 Neurath’s logic writings focused on Schröder’s axiomatic systematization of algebraic logic, mainly in the monumental Vorlesungen über die Algebra der Logik (exakte Logik) (1890-95). There and in earlier writings, Schröder geve a fundamental role to the relation of subsumption and a law of duality. Subsumption was a part-whole relation defined over domains of objects and it was expressed with a symbol, €, which denoted both inclusion and equality (with a corresponding algebraic expression, following Hermann Grassmann, in terms of partial inequality ≤) so that if a € b and b € a, then a=b. The law of duality established a systematic correspondence between theorems in terms of 1 and operation + and theorems in terms of 0 and operation x. The methodological role of duality organizing and deriving theorems was expressed in a dual-column presentation. The latter was adopted in a more general spirit by Neurath and subsequently also by Carnap in his presentation of the systematic correspondence between formal and material modes (see Cat 2019).