In 1921 the chair in the tradition of Mach and Boltzmann became vacant as a result of Adolf Stöhr's (On Adolf Stöhr's life and work, cf. Austeda (ed.) 1974) death. During World War I, the latter had ensured a certain continuity of scientific, language-critical philosophy. The first chair had not been occupied again since Friedrich Jodl's death in 1914. The mathematician Hans Hahn returned to Vienna accepting a full professorship for mathematics at the University of Vienna. Hahn sought to continue the debates of the proto-circle in the pre-war years and backed the appointment of Moritz Schlick (1882–1936) to the chair for natural philosophy. His efforts proved successful in spite of considerable resistance in 1922.