 Neurath published four papers, one with Hahn (Neurath 1909a, 1909b and 1910a, and Hahn and Neurath 1909). Hahn separately published two others, the second submitted as her doctoral thesis (Hahn 1909 and 1910).In the joint paper, Hahn and Neurath proved the dependence of the principle of duality on the algebraic complementarity of domains of objects to which symbols and operations are applied. Neurath’s own three papers addressed mainly Schröder’s symbolic relation of equality and the property of commutativity of operations sum and product over symbols standing for classes of objects. It included a classification of applications of symbolic equalities and a discussion of univocality, or determinateness, noting its fundamental role in Schröder’s system and following the positivist philosopher Joseph Petzoldt’s discussion of causality, determinism and the interpretation of equality signs in mathematical equations. Neurath distinguished between (quantitative) equality, definitional equality and symbolic equality (Neurath 1910a). with the notational dimension of the latter equality and the lack of cognitive significance Neurath associated with differences in symbolic expression, his linguistic perspective differed markedly from Frege’s. Besides attention to the relativity of notational convention, the significance of the commutation law was, according to Neurath, relative to the axiomatic system (echoing Poincaré’s conventionalist treatment of geometry).