Re: What isn't a tautology?

Chris Menzel wrote:
> On 16 Jul 2005 17:01:29 -0700, Michael De <mikejde@xxxxxxxxx> said:
> > Chris Menzel wrote:
> >> On 16 Jul 2005 06:35:12 -0700, Michael De <mikejde@xxxxxxxxx> said:
> >> > ...
> >> >> Point in this context being...?
> >> >
> >> > Just that there is an "analytic" method for constructing an equivalent
> >> > formula whose validity we can test by the truth table method and such
> >> > that A is valid iff A* is tautologous.
> >>
> >> There can be no such method (assuming A here ranges over all the
> >> sentences of a first-order languauge).
> >
> > Do you mean that Smullyan's fundamental theorem is a hoax?
>
> I suspect the more likely explanation is that you've misunderstood it.
> If I'm reading you right, you are claiming that Smullyan's theorem gives
> us an effective method for determining, for any formula A of predicate
> logic, whether or not A is valid. By Church's Theorem, there can be no
> such method.

No! I said that for any *valid* A.

.

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