCP> <44970@mimsy.umd.edu>
Date: Wed, 18 Dec 1991 07:19:59 GMT


In <12708@pitt.UUCP> geb@dsl.pitt.edu (gordon e. banks) writes:

>Put it this way.  We understand the way system X(1) works.  System X(2)
>is a little bit more complex than X(1).  It is a good bet that it
>works the same way, but is just more complex.  X(3) is a bit more
>complex than X(2).  And so on until we get to humans X(n).  There
>isn't really any place where you can draw the line since as you
>look at different organisms, there seems to be a pretty smooth progression
>in complexity.  The place most people who draw lines draw it is between
>say, the chimp and man, but there are obvious problems there too.
>You want to draw it between the worm and man because there is so
>much difference there it is easy to convince yourself that the same
>principles aren't involved.  But if you draw it there, you have
>the problem of deciding at which phase of evolution this *radical*
>difference in the way nervous systems operate occurred, and why.
>Care to take a crack at this?

I'll take a crack at it on behalf of Donald MacKay, one of Britain's
foremost reasearchers in neuroscience until his death in 1987. Mackay
points out that the call to "draw a line" is misguided.

Consider a man immediately after
he has shaved his face and consider another man with a well-grown beard.
Where does one draw the line between having a beard and being clean shaven?
One could make a continuos set of measurements between the one and the other,
yet there is a qualititave difference between the two. There is nowhere one
can "draw the line" and yet it is quite sensible to talk of some people having
beards and some being clean shaven.

Likewise, I see no problem (*) accepting that there is a continuum of brain
complexity from lower to higher animals, while still maintaining that humans
have minds while sea-slugs do not. There is no point in trying to draw
a quantitative line when the difference is qualitative. 

(*) By "no problem" I mean no philosophical problem, there is of course the
empirical problem that brain complexity of various animals does NOT form a
continuum, but a discrete series with some (rather large) holes.

                         Matt.          



