Naturalism in literature (from Wikipedia): “Naturalism was a literary movement or tendency from the 1880s to 1940s that used detailed realism to suggest that social conditions, heredity, and environment had inescapable force in shaping human character. It was a mainly unorganized Literary movement that sought to depict believable everyday reality, as opposed to such movements as Romanticism or Surrealism, in which subjects may receive highly symbolic, idealistic, or even supernatural treatment.”
From Keywords: “Naturalism is now primarily a critical term of literature or of art, but it is a more complex word, as its history indicates, than is usually realised. It first appeared in English, from C17, as a term in religious and philosophical argument. It had been preceded by naturalist, in the same context, from C16. It followed a particular sense of Nature in which there was a contrast with God or spirit. To study the natural causes of events, or to explain or justify morality form nature or human nature, was to be a naturalist and to propound naturalism, although the actual terms seem to have been conferred by their opponents… Naturalist was a common C17 term for natural philosopher, or as we would now say Scientist: in practice those we would now call physicists or biologists…
(From C19) Naturalism in the general philosophical and scientific sense (was) much influence by the new and controversial developments in geology and biology and especially by Darwin’s theory of natural selection in Evolution. The school of naturalisme in France was especially affected , as in Zola, but the idea of the application of scientific method in literature: specifically the study of heredity in the story of a family, but also, more generally, in the sense of describing and interpreting human behaviour in strictly natural terms, excluding the hypothesis of some controlling or directing force outside human nature.”
Related article on Naturalism in American literature.