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From: simonpe@aisb.ed.ac.uk (Simon Perkins)
Subject: Re: Minsky's new article
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Organization: Dept of AI, University of Edinburgh, Scotland
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Date: Tue, 8 Nov 1994 15:35:04 GMT
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# It's an old argument, but for those who aren't familiar with it I'll
# give a brief example. I look at my screen right now, and there's a
# little yellow rectangle that represents the cursor. Now I know that
# yellow light has certain physical properties, and that it stimulates
# the visual receptors in my eyes in a certain way, and the receptors
# in turn send certain signals along the optic nerve to the visual
# cortex, etc.; but nowhere in that purely physical description of a
# sequence of events is there room for the *experience* of yellowness.

I think this is entirely circular. You are happy to accept that
looking at the yellow square on the screen causes a chain of
neurological events to occur in the brain, but then you deny that this
is the same as an `experience' of yellowness. In doing so you are
boldly saying that the experience of yellowness CANNOT be a physical
phenomenon. But this is what you are setting out to prove! Namely that
consciousness (and things `perceived' by it) CANNOT be a physical
phenomenon.

Here's an alternative argument based on the same situation (and
equally circular, but one that I happen to belive for other reasons -
see below):

From a mechanistic point of view (such as my own), the brain is a
(very complex) machine. Things like consciousness and intelligence are
dynamic `properties' or descriptions of the working machine.
Perceptual events such as the yellow square cited above trigger
changes in the working of this machine (I assume you have no problem
with this). And since `consciousness' is `merely' a description of the
machine, then the consciousness is also changed. Translating this
event into English, we say that we've experienced the yellow square.

I realise that the last paragraph contains some tough pills to swallow
for some people. After all we all `know' that we have the free will to
choose our behaviour, don't we? However, research in neurobiology in
animals has continually found that animal behaviour that at one level
is frequently explained in terms of `intentions' or 'desires', can
also be explained in terms of mechanistic neural ciruitry. My belief
(and unfortunately I have to use that word here) is that such
mechanistic explanations will ultimately describe all of human
behaviour (including such `non-mechanical' things as creativity). Note
that I don't believe we will ever be able to realistically predict how
a human will behave - the system is too chaotic and too complex for
that, but we will be able to see how the things that humans do can be
attributed to neural mechanisms. (As an analogy: in retrospect we can
see how weather changes are consistent with the laws of physics, even
if we can't use those same laws to predict the weather very far into
the future - and brains are almost infintely more complex).

For me, it is this (admittedly small, but growing rapidly) body of
neurological evidence, suggesting that behaviour is controlled by
mechanistic processes, that sets the mechanistic view apart from pure
`religion'. (But I'm prepared to admit - not that far...)

There are of course many other arguments against dualism but I think
I'll stop right there...

-- 
Simon Perkins                             simonpe@aisb.ed.ac.uk

Dept. of AI,
Edinburgh University.
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