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Article 2345 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?
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Date: 21 Dec 91 05:08:17 GMT
References: <40822@dime.cs.umass.edu> <1991Dec18.193242.10535@bronze.ucs.indiana.edu> <BSIMON.91Dec19071828@elvis.stsci.edu> <1991Dec21.015200.14397@bronze.ucs.indiana.edu>
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Bernie Simon writes:

>>This argument ignores the fact that neurons have chemical as well as
>>electrical behaviour. Since no "Chinese room" can secrete or absorb
>>chemicals, any such replacement for a neuron could not be functionally
>>identical for the cell it replaces.

David Chalmers replies:

>We simulate the chemical behaviour too.  No difference in principle.

This is an adequate answer unless Bernie Simon means to focus on
the chemical interface between the silicon neurons and the biological
tissue with which it communicates in some fashion.  Here simulation
will not suffice.  This is especially an issue in David Chalmers' 
version of the thought experiment where the neurons are replaced 
one at a time.  
	One could imagine tiny chemical reservoirs with computer-
controlled release mechanisms (not unlike fuel injection control
in automobiles), which would enable a silicon neuron to release
an appropriate amount of e.g. acetlycholine at just the right times.
Such chemical release would be needed only at the interface between
silicon and biological tissue; the silicon/silicon interface could
be simulated as Chalmers suggests.
	Searle's objection that "formal symbols have no causal 
power" has much less force to me in this imagined situation, as 
the program running on the silicon neuron is causing the release 
of neurotransmitters.


