  Although Moritz Schlick (1882–1936) made a lasting mark in the philosophical memory by his role as the nominal leader of the Vienna Circle of Logical Positivists, his most lasting contribution includes a broad range of philosophical achievements. Indeed, Schlick’s reputation was established well before the Circle went public. In 1917, he published Space and Time in Contemporary Physics, a philosophical introduction to the new physics of Relativity which was highly acclaimed by Einstein himself as well as many others. The following year, the first edition of his influential General Theory of Knowledge appeared and, in 1922, he was appointed to the prestigious chair of Naturphilosophie at the University of Vienna. Upon his arrival at his new post, he immediately began to collaborate with the mathematician Hans Hahn, the sociologist and economist Otto Neurath, forming a discussion group known as the ‘Schlick Zirkel’. In the 1930s, the intellectual energy of the Circle was increased by newcomers like Rudolf Carnap and Kurt Gödel, as well as the outside influences of thinkers from America (Ernest Nagel, W. V. O. Quine), Britain (A. J.  Ayer), Poland (Alfred Tarski), and Germany (Hans Reichenbach), put Schlick in the midst of a virtual whirlwind of philosophical activity which deepened, broadened, and matured his thinking. As his international fame grew, Schlick found himself lecturing in London, teaching at Stanford, and receiving offers to join the faculties of prestigious universities both at home and abroad. At the same time, he produced a number of essays which exerted a deep and lasting influence on contemporary thought. But Schlick’s life was cut short by an assassin’s bullets in 1936, much to the loss of the intellectual world.