In On the Cognition and Sensation he undertakes to erase the traditional sharp division between the mental and the physical in two specific ways: First, he advances a theory that minds and mental conditions consist in forces [Kräfte] that manifest themselves in people’s bodily behavior—just as physical nature involves forces that manifest themselves in the behavior of bodies. Officially, he remains agnostic on the question of what force is, except for conceiving it as something apt to produce a