1. A style and theory in art and literature that declares that things and people should be presented in a realistic manner; realism: Naturalism evolved as a belief in France in the 19th century when artists and writers endeavoured to depict things in a factual way, and not to make things look better than they were.
2. The philosophy that everything occurs from logical causes, whereas spiritual or supernatural reasons are ruled out; authenticity: Atheists, for example, believe in naturalism and that everything that exists is either physically or material.