From newshub.ccs.yorku.ca!torn!utcsri!rpi!usc!sol.ctr.columbia.edu!usenet.ucs.indiana.edu!bronze.ucs.indiana.edu!chalmers Wed Sep 16 21:23:28 EDT 1992
Article 6913 of comp.ai.philosophy:
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>From: chalmers@bronze.ucs.indiana.edu (David Chalmers)
Subject: Re: Consciousness
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Date: Mon, 14 Sep 1992 23:27:40 GMT
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In article <1992Sep12.054041.20257@muug.mb.ca> kenwolfe@muug.mb.ca (Ken Wolfe) writes:

>I've been following this thread and there is something I am wondering
>about your discussion of replacing sections of the brain with
>"prosthetics".  You seem to suggest that if this is done all at one time
>consciousness would be radically changed, but if it were done gradually,
>or rather one small part at a time, consciousness would be unaffected. 
>Would the end result of bothe of these hypothetical operations not be
>exactly the same?  I am not clear on how the speed of these prosthetic
>replacements, or their granularity if you prefer, would affect the final
>state of consciousness.  

I'm not arguing that a given endpoint will differ in its states of
consciousness according to how quickly one makes the replacement.
It seems very unlikely that consciousness is dependent on history
in that sort of way.  What I'm saying is that the different styles
of replacement will in fact lead to different classes of endpoints.

Style A (Change chunks of arbitrary size):  By this method,
one could get from a brain to a giant lookup-table, which is
hypothetically behaviourally equivalent, in a single step.

Style B: (Change small chunks at a time): The ensures that at all
stages, the systems will be equivalent in functional organization
to some considerable level of detail.  There will be no way to get
from a brain to a lookup-table by replacing small chunks one by
one with I/O equivalent chunks.

It's true that for any endpoint that is reachable by Style B, one
could instead perform a quick Style A replacement that will give
you the same endpoint, but the reverse doesn't hold, as seen with
the example of the lookup-table.  It seems to me that Style B
replacements will always leave conscious states invariant, but
that Style A replacements need not do so.  Of course, the class
of Style A replacements that don't leave consciousness invariant
will be contained in the class of Style A replacements that can't
be achieved by Style B.

-- 
Dave Chalmers                            (dave@cogsci.indiana.edu)      
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."


