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Naturalism is an outgrowth of realism, a prominent literary movement in late 19th century France and elsewhere.
Naturalistic writers were influenced by the evolution theory of Charles Darwin. They believed that one's heredity and surroundings decide one's character. Whereas realism seeks only to describe subjects as they really are, naturalism also attempts to determine "scientifically" the underlying forces (i.e. the environment or heredity) influencing these subjects' actions. They are both opposed to romanticism, in which subjects may receive highly symbolic, idealistic, or even supernatural treatment. Naturalistic works often include uncouth or sordid subject matter. For example, Emile Zola's works had a frankness about sexuality along with a pervasive pessimism.
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