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From: jeff@aiai.ed.ac.uk (Jeff Dalton)
Subject: Re: Putnam on Penrose
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Date: Tue, 29 Nov 1994 19:30:47 GMT
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In article <3bdkfs$4dg@newsbf01.news.aol.com> jrstern@aol.com (JRStern) writes:
>In <CzsDKp.3tu@cogsci.ed.ac.uk> jeff@aiai.ed.ac.uk (Jeff Dalton) writes:
><
>>        But - even
>>apart from the totally unjustified way this latter possibility is
>>dismissed - there is an obvious lacunae: the possibility of a program
>>we could write down but not succeed in understanding is overlooked!
>>
>>This is the mathematical fallacy on which the whole book rests.
>
>Now this puzzles me a bit.  There are some cases, and Penrose has
>overlooked one.  Suppose his conclusion follows in all the other
>cases.  Don't we then get this: if we understand the program, 
>Penrose is right?  Isn't that a significant conclusion in
>itself?
>>
>
>It's very significant.  It's just that Turing and Godel beat him
>to it by fifty years.

To what conclusion, exactly?  I just want to be sure I understand
what you're saying.

><
>Moreover, why can't Penrose "patch" his book by showing that
>it's implausible that the algorithm could be one we couldn't
>understand?
>>
>
>He could patch his book by saying Turing and Godel were right,
>but it would take all the sizzle, such as it is, out of his 
>writing.

But why can't Penrose "patch" his book by showing that
it's implausible that the algorithm could be one we couldn't
understand?  Then his anti-AI conclusion would follow
(ao far as Putnam's objection is concerened).  So why would
the sizzle depart?

><
>BTW, did anyone find the same flaw as Putnam earlier?  I don't
>want to go around saying "Putnam" all the time if in fact some
>other people made the same point.
>>
>
>As you might now guess, Turing and Godel found the thing that
>Putnam keeps pointing to.  About 20% of the messages on this
>newsgroup seem to be about this point.  Putnam points out how
>obvious this is.  I guess, even with his endorsement, it's 
>still not obvious enough.  Oh well.

I'm sorry, but how could Turing and Godel have determined
that Penrose omitted a case?  I'm asking whether anyone
other than Putnam pointed out that problem in Penrose's
book.

Now, what is it that you are calling "obvious" above?  It
may well be obvious that it's true, but I can't tell what
it is that you're referring to.

-- jeff



