Thomas Meier (MCMP/LMU) gives a talk at the MCMP workshop "Influences on the Aufbau" (1-3 July, 2013) titled "Influences on Carnap's Structuralism in the Aufbau". Abstract: I present an analysis of the different influences on Carnap’s structuralism in the Aufbau. First, I show how Hilbert’s notion of implicit definition from his axiomatization of Euclidean geometry (Hilbert, 1899) had an influence on Carnap’s development of his notion of purely structural description. As one further point, I will also discuss Neo-Kantian influences on Carnap’s structuralism. This mainly concerns Carnap’s posi- tion of what has been identified as a form of epistemic structural realism in the modern literature (see Frigg & Votsis, 2011). I will argue that Carnap’s proposal for individuating certain relations as founded relations in §154 is of contemporary relevance for actual debates on the so-called Newman-Objection. The Neo-Kantian influence on Carnap’s epistemology becomes clearer if we consider his purely relational system of knowledge, in which objects are subordinate to relations, to the Grundrelationen. For Carnap, a Kantian thing-in-itself as such would not be knowable but through its relations.