Carnap's Aufbau and Pseudoproblems display the first explicit statement of what seemed an unprecedented attitude concerning realism. Around 1930 Wittgenstein explained a related doctrine to audiences in Vienna and Cambridge. Under the pressure of these two authorities, the view became a characteristically Viennese product in that it was widely accepted in Vienna and widely regarded as absurd most everywhere else. Kaila was expressing a not uncommon reaction among the non-Viennese when he spoke of the “catastrophic results” of Carnap's philosophy on that particular issue and observed that Carnap's ideas, if correct, “are apt to deprive even empirical research of its élan” (“Logistic Neopositivism” [1930], p. 4). Planck had raised similar charges against Machian positivism in “The Unity of the Physical World-Picture,” and in the early 1930s he thought he was witnessing a revival of the attempt to deny the existence of the external world (“Positivismus und reale Aussenwelt”).