Чем отличается реализм от натурализма?

Реализм - (лат. вещественный, действительный) – направление в литературе и искусстве, ставящее целью правдивое воспроизведение действительности в её типических чертах.
Натурализм - направление в литературе и искусстве последней трети 19 в., стремящееся к внешне точному, фактографическому отображению действительности.

naturalism, 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.