Re: wittgensteins Tractarian logic any suggestions.?

On 28 Mar 2007 10:16:13 -0700, "translogi" <wilemien@xxxxxxxxxxxxxx> wrote:


I still want to find time to study Post on truth tables as well.

I read it briefly and also in his article there seems to be a mixing
up from logic and meta-logic.

Little wonder. That distinction wasn't (clearly) made at that time.


P & (P -> Q) -> Q
but also
|- P and |- P -> Q implies |- Q

the first is logic
the second meta logic

Yes.


(in a proof theoretic scheme)
in a model theoretic scheme does this difference exist?

Sure. There we would state:

|= P and |= P -> Q implies |= Q.


Finally for FOPL (with or without identity) we can state the (Meta-)Theorem:

|= A iff |- A for any wff A.

Gödel's first notable contribution to logic! (1930 btw.)


F.

--

E-mail: info<at>simple-line<dot>de
.