My task is exclusively to bear witness to how penetrating Ernst Mach's influence already was before the year 1922 when Moritz Schlick formed the so-called "Vienna Circle". It so happens that I studied in my own hometown Vienna precisely three years from 1918 until 1921, and that what passed for philosophical discussion revolved essentially around Mach's ideas. Vienna as a whole was already extraordinarily inclined toward philosophy of natural science.² Apart from Heinrich Gomperz,³ Adolf Stöhr⁴ also taught in Vienna and both men followed a similar line, and Robert Reininger⁵ was at the very least friendly toward such an outlook.