  Nor was it long before Space and Time … was succeeded by the first edition of Schlick’s General Theory of Knowledge. During the same period, Schlick spent a year engaged in war work at Aldershof airport outside Berlin followed, in 1921, by an appointment at Kiel. Since rumors were already spreading about a possible appointment at Vienna, Schlick’s family stayed in Rostock until 1922, when they moved to Vienna where he assumed the Chair of Naturphilosophie which had previously been occupied by Ernst Mach and Ludwig Boltzmann (v. d. Velde-Schlick 2008; Ferrari 2009). Schlick’s selection for the post was probably initiated by the mathematician Hans Hahn and the physicist Phillip Frank, with a strong recommendation from Einstein. When Schlick arrived in Vienna, he immediately became involved with Hahn and Frank, as well as the economist Otto Neurath, in their Thursday night discussion meetings in the Chemistry Building of the University of Vienna. Schlick was a welcome addition to the group, and together they formed the core of what would later become known as ‘the Vienna Circle’ (Uebel 2003). Philosophy would never be the same.