In philosophy,
physicalism is the
ontological thesis that "everything is physical", that there is "nothing over and above" the physical, or that everything
supervenes on the physical. Physicalism is a form of ontological
monism—a "one
substance" view of the nature of reality as opposed to a "two-substance" (
dualism) or "many-substance" (
pluralism) view. Both the definition of "physical" and the meaning of physicalism have been debated.