ORIGINAL PAPER An Introduction to Nicolai Hartmann’s Critical Ontology Keith R. Peterson Received: 1 October 2011 / Accepted: 14 February 2012 / Published online: 29 February 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Nicolai Hartmann contributed significantly to the revitalization of the discipline of ontology in the early twentieth century. Developing a systematic, post- Kantian critical ontology ‘this side’ of idealism and realism, he subverted the widespread impression that philosophy must either exhaust itself in foundationalist epistemology or engage in system-building metaphysical excess. This essay pro- vides an introduction to Hartmann’s approach in light of the recent translation of his early essay ‘How is Critical Ontology Possible?’ (1923) In it Hartmann criticizes both the pretensions of epistemology as well as the principal errors of classical ontology, and he proposes a series of correctives that lead to his development of a highly original and elaborate stratified categorial ontology. This introduction explains the most important errors of the ‘old’ ontology, his correctives to them, and further fleshes out these correctives with reference to his mature ontological work. Keywords Categories Á Critical ontology Á Critique Á Epistemology Á Ideal being Á Logicism Á Nicolai Hartmann Á Ontology Á Real being Á Reductionism Á Spheres of being Á Stratification Á Teleology In a recently published book, the late Wolfgang Harich staged a series of dialogues between himself and the fictive interlocutor Paul Forster, in the course of which he attempted to come to terms with the ‘‘greatness’’ (in both extent and value) as well as the ‘‘limitations’’ of Nicolai Hartmann’s philosophy (Harich 2004). 1 The eighth K. R. Peterson (&) Department of Philosophy, Colby College, 4550 Mayflower Hill, Waterville, ME 04901-8840, USA e-mail: Keith.Peterson@colby.edu URL: http://www.colby.edu/directory_cs/krpeters/ 1 The book is subtitled ‘‘Attempt at a Marxist Self-Understanding,’’ or, a bit more expansively, ‘‘An Attempt to Reconcile Hartmann with my version of Marxism.’’ Harich was, perhaps paradoxically, a life- long follower and friend of Georg Luka ´cs, as well as a great admirer and former student of Hartmann in 123 Axiomathes (2012) 22:291–314 DOI 10.1007/s10516-012-9184-1