Re: My investigations into Godels Incompleteness Theorem
- From: stevendaryl3016@xxxxxxxxx (Daryl McCullough)
- Date: 26 Sep 2006 05:01:29 -0700
John Jones says...
Thankyou for your well-received explanation which I read slowly and
understood. Can you say what happens next please?
That depends on whether you agree with the fixed point lemma,
or not. The route to Godel's incompleteness theorem has the
following parts:
1. Establish a correspondence between sentences (about arithmetic,
in the case of Godel, or about strings, in our variant) and objects
in the domain of discourse (natural numbers, in Godel's case, strings
in ours).
2. Establish the fixed point lemma. In Godel's case, for every formula
Phi(x) in the language of arithmetic, there is a sentence S in the
language of arithmetic such that S is true if and only if Phi holds
of the natural number corresponding to S. In our variant, for every
property P of strings, there is a sentence S such that S is true if
and only if the string corresponding to S has property P.
3. Establish that theoremhood is definable. In Godel's case, that
means coming up with a formula Provable(x) in the language of
arithmetic such that for any sentence S, S is provable from the
axioms of PA if and only if Phi holds of the natural number
corresponding to S. For our variant, we would find a property
"is provable" of strings such that for any sentence S, S is a
theorem if and only if the string corresponding to S has the
property "is provable".
4. Use the fixed point lemma to come up with a sentence S such that
S is true if and only if the natural number (or string, in our case)
corresponding to S satisfies the property of not being a the code of
a theorem.
--
Daryl McCullough
Ithaca, NY
.
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