Quick Definition: Everything arises from natural causes
Naturalism is “the philosophical belief that everything arises from natural properties and causes, and supernatural or spiritual explanations are excluded or discounted.”Adherents of naturalism (i.e., naturalists) assert that natural laws are the rules that govern the structure and behavior of the natural universe, that the changing universe at every stage is a product of these laws.
“Naturalism can intuitively be separated into a [metaphysical] and a methodological component.” Metaphysical here refers to the philosophical study of the nature of reality. Some philosophers equate naturalism with materialism. For example, philosopher Paul Kurtz argues that nature is best accounted for by reference to material principles. These principles include mass, energy, and other physical and chemical properties accepted by the scientific community. Further, this sense of naturalism holds that spirits, deities, andghosts are not real and that there is no “purpose” in nature. Such an absolute belief in naturalism is commonly referred to as metaphysical naturalism.
In contrast, assuming naturalism in working methods, without necessarily considering naturalism as an absolute truth with philosophical entailments, is called methodological naturalism. The subject matter here is a philosophy of acquiring knowledge.
With the exception of pantheists—who believe that Nature and God are one and the same thing—theists challenge the idea that nature contains all of reality. According to some theists, natural laws may be viewed as so-called secondary causes of god(s).
In the 20th century, Willard Van Orman Quine, George Santayana, and other philosophers argued that the success of naturalism in science meant that scientific methods should also be used in philosophy. Science and philosophy are said to form a continuum, according to this view.