Hartmann was born, of German descent, in Riga, now Latvia and then capital of the Russian province of Livonia. He studied Medicine at the University of Tartu (then Jurjev), then Philosophy in St. Petersburg and, most importantly, at the University of Marburg in Germany, where he took his Ph.D. and Habilitation. He was professor of philosophy in Marburg (1922–25), Cologne (1925–31), Berlin (1931–45) and Göttingen (1945–50), where he died.

Originally a Marburg Neo-Kantian, studying under Hermann Cohen and Paul Natorp, Hartmann developed his own philosophy which has been variously described as a variety of existentialism or critical realism. Hartmann suffered from the comparison with his popular Marburg successor Martin Heidegger, whose vision of ontology was considerably broader than Hartmann’s.

Among Hartmann’s many students were Boris Pasternak, Hans-Georg Gadamer and Delfim Santos. He is the modern discoverer of emergence — originally called by him categorial novum. His encyclopedic work is basically forgotten today, although famous during his lifetime. His early work in the philosophy of biology has been cited in modern discussions of genomics and cloning, and his views on consciousness and free will are currently in vogue among contributors to the Journal of Consciousness Studies