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Article 7466 of comp.ai.philosophy:
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Newsgroups: sci.logic,comp.ai.philosophy
Subject: Re: The Paradox of the Unexpected Hanging
Message-ID: <gm4FTB4w165w@CODEWKS.nacjack.gen.nz>
>From: system@CODEWKS.nacjack.gen.nz (Wayne McDougall)
Date: Thu, 29 Oct 92 18:52:39 NZST
References: <1992Oct21.141527.28698@oracorp.com>
Organization: The Code Works Limited, PO Box 10 155, Auckland, New Zealand
Lines: 44

daryl@oracorp.com (Daryl McCullough) writes:

> 
> Now, as John Baez said, the induction aspect working backward from
> Friday to Sunday is irrelevant. The heart of the paradox can be found
> in a simplified version where the judge says to the prisoner: "You
> will be executed today, but you will not be able to figure out that
> you will be executed today."
> 
> In this stripped-down form, it is clear that *if* the prisoner
> believes the judge, then the prisoner's beliefs are inconsistent: From
> the judge's first statement, the prisoner can conclude that he will be
> executed today. So the judge's second statement is a lie; the prisoner
> *does* figure out that he will be executed. Since the prisoner
> believes what is clearly a lie, the prisoner's beliefs are
> inconsistent.
> 
> On the other hand, if the prisoner does not believe the judge, then
> the judge is telling the truth. The prisoner cannot deduce that he
> will be hanged today, since he doesn't know whether the judge is
> telling the truth about the hanging.
> 
Excuse me, but it seems inappropriate to transform the judge's sentence 
into a self-contradictory statement. I would suggest that the judge's 
sentence is logical and consistent; the prisoner is at fault for 
incorrect application of backward induction.

I cannot see how you can transform "You will be hanged before Saturday, 
but the actual day will be a surprise" can be translated so that the 
judge is in that statement contradicting him/herself.

Rather, I would suggest that the prisoner CANNOT rule out Thursday 
because the assumptions in that elimination are contradictory to the 
assumptions made when Friday was eliminated.

And perhaps trying to tie this back to the topic a little - I don't see 
a conscious computer system having a problem with this in application 
of logic although most humans I know would!

-- 
  Wayne McDougall, BCNU
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