German logical empiricist philosopher and a leader of the European school of positivist philosophers known as the Vienna Circle.

After studies in physics at Heidelberg, Lausanne, Switz., and Berlin, where he studied with the German physicist Max Planck, Schlick earned his Ph.D. with a thesis on physics. His treatise, “Das Wesen der Wahrheit nach der modernen Logik” (1910; “The Nature of Truth According to Modern Logic”), reflected his scientific training and helped him obtain a teaching post at the University of Rostock in 1911. In 1922, after a year of teaching at Kiel, he became professor of the philosophy of inductive sciences at Vienna. There his disenchantment with earlier philosophies of knowledge crystallized, and he sought to establish new ways of ascertaining the nature of “how men know what they know,” by referring to the methods of the sciences.

The group of philosophers that gathered around Schlick at Vienna included Rudolf Carnap and Otto Neurath and the mathematicians and scientists Kurt Gödel, Philipp Frank, and Hans Hahn. Influenced by Schlick's predecessors in the chair of philosophy in Vienna, Ernst Mach and Ludwig Boltzmann, the Circle also drew on the work of philosophers Bertrand Russell and Ludwig Wittgenstein. The members of the Circle were united by their hostility to the abstractions of metaphysics, by the grounding of philosophical statements on empirical evidence, by faith in the techniques of modern symbolic logic, and by belief that the future of philosophy lay in its becoming the handmaiden of science.

As the reputation of the Circle grew through its books, journals, and manifestos, philosophers in other countries who were similarly inclined became familiar with one another's work. In 1929, as the movement for Logical Positivism began to expand, Schlick went to California briefly as a visiting professor at Stanford University. He continued to direct the Circle's activities and to write for its new review, Erkenntnis (Knowledge), from the time of his return to Europe until his death, which resulted from gunshot wounds inflicted by a deranged student.

Schlick was a prolific essayist and was the author of such books as Raum und Zeit in der gegenwärtigen Physik (2nd ed. 1919; Space and Time in Contemporary Physics, 1920); Allgemeine Erkenntnislehre (1918; “General Theory of Knowledge”); Fragen der Ethik (1930; Problems of Ethics, 1939); and the posthumous Grundzüge der Naturphilosophie (1948; Philosophy of Nature, 1949) and Natur und Kultur (1952).