 Summing up, Schröder constructed an algebraic version of modern predicate logic and also a theory of relations. He applied it to different fields (e.g., Cantor’s set theory), and he considered his algebraic notation as a general or universal language (pasigraphy, see Peckhaus 2004 and Legris 2012). It is to be noted that Löwenheim in 1940 still thought it was as reasonable as set theory. According to him, Schröder’s idea of solving a relational equation was a precursor of Skolem functions, and Schröder inspired Löwenheim’s formulation and proof of the famous theorem that every “arithmetical” sentence with an infinite model has a countable model. Schröder’s calculus of relations was the basis for the doctoral dissertation of Norbert Wiener (1894–1964) in Harvard (Wiener 1913). According to Brady, Wiener gave the first axiomatic treatment of the calculus of relations, preceding Tarski’s axiomatization by more than twenty years (see Brady 2000: 165).