Naturalism is the incorrect philosophy of atheists. Its definition is "the philosophical belief that everything arises from natural properties and causes, and supernatural or spiritual explanations are excluded or discounted."
Naturalism explains how but not why. There are also many philosophical and logical problems with naturalism as it completely ignores the fine-tuning of the universe, the scientific principle of causality and would have people put their blind faith in the hypothesis of abiogenesis which is evidenceless. Naturalism would have everyone believe that the universe proceeded from nothingness.