The early history of the Vienna Circle began around 1907 with a discussion group in a Viennese café, about which Philipp Frank (1949a, 1–52) reports at length. This illustrious circle included Catholic philosophers, romantic mystics, and, alongside Frank, Otto Neurath, Hans Hahn, and Richard von Mises. Stimulated by Mach and taking the allegations of the unscientific nature of philosophy as a given, discussions were held about a synthesis of empiricism and symbolic logic, as well as about Brentano, Meinong, Husserl, Schröder, Helmholtz, Hertz, and Freud. The intention was to update Mach's empiricism with French conventionalism (Duhem, Poincaré) and thus also to counter Lenin's opposition to "empirio-criticism.' In the persons of Hahn, Frank, and Neurath this heterogeneous coffee-house circle constituted the original core of the later Vienna Circle, with which the younger scientists of the Schlick circle began to associate after World War I. After 1924 the meetings of the Vienna Circle proper were held regularly on Thursdays at Vienna's Boltzmanngasse 5.