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Article 2577 of comp.ai.philosophy:
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>From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Newsgroups: comp.ai.philosophy,sci.philosophy.tech
Subject: Re: Causes and Reasons
Message-ID: <5919@skye.ed.ac.uk>
Date: 8 Jan 92 22:49:05 GMT
References: <1991Dec24.014716.6901@husc3.harvard.edu> <1991Dec25.042628.18737@bronze.ucs.indiana.edu>
Reply-To: jeff@aiai.UUCP (Jeff Dalton)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 29

In article <1991Dec25.042628.18737@bronze.ucs.indiana.edu> chalmers@bronze.ucs.indiana.edu (David Chalmers) writes:
>>I repeat: what is implementation?
>
>There are many different ways in which one can define implementation,
>but they are all relevantly similar in kind.  Start with FSA's.  Take
>a simple FSA "program", e.g. "S1->S2, S2->S3, S3->S1" (I leave aside
>inputs and outputs for simplicity; they are treated in a similar
>fashion).  Then a physical system implements this FSA iff there is
>a partitioning of its states into 3 disjoint classes s1, s2, s3, such
>that its being in s1 causes it to go into s2, and so on.  (Other 
>restrictions may be added, but this part is the core.)
>
>The story for Turing machines is similar, though I won't spell out
>the details -- it simply involves ensuring a mapping from tape-states
>and possibly head-states to states of the physical system so that
>the state-transitions come out right.  The story for C programs is
>more complex still, but still similar in kind.  Each case involves
>a mapping from abstract states to physical states, and a requirement
>that the causal relations between the physical states satisfy certain
>conditions.  There's really nothing particularly difficult about this,
>so I don't see why you have such trouble with the notion.

There's a huge step from state transitions to C programs, since
a C program could be implemented by so many different patterns
of state-transitions.  Suppose we start from the causal relations
in a thinking entity, and take the corresponding program.  It
could the be reimplemented as a completely different pattern of
causal relations and yet, supposedly, this one would work just
as well for thinking.  I still don't see why that would be so.


