First published in Germany in 1918, this acutely reasoned treatise attacks many of philosophy’s contemporary sacred cows, including the concept of metaphysics and Kant’s arguments for synthetic a priori knowledge. The book expounds most of the doctrines that would later be identified with the “classical period” of the Vienna Circle. Unlike many of his peers, Schlick displays a detailed and sensitive knowledge of the traditions he criticizes, displayed here in the chief work of this pioneering Viennese philosopher.