in literature and the visual arts, late 19th- and early 20th-century movement that was inspired by adaptation of the principles and methods of natural science, especially the Darwinian view of nature, to literature and art. In literature it extended the tradition of realism, aiming at an even more faithful, unselective representation of reality, a veritable “slice of life,” presented without moral judgment. Naturalism differed from realism in its assumption of scientific determinism, which led naturalistic authors to emphasize man's accidental, physiological nature rather than his moral or rational qualities. Individual characters were seen as helpless products of heredity and environment, motivated by strong instinctual drives from within and harassed by social and economic pressures from without. As such, they had little will or responsibility for their fates, and the prognosis for their “cases” was pessimistic at the outset.

Naturalism originated in France and had its direct theoretical basis in the critical approach of Hippolyte Taine (Taine, Hippolyte), who announced in his introduction to Histoire de la littérature anglaise (1863–64; History of English Literature) that “there is a cause for ambition, for courage, for truth, as there is for digestion, for muscular movement, for animal heat. Vice and virtue are products, like vitriol and sugar.” Though the first “scientific” novel was the Goncourt brothers' case history of a servant girl, Germinie Lacerteux (1864), the leading exponent of naturalism was Émile Zola (Zola, Émile), whose essay “Le Roman expérimental” (1880; “The Experimental novel”) became the literary manifesto of the school. According to Zola, the novelist was no longer to be a mere observer, content to record phenomena, but a detached experimenter who subjects his characters and their passions to a series of tests and who works with emotional and social facts as a chemist works with matter. Upon Zola's example the naturalistic style became widespread and affected to varying degrees most of the major writers of the period. Guy de Maupassant's (Maupassant, Guy de) popular story “The Necklace” heralds the introduction of a character who is to be treated like a specimen under a microscope. The early works of Joris-Karl Huysmans, of the German dramatist Gerhart Hauptmann, and of the Portuguese novelist José Maria Eça de Queirós were based on the precepts of naturalism.

The Théâtre Libre (Théâtre-Libre) was founded in Paris in 1887 by André Antoine and the Freie Bühne of Berlin in 1889 by Otto Brahm to present plays dealing with the new themes of naturalism in a naturalistic style with naturalistic staging. A parallel development occurred in the visual arts. Painters (painting), following the lead of the realist painter Gustave Courbet (Courbet, Gustave), were choosing themes from contemporary life. Many of them deserted the studio for the open air, finding subjects among the peasants and tradesmen in the street and capturing them as they found them, unpremeditated and unposed. One result of this approach was that their finished canvases had the freshness and immediacy of sketches. Zola, the spokesman for literary naturalism, was also the first to champion Édouard Manet and the Impressionists.

Despite their claim to complete objectivity, the literary naturalists were handicapped by certain biases inherent in their deterministic theories. Though they faithfully reflected nature, it was always a nature “red in tooth and claw.” Their views on heredity gave them a predilection for simple characters dominated by strong, elemental passions. Their views on the overpowering effects of environment led them to select for subjects the most oppressive environments—the slums or the underworld—and they documented these milieus, often in dreary and sordid detail. The drab palette of Vincent van Gogh's (Gogh, Vincent van) naturalistic painting “The Potato Eaters” (1885; Rijksmuseum, Amsterdam) was the palette of literary naturalism. Finally, they were unable to suppress an element of romantic protest against the social conditions they described.

As a historical movement, naturalism per se was short-lived; but it contributed to art an enrichment of realism, new areas of subject matter, and a largeness and formlessness that was indeed closer to life than to art. Its multiplicity of impressions conveyed the sense of a world in constant flux, inevitably junglelike, because it teemed with interdependent lives.

In American literature, naturalism had a delayed blooming in the work of Hamlin Garland, Stephen Crane, Frank Norris, and Jack London; and it reached its peak in the art of Theodore Dreiser (Dreiser, Theodore). James T. Farrell's (Farrell, James T.) “Studs Lonigan” trilogy (1932–35) is one of the latest expressions of true naturalism.

in philosophy, a theory that relates scientific method to philosophy by affirming that all beings and events in the universe (whatever their inherent character may be) are natural. Consequently, all knowledge of the universe falls within the pale of scientific investigation. Although naturalism denies the existence of truly supernatural realities, it makes allowance for the supernatural, provided that knowledge of it can be had indirectly—that is, that natural objects be influenced by the so-called supernatural entities in a detectable way.

Naturalism presumes that nature is in principle completely knowable. There is in nature a regularity, unity, and wholeness that implies objective laws, without which the pursuit of scientific knowledge would be absurd. Man's endless search for concrete proofs of his beliefs is seen as a confirmation of naturalistic methodology. Naturalists point out that even when one scientific theory is abandoned in favour of another, man does not despair of knowing nature, nor does he repudiate the “natural method” in his search for truth. Theories change; methodology does not.

While naturalism has often been equated with Materialism, it is much broader in scope. Materialism is indeed naturalistic, but the converse is not necessarily true. Strictly speaking, naturalism has no ontological preference; i.e., no bias toward any particular set of categories of reality: dualism and monism, atheism and theism, idealism and materialism are all per se compatible with it. So long as all of reality is natural, no other limitations are imposed. Naturalists have in fact expressed a wide variety of views, even to the point of developing a theistic naturalism.

Only rarely do naturalists give attention to metaphysics (which they deride), and they make no philosophical attempts to establish their position. Naturalists simply assert that nature is reality, the whole of it. There is nothing beyond, nothing “other than,” no “other world” of being.

Naturalism's greatest vogue occurred during the 1930s and '40s, chiefly in the United States among philosophers such as F.J.E. Woodbridge, Morris R. Cohen, John Dewey, Ernest Nagel, and Sidney Hook.