 Recent work on Hartmann has shown that he dealt with central twentieth century problems, such as the realism-antirealism debate, the reductionism-pluralism alternative, and with ways to resolve the “two cultures” divide that continues to torment contemporary philosophy (Peterson 2017; Peterson and Poli 2016; Hartung, Wunsch, and Strube 2012). His systematic and novel responses to these problems should be of interest to a contemporary audience, whatever their philosophical pedigree. The establishment of the  Nicolai Hartmann Society  has shown that scholars interested in Nicolai Hartmann and his ideas are present everywhere, not only in North America and Europe but also in South America and Asia. The proceedings of international conferences on Nicolai Hartmann (Poli, Scognamiglio, Tremblay 2011; Hartung, Wunsch, and Strube 2012; Peterson and Poli 2016; Peterson 2017b; Kalckreuth, Schmieg, and Hausen 2019) and this entry provide information on Hartmann’s thought that may facilitate a renewed evaluation of his contributions to philosophy.