In metaphysics, physicalism is the view that everything is physical, that there is nothing over and above the physical, and that everything supervenes on the physical. It stands in direct opposition to idealism, which asserts that reality arises from the mind. Physicalism is a form of ontological monism—a single-substance account of the nature of our universe's reality, in contrast to "two-substance" or "many-substance" (pluralist) views. Physicalism is closely related to naturalism, though important distinctions exist between them.