On the question of God, both religious and non-religious thinkers typically regard naturalism as the obvious and primary way to challenge supernaturalism. Naturalism is distinctive among philosophical worldviews for its reliance on the sciences. Other chapters recount how developments in specific scientific fields, such as biology, affected the intellectual climate around the question of God’s existence. Naturalism’s own role also deserves to be told. Naturalism as a comprehensive worldview only congealed during the late nineteenth and twentieth centuries, and confronted God with the staunchest atheist philosophy to ever challenge supernaturalism. Modern naturalism elevated four main approaches to prominence for refuting supernaturalism: (1) scientific theorizing is genuinely explanatory, while religion is not; (2) nature’s energies are causally closed, forbidding divine interaction; (3) scientific skepticism is warranted toward alleged revelations and miracles; and (4) naturalistic theories explaining religion’s origin and function need no deities.