 While he wrote at length and with significant originality on epistemology, ethics, aesthetics, philosophy of history, natural and social science, and many other topics, Hartmann’s central preoccupation was with developing a new ontology adequate to the changed scientific and humanistic intellectual landscape of the early twentieth century. Since Hartmann himself indicated 1919 as the year he finally broke through to what he called his “new ontology” (Harich 2000, 9), we could divide his voluminous work into two periods: an earlier Neo-Kantian inflected period, and a later period defined by the new ontology. But even this line is difficult to draw cleanly. The published works for his degree referred to above fall clearly into the earlier period, while some early essays, such as “Systematische Methode” (1912) and “Über die Erkennbarkeit des Apriorischen” (1914), already show signs of moving beyond the confines of the Marburg approach. The book Fundamental Philosophical Questions of Biology (Philosophische Grundfragen der Biologie, 1912) also stands out in this period as his earliest attempt to tackle the ontological issues contained in philosophy of biology. Here we will set aside the works of the earlier period.