In philosophy, physicalism is the metaphysical 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.
Physicalism is closely related to materialism. Physicalism grew out of materialism with advancements of the physical sciences in explaining observed phenomena. The terms are often used interchangeably, although they are sometimes distinguished, for example on the basis of physics describing more than just matter (including energy and physical law).
According to a 2009 survey, physicalism is the majority view among philosophers, but there remains significant opposition to physicalism. Neuroplasticity is one such evidence that is used in support of a non-physicalist view. The philosophical zombie argument is another attempt to challenge physicalism.