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Re: [ontolog-forum] Can Syntax be Semantic?

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Rob Freeman <lists@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 30 Jan 2010 12:28:17 +1300
Message-id: <7616afbc1001291528q51341c9elf96fc233aaff2dd1@xxxxxxxxxxxxxx>
Chris,    (01)

On Fri, Jan 29, 2010 at 3:16 PM, Christopher Menzel <cmenzel@xxxxxxxx> wrote:
>
> ...
> ...  On reflection, I will qualify my original claim that Russell's paradox 
>has *nothing* to do with
> undecidability.  For there is in fact a similarity between the usual argument 
>given in presentations
> of Russell's paradox and the method of diagonalization in computability 
>theory -- a method often
> used in proofs of undecidability.  Russell's argument can be used more 
>generally to show
> that, for any given set A, the set of all non-self-membered members of A 
>cannot itself be a
> member of A and the proof is a clear instance of diagonalization.  The 
>paradox itself ensues
> from this theorem if one also assumes (or one is able to prove) that there is 
>a universal set.
>
> So there is a similarity between the method of proof in Russell's paradox and 
>a common
> method of proof in computability theory.  But, conceptually, the paradox 
>itself has nothing
> to do with undecidability/incompleteness/computability per se.    (02)

I'm not sure what you mean by
"undecidability/incompleteness/computability per se."    (03)

I'm happy with your agreement that "there is in fact a similarity
between the usual argument given in presentations of Russell's paradox
and the method of diagonalization in computability theory -- a method
often used in proofs of undecidability."    (04)

-Rob    (05)

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