Naturalism is is a philosophical worldview and belief system that holds that there is nothing but natural things, forces, and causes.

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Naturalism holds that all concepts related to consciousness or to the mind refer to entities which are reducible to or supervene on natural things, forces and causes.

More specifically, it rejects the objective existence of any supernatural thing, force or cause, such as occur in humanity’s various religions, as well as any form of teleology.

It sees all "supernatural" things as explainable in purely natural terms. It is not merely a view about what science currently studies, but also about what science might discover in the future. Naturalism is a monistic and not a dualistic view of reality.

In practice, Naturalism reduces to the more specific ontological view of “scientific” naturalism, according to which reality consists only of what the concepts of the natural sciences (and especially physics) investigate.

"Scientific" naturalism is closely related to physicalism. It is often simply referred to as naturalism, religious naturalism or spiritual naturalism and occasionally as philosophical naturalism or ontological naturalism, though all those terms also have other meanings, in which naturalism often refers to methodological naturalism.