Page "Tarski's undefinability theorem" Paragraph 5

The undefinability theorem is conventionally attributed to Alfred Tarski.

Gödel also discovered the undefinability theorem in 1930, while proving his incompleteness theorems published in 1931, and well before the 1936 publication of Tarski's work ( Murawski 1998 ).

While Gödel never published anything bearing on his independent discovery of undefinability, he did describe it in a 1931 letter to John von Neumann.

Tarski had obtained almost all results of his 1936 paper Der Wahrheitsbegriff in den formalisierten Sprachen between 1929 and 1931, and spoke about them to Polish audiences.

However, as he emphasized in the paper, the undefinability theorem was the only result not obtained by him earlier.

According to the footnote of the undefinability theorem ( Satz I ) of the 1936 paper, the theorem and the sketch of the proof were added to the paper only after the paper was sent to print.

When he presented the paper to the Warsaw Academy of Science on March 21 1931, he wrote only some conjectures instead of the results after his own investigations and partly after Gödel's short report on the incompleteness theorems " Einige metamathematische Resultate über Entscheidungsdefinitheit und Widerspruchsfreiheit ", Akd.

der Wiss.

in Wien, 1930.