Metaphysical naturalism

Metaphysical naturalism, also known as ontological naturalism, philosophical naturalism, or antisupernaturalism, is a worldview asserting that only natural elements, principles, and relations—of the kind examined by the natural sciences—exist. It rejects supernatural concepts and explanations found in many religions. Methodological naturalism serves as a philosophical foundation for science, though scholars disagree on whether it necessarily assumes metaphysical naturalism or can rest on other ontological bases.

As Carl Sagan put it, "The Cosmos is all that is or ever was or ever will be." Arthur C. Danto described naturalism as a form of philosophical monism where everything that exists or happens is natural, meaning it can be explained through methods continuous across domains, paradigmatically those of the natural sciences. Naturalism thus repudiates any entities that lie, in principle, beyond scientific explanation. David Papineau traced the modern use of "naturalism" to early 20th-century American philosophers like John Dewey, Ernest Nagel, Sidney Hook, and Roy Wood Sellars. He noted that most contemporary philosophers accept this broad characterization—rejecting supernatural entities and allowing science as a possible route to truths about the human spirit—though philosophers of religion are less enthusiastic. Despite its popularity, if construed more narrowly, some philosophers (e.g., John McDowell, David Chalmers, Jennifer Hornsby) would be excluded, but many remain content with a higher bar. Alvin Plantinga, a critic, observed that while naturalism is not a religion, it performs a similar cognitive function by providing answers to deep human questions.

Metaphysical naturalism underpins science. Kate and Vitaly (2000) described its assumptions: reality is objective and consistent, humans can perceive it accurately, and rational explanations exist for real-world elements. Steven Schafersman argued that methodological naturalism adopts philosophical naturalism within science as a strategy or working hypothesis, regardless of whether one fully believes it; science does not depend on the ultimate truth of any metaphysics, but must proceed as if nature is all there is.

Contemporary metaphysical naturalists hold diverse beliefs, though most adopt some form of materialism or physicalism. Under this view, natural phenomena like the Big Bang, solar system formation, abiogenesis, and evolution occur without supernatural influence. The mind is considered a natural phenomenon; naturalists reject souls, spirits, ghosts, and substance dualism. W. T. Stace concluded that if identity and personhood are entirely natural products, then cognitive sciences can explain how cultural and psychological phenomena—religion, morality, language—evolved, and consciousness itself is subject to evolutionary principles. Naturalists hold that intelligence refines naturally evolved faculties, and that to increase true beliefs, one should perfect and consistently employ reason, with empirical methods (especially scientific ones) being unsurpassed for discovering facts, while pure reason alone can uncover logical errors. Immateriality, being unprocedural and unembodiable, is considered indistinguishable from nothingness.