  To what extent has proof theory achieved its original aims? For  Hilbert, the aims were a complete clarification of the foundational  problems through finitary proofs of consistency, etc, aims in which  proof theory failed. Hilbert in his program was not interested in the study of mathematical proofs in themselves, but only in clearing the  central foundational problems (and then to forget about them). A  recently found note by Hilbert gives a different picture: the note  states that Hilbert wanted to add as a 24th and last problem in his  famous Paris list of open mathematical problems of 1900 the  development of “a theory of proof methods in  mathematics”. This was before his metamathematical program for  the development of a proof theory emerged.