Some Unpublished Letters by Gödel and von Neumann in the Fraenkel Archive

Several letters by Kurt Gödel and Johann (János) von Neumann from the (so far uncatalogued) archive of Abraham (Adolf) Fraenkel at the National Library of Israel are published and discussed. These include two fragments by Gödel of special interest, since they concern the relationship between Gödel’s incompleteness theorem and work by Herbrand, Presburger, and Zermelo, as well as a long letter from von Neumann from 1923 explaining his own approach to the axiomatization of set theory.