Scientific naturalism is the conjunction of naturalism—the claim that nature is all that there is and, hence, that there is no supernatural order above nature—with the claim that all objects, processes, truths, and facts about nature fall within the scope of the scientific method. This ontological naturalism implies weaker forms of naturalism, such as the belief that humans are wholly a part of nature (anthropological naturalism); the belief that nothing can be known of any entities other than nature (epistemological naturalism); and the belief that science should explain phenomena only in terms of entities and properties that fall within the category of the natural, such as by natural laws acting either through known causes or by chance (methodological naturalism). Before the late nineteenth century, scientific naturalism was not the dominant way of understanding the world, nor is it in the late twentieth century the only metaphysical position consistent with modern science. Technically, scientific naturalism is not the same thing as philosophical materialism, which is the belief that everything is ultimately material, but it is closely related, and today they are usually conflated. Traditional theists do not accept scientific naturalism, although they may agree with anthropological naturalism and/or methodological naturalism.
Collins, Robin, "Scientific Naturalism" (2000). Philosphy Educator Scholarship. 47.