 Importantly, the left wing’s deflationary anti-metaphysics was accompanied by a distinctively constructivist attitude. Here one must hasten to add, of course, that what was constructed were not the objects of first-order discourse (tables, chairs, electrons and black holes) but concepts, be they concepts associated with technical terms for observables, theoretical terms or terms needed for reflection about the cognitive enterprise of science (ideas like evidence and its degrees and presuppositions). As meta-theorists of science they developed explications: different types of explications were envisaged, ranging from analytic definitions giving necessary and sufficient conditions in formal languages all the way to pragmatic, exemplar-based criterial delimitations of the central applications of contested concepts or practices. Two branches of the Circle’s constructivist tendency can thus be distinguished: Carnap’s rational reconstructions and formalist explications and Neurath’s and Frank’s empirically informed and practice-oriented reconceptualizations. The difference between these two approaches can be understood as a division of labor between the tasks of exploring logico-linguistic possibilities of conceptual reconstruction and considering the efficacy of particular scientific practices. In principle, the constructivist tendency in Vienna Circle philosophy was able to embrace both (compare Carnap 1934/37, §72 and Neurath 1936b). However, in its own day, this two-track approach remained incompletely realized as philosophical relations between Carnap and Neurath soured over disputes stemming from mutual misunderstandings. Frank’s final paper (1963) was a terse reminder that the logic of science was not the sole successor or replacement of traditional philosophy and Carnap’s response (1963b, §3) again acknowledged the compatibility in principle of his logic of science and what Frank called the “pragmatics of science” (1957). 