 The Wittgensteinian program favored by the Vienna Circle  (section 2.4  above) had collapsed in 1930. But Carnap soon recovered, and during a sleepless night on 21 January 1931, conceived of an entirely new basis for the Vienna Circle’s characteristic doctrines (Awodey &amp; Carus 2009). Instead of trying to fuse Hilbert and Wittgenstein, Carnap now dropped Wittgenstein altogether and pursued a Hilbertian approach. “Meaning” was no longer rooted in the correspondence between configurations of elementary facts and their linguistic representations. In fact, meaning was banished altogether, at least in our statements about the language of science (our metalinguistic “elucidations” such as those in the Tractatus itself or the Aufbau). The scientific language itself had empirical meaning, but how this was to be understood became a matter of dispute (the famous “protocol-sentence debate”) within the Vienna Circle (the sentences recording observations were called Protokollsätze by the Circle, which became “protocol sentences” in garbled English). This brought about a split in the Circle between a more realistic “right wing” (who adhered to something closer to Wittgenstein’s picture theory and held that once a state of affairs was “registered [konstatiert]” by an observer there could be no further doubt) and the “left wing” who followed Carnap in his new reference-avoiding syntax program (see Uebel 2007 on this debate). In any case our elucidations of the object language remain, in the new syntax framework, entirely within the linguistic realm; we are talking always and only about language. In logical syntax, we should be careful not to talk about “facts” or “things” but instead only about sentences or thing-names. We should restrict ourselves in principle to the “formal mode of speech” (sentences and names), employing the “material mode of speech” (facts and things) only for convenience, and when we are sure we can translate it into the formal mode. The (meta-)mathematical methods of Hilbert, Tarski, and Gödel were, in other words, to be extended to the whole of knowledge.