[FOM] Inconsistency of P
Panu Raatikainen
panu.raatikainen at helsinki.fi
Mon Oct 3 00:49:27 EDT 2011
"Monroe Eskew" <meskew at math.uci.edu>:
> Suppose S is a subtheory of T, and n is such that S proves K(n)>c.
> Then P outputs some m, where m is the *first* one seen by P, not
> necessarily equal to n. Hence, T proves K(m)<c and K(m)>c, so it is
> inconsistent. Now if S is sufficiently strong (so that it is Sigma_1
> complete), then S proves K(m)<c. However, this does not mean that S
> proves K(n)<c, because the witness showing K(m)<c is a proof in T, not
> necessarily in S. So it might take a more complex program to actually
> output n. The Chaitin machine for S could work, but this might be
> longer than c.
"K(n)<c" is a Sigma_1 sentence.
If "K(n)<c" is true, and S is Sigma_1 complete, then S proves
"K(n)<c". Period.
That is what Sigma_1 completeness is.
I am afraid I fail to see how any involved Chaitin machine
considerations (or whatever) could change that...
Best
Panu
--
Panu Raatikainen
Ph.D., University Lecturer
Docent in Theoretical Philosophy
Theoretical Philosophy
Department of Philosophy, History, Culture and Art Studies
P.O. Box 24 (Unioninkatu 38 A)
FIN-00014 University of Helsinki
Finland
E-mail: panu.raatikainen at helsinki.fi
http://www.mv.helsinki.fi/home/praatika/
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