Theodor Ziehen, the German psychologist and philosopher, was born in Frankfurt am Main and served as professor of psychiatry at the universities of Jena, Utrecht, Halle, and Berlin. He lived as a private scholar in Wiesbaden from 1912 to 1917, when he returned to teaching as professor of philosophy and psychology at the University of Halle. He retired in 1930.

Ziehen's viewpoint in epistemology is in the broadest sense positivistic. Knowledge must start with that which is experientially given, which Ziehen termed "becomings" (gignomene). From this "gignomenal principle" follows the "principle of immanence," according to which there is no such thing as metaphysical knowledge of the transcendental, and therefore it is nonsensical to want to know that which is not given. The first task of philosophy thus consists in seeking the laws of all that is given (the "positivistic" or "nomistic" principle). According to Ziehen, such a...