 Paul Gerhard Natorp was one of the most prominent philosophers in Germany at the turn of the last century. Born in Düsseldorf on January 24, 1854, he began his university education at Bonn in classical philology under Hermann Usener, and continued at the University of Strassburg, but as he neared completion of his studies, he found himself unsatisfied with his work, and vexed by “a secret philosophical urge” (Natorp 1921f: 152–153; all translations by the author). It found its outlet when a friend studying at Marburg wrote to him of Hermann Cohen and F.A. Lange, and of their interpretation of Kant; thenceforth Natorp “placed his whole thinking and his entire, powerful capacity for work in the service of this single task:” the development of “philosophy as science” (Cassirer 1925: 276). His first philosophy teacher was Ernst Laas, whose anti-Kantian and anti-Platonic positivism incited Natorp to deeper engagement with the philosophy of critique (Natorp 1921f: 153). In this way, his early philosophical studies converged with his original love of philology as he pursued the “prehistory” of Kantian critique in Descartes, Galileo, and Copernicus, back to Plato (Natorp 1921f: 154). Natorp completed his Habilitation under Cohen at Marburg in 1881, and taught there until his death on August 17, 1924.