 In 1930, considerations of this sort appeared to receive a considerable boost due to Waismann’s reports of Wittgenstein’s meetings with him and Schlick. Wittgenstein had discussed the thesis “The sense of a proposition is [the method of] its verification” in conversations with Schlick and Waismann on 22 December 1929 and 2 January 1930 (see Waismann 1967 [1979, 47 and 79]) and Waismann elaborated it in his “Theses” which were presented to the Circle as Wittgenstein’s considered views. While Wittgenstein appears to have thought of his dictum primarily as a constitutive principle of meaning, in the Circle it was put to work mainly as a demarcation criterion against metaphysics. Whether it was always noted that Wittgenstein’s thesis and the criterion of cognitive significance must be distinguished (the former entails the latter, but not vice versa) may be doubted, but striking differences emerged all the same. Like Carnap’s criterion of significance of 1928, the version of the criterion which followed from Wittgenstein’s dictum also allowed for verifiability in principle (and did not demand actual verifiability): like Carnap’s notion of experiential support, it worked with the mere conceivability of verifiability. Yet Wittgenstein’s criterion required conclusive verifiability which Carnap’s did not. (The demand for conclusive verifiability was discussed in the meetings with Wittgenstein.) By 1931, however, it had become clear to some that this would not do. What Carnap later called the “liberalization of empiricism” was underway and different camps became discernible within the Circle. It was over this issue that the so-called “left wing” with Carnap, Hahn, Frank and Neurath first distinguished itself from the “more conservative wing” around Schlick. (See Carnap 1936–37, 422 and 1963a, §9. Carnap 1936–37, 37n dated the opposition to strict verificationism to “about 1931”.)