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From: torkel@sics.se (Torkel Franzen)
Newsgroups: comp.ai.philosophy
Subject: Re: Minds, machines, and Godel
Message-ID: <1991Jan18.203249.7022@sics.se>
Date: 18 Jan 91 20:32:49 GMT
References: <1991Jan16.182120.20961@sics.se>
	<1991Jan18.012527.20104@news.cs.indiana.edu>
	<1991Jan18.083759.19131@sics.se>
	<1991Jan18.191303.6840@bronze.ucs.indiana.edu>
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In-Reply-To: chalmers@bronze.ucs.indiana.edu's message of 18 Jan 91 19:13:03 GMT


In article <1991Jan18.191303.6840@bronze.ucs.indiana.edu> chalmers@bronze.ucs.
indiana.edu (David Chalmers) writes:

>Now, I don't know in practice whether we can know whether a
>given TM is an accurate simulation of us or not, but it doesn't seem an
>unreasonable claim, with the wonders of cognitive science and neurophysiology.
>Importantly, to use this as your refutation of the argument, it is you who
>have to make the strong claim (a la Benacerraf) that we necessarily cannot
>discover the TM that we are (or more precisely, a TM that accurately
>simulates us).  I don't see any independently-supported reason for such a
>claim, although it's certainly a logical possibility.

  I claim nothing concerning what we can or cannot necessarily discover.
To refute your argument I need merely show that it is inconclusive. You
still have said nothing to substantiate the claim that if ZFC+UM codifies
the humanly provable arithmetical statements, we must be able to convince
ourselves of this. Vague (or rather vacuous) appeals to "the wonders of
cognitive science" carry no more weight than a bald claim that humans
can establish the truth of any true arithmetical statement.

  >Well, the form of the argument is a reductio.  If you did this, and you
  >provided convincing evidence for this claim, and I had good reason to
  >believe that I was consistent (the role of the last two assumptions has been
  >gone over in this and the previous posts), then I could then assert the
  >statement "ZFC+UM is consistent", and its arithmetical analog (or
  >alternatively, I could assert the Godel sentence of the theory).  I would
  >thus have asserted a statement outside the bounds of the theory.  
  >Contradiction.

  These remarks are nothing to the point. Obviously I am not claiming to
have convincing evidence that ZFC+UM codifies the humanly provable
arithmetical statements. I have been told, let us say, by God in a dream
that this is so - he claims that he constructed us that way. Now you may
well mistrust my sources, but this is not the issue. The question is whether
you can *refute* my claim by appealing to Godel's theorem. From my point
of view there is no reason whatever for believing that we can give any
kind of evidence for the claim.