  What Neurath and (presumably) Carnap both missed was that Schlick’s thinking about meaning and linguistic significance had come a long way since his 1926 essay on “Experience, Cognition, and Metaphysics”, in which he tried to link Wittgenstein’s remarks about internal relations in the Tractatus with his own doctrine of implicit definition (Wittgenstein 1921, 4.122, 4.125, 4.1251, 5.232). There the goal was to apply both these ideas to the distinction between intuitions and concepts. The result was something of a disaster. For it implied what Schlick called “The Incommunicability of Contents”, the idea that any effort to communicate non-formal contents, like the greenness of the color green or the distinctive smell of wood smoke, must forever remain ineffable (Oberdan 1996, Sec. 2). But it was not long before Schlick’s efforts to explain linguistic meaning and scientific knowledge in terms of their ‘form’ and ‘content’ were abandoned and by the 1934–1935 academic year, he was developing what might well be called ‘a semantic conception’, spelled out in terms of grammars and the rules which constitute them, and presenting his new vision of language in his lectures on “Logik und Erkenntnistheorie” (Schlick 1934–5).