 As an aside, in the proof of the Löwenheim-Skolem theorem, specifically that part of the theorem in which one constructs a model for a satisfiable sentence, Löwenheim and Skolem’s tree construction was more or less the same as appears in Gödel’s thesis. In a 1967 letter to Hao Wang, Gödel takes note of the fact that his completeness proof had almost been obtained by Skolem in 1923. Though van Heijenoort and Dreben (Dreben and van Heijenoort 1986) remark that “Throughout much of the 1920s it was not semantic completeness but the decision problem for quantificational validity, a problem originating from the work of Schröder and Löwenheim, that was the dominant concern in studying quantification theory” (examples of such results would include the decision procedure for the first order monadic predicate calculus due to Behmann, (Behmann 1922)), according to Gödel, the reasons that Skolem did not obtain the complete proof are different and philosophically important, having to do with the then dominant bias against semantics and against infinitary methods: