 Like his younger contemporary, Ernst Cassirer, Natorp initially focused on the explication, defense, and elaboration of Cohen’s difficult and often impenetrable work on Kant-interpretation, the theory of science, and the history of  philosophy.[1]  While Natorp published important works of contemporary systematic philosophy (1887, 1888h), he devoted much of his attention in the last decades of the nineteenth century to filling out historical elements in Cohen’s larger framework. He especially employed his expertise in Greek thought to work out ancient anticipations of “critical” scientific philosophy, and analyze its natural development. Later, in the chaotic social, political, and cultural landscape of pre- and interwar Germany, and especially in the wake of Cohen’s death in 1918, Natorp departed from the classic Marburg concentration on the logic of the exact sciences. This departure was less a shift in his basic philosophical outlook than the sounding of new themes, some native to the Marburg School, others arising out of dialogue with other philosophers. Motivated by the liberal-socialist  ideals[2]  integral to the global theory of culture that was the Marburgers’ ultimate  aim,[3]  Natorp wrote widely on ethics, politics, and  Sozialpädagogik.[4]  On the other hand, one must also interpret Natorp’s later thought (esp. his “ontological turn”; von Wolzogen, 1988; Brach 1996) in light of his dialogue with other philosophies challenging neo-Kantianism’s dominance in the German academy, notably the so-called Lebensphilosophie, and the phenomenologies of Husserl and  Heidegger.[5] 