Hartmann was born a Baltic German in Riga, which was then the capital of the Governorate of Livonia in the Russian Empire, and which is now in Latvia.

He was the son of the engineer Carl August Hartmann and his wife Helene, born Hackmann.

In 1912 he published Die philosophischen Grundfragen der Biologie (The Philosophical Foundations of Biology).

The unrest of the National Socialist period seems to have left Hartmann relatively undisturbed in his task of developing a new ontology.

In the "'-Dossiers über Philosophie-Professoren" (i.e. SD-files concerning philosophy professors) that were set up by the SS Security Service (SD) Nicolai Hartmann was classified from an SS-point of view in the following way: "has always been a nationalist.

His works Teleologisches Denken (Teleological Thinking) (1951) and Ästhetik (Aesthetics) (1953) were published posthumously.

He is regarded as an important representative of critical realism and as one of the major metaphysicians of the twentieth century.

Among Hartmann's many students were Boris Pasternak, Hans-Georg Gadamer, Emil Cioran, Jakob Klein, Delfim Santos and Max Wehrli.

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[when?]

[6][7] This science involves studying the most general characteristics of entities, usually referred to as categories, and the relations between them.

This has the consequence that all positive and all the negative modalities fall together: whatever is possible is both actual and necessary, whatever is not necessary is both non-actual and impossible.

The values inhabiting this realm are unchanging, super-temporal, and super-historical, though human consciousness of them shifts in focus over time.

For Hartmann, this means that our awareness of the value of a state of affairs is not arrived at through a process of reasoning, but rather, by way of an experience of feeling, which he calls valuational consciousness.

As such, Hartmann's conception of proper moral philosophy contrasts with rationalist and formalist theories, such as Kant's, according to which ethical knowledge is derived from purely rational principles.