Naturalism is a late-19th-century literary movement that applied scientific determinism to fiction, treating characters as products of heredity and environment.
Naturalism began with Émile Zola in France in the 1870s, particularly his vast Rougon-Macquart cycle of twenty novels (1871–1893), which traced one family across generations to demonstrate his thesis that human behaviour is determined by biology and social conditions. Zola's preface 'Le Roman expérimental' (1880) borrowed the language of medicine — the novelist as experimenter, characters as specimens. The movement spread quickly: Frank Norris and Theodore Dreiser in America, Thomas Hardy in England, Émile Zola's German and Russian disciples. Naturalist novels are often grim and unflinching — alcoholism, prostitution, factory labour, and class fatalism are constant subjects — because the underlying belief is that pretending otherwise would falsify reality. The movement faded after 1914 but its spirit survives in social-realist fiction, true crime, and serious documentary.