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Article 2252 of comp.ai.philosophy:
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>From: orourke@unix1.cs.umass.edu (Joseph O'Rourke)
Newsgroups: comp.ai.philosophy
Subject: Re: Searle's response to silicon brain?
Message-ID: <40852@dime.cs.umass.edu>
Date: 18 Dec 91 19:21:57 GMT
References: <40822@dime.cs.umass.edu> <1991Dec18.172040.3506@spss.com>
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Reply-To: orourke@sophia.smith.edu (Joseph O'Rourke)
Organization: Smith College, Northampton, MA, US
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In article <1991Dec18.172040.3506@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>In article <40822@dime.cs.umass.edu> orourke@sophia.smith.edu (Joseph O'Rourke) writes:
>>Can anyone tell me if Searle has reacted to the counter-
>>Gedanken experiment of replacing each neuron in a brain
>>with a silicon, digital, neuron simulator?  [...]
>
>"One can imagine a computer simulation of the action of peptides in the
>hypothalamus that is accurate down to the last synapse.  But equally one
>can imagine a computer simulation of the oxidation of hydrocarbons in a car
>engine....  And the simulation is no more the real thing in the case of the
>brain than it is in the case of the car...."
>--Searle, Scientific American Jan. 1990, p. 29.
>
>Searle believes that understanding and other mental phenomena have some
>*physical* basis, tied to their actual implementation in the brain, which
>computers cannot reproduce, although they could simulate them.

Thanks for providing that quote.  Although it does seem to imply
which position Searle would take on a silicon brain, I am still
uncertain, because I see some differences between his discussion of
the limitations of simulation, and what I am suggesting.
	First, an off-line simulation of digestion seems different
from an in-situ replacement of neurons.  One can imagine the silicon
neurons interfacing with the remainder of the body (muscles etc.)
through clever mechanical devices that release the appropriate
chemicals at just the right times.  Thus although there is no
question that this is not "the real thing," it does have real
effect, causal power: they cause the muscles to contract and the 
person to speak.
	Second, Searle says "It seems obvious that a simulation of
cognition will ... not produce the effects of the neurobiology
of cognition."  But I am not simulating cognition:  I am simulating
individual neurons, which are interfaced so that all external
observables are unchanged.  The pattern of silicon neuron "firings"
are to be identical to the pattern of real neuron firings; the
signals sent to the muscles are to be the same.
	Third, I recall that Searle said someplace that if the
neurotransmitters in the brain were all replaced by swift demons
that had the same functional effect, the person *would* still
understand.  If so, then he does countenance a partial replacement
of the biological apparatus of the brain without loss of the
magical understanding.  I am wondering where he draws the line.


