Nov 26, 2012
Godel Work to Show the Un-Success of Hilbert's Program_Documented by Marsigit
Gödel showed Hilbert's Program can not succeed. This was proven in what is now called Gödel's Incompleteness Theorem:
Let S be a formal system for number theory. If S is consistent, then there is a sentence, G, such that neither G nor the negation of G (written G) is a theorem of S. Thus, any formal system sufficient to express the theorems of number theory has to be incomplete.
S can prove P(n) just in case n is the Gödel-number of a theorem of S. There exists k, such that k is a Gödel-number of the formula P(k)=G. This statement says of itself, it is not provable. Even if we define a new formal system S = S + G (thus including the undecidable theorem as an axiom), we can find G which isn't provable in (is independent of) S. The reasoning Gödel used for his incompleteness theorem is finitary, so it could be formalized inside S. Thus, S can prove that if S is consistent, then G is not provable. Note that the underlined phrase is what G says, so S proves Cst(S) implies G is true, but G says G is not provable. Suppose S can prove Cst(S), then S can prove G, but if S is consistent, it can't prove G, thus it can't prove its consistency. Thus, Hilbert's Program does not work; one cannot prove the consistency of a mathematical theory.