 Gödel revealed his results to Carnap in Vienna on 26 August 1930, and announced his result (the first theorem) in a casual discussion remark in the famous Königsberg Conference on September 7, 1930. John von Neumann, who was in the audience and was at the time working in the context of Hilbert’s program, immediately understood the great importance of the result. On 20 November he wrote a letter to Gödel on a “remarkable” corollary of Gödel’s result he had discovered: the unprovability of consistency (the second theorem). Meanwhile Gödel himself, however, had found the same idea and had already sent the final version of his article, which now contained also a statement of the second incompleteness theorem, for publication. The article was published in January 1931 (Gödel 1931; helpful introductions to Gödel’s original paper are Kleene 1986 and Zach 2005). The word quickly started to spread of these results which apparently had great importance for the foundations of mathematics—though views on what really was the moral varied. Paul Bernays, perhaps the most important collaborator of Hilbert, showed great interest in the results, though he first had difficulties in understanding them properly. His active correspondence with Gödel also shows that Gödel was already at the time fully aware of the undefinability of truth.