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Jul 26, 2010 at 20:07 comment added Joel David Hamkins As you suspected, you do need $\omega$-consistency here; mere consistency is insufficient, since if the theory has no $\omega$-model, then it could be that the theory proves the program halts only in nonstandard time. For example, the program that searches for a proof of a contradiction in PA is provably halting in $PA+\neg\text{Con}(PA)$, but it doesn't actually halt. But if the theory is $\omega$-consistent, then when it proves that a program halts, it really does halt.
Jul 22, 2010 at 4:21 history answered Richard Borcherds CC BY-SA 2.5