[FOM] Godel, Wittgenstein etc.

Torkel Franzen torkel at sm.luth.se
Wed May 7 04:09:55 EDT 2003

Neil says:

 >There is no need for any talk of truth when proving the Godel-sentence
 >G for F. It suffices either 
 >(i) to assume, in meta-F, that F is consistent; or 
 >(ii) to extend F with a reflection principle (but with no new
 >extra-logical vocabulary) so as to be able to prove G.

 Certainly there is no (essential) need for talk of truth when proving
"if F is consistent then G". Talk of truth is here just a matter of
convenience. But in your paper you are concerned with a "semantical
argument...designed to help one understand why asserting G would be
the right thing to do". If a proof of "if F is consistent then G"
is to prompt us to assert G, we must take the view that asserting "F
is consistent" is the right thing to do. It is here that any "need"
for talk of truth must be located. Hence my complaint about your
paper, that we already knew that G can be deduced from "F is
consistent" without invoking truth, and that the real issue concerns
how "F is consistent" (or, equivalently, your reflection principle) is
to be justified.

Torkel Franzen

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