The Bedford Glossary of Critical and Literary Terms - Ross Murfin 2018
Decorum: (1) Generally, propriety of conduct in accordance with societal conventions. (2) In rhetoric, propriety in argument matching subject and words. (3) In literature, propriety of the elements in a literary work (particularly poetry) such that style, character, setting, subject, action, language, and situation are compatible and fitting. The idea of literary decorum dates back to classical times; in the Poetics (c. 330 B.C.), for instance, the Greek philosopher Aristotle asserted the dual importance of choosing the appropriate and avoiding the inconsistent in areas such as characterization and genre, and in Ars poetica (Art of Poetry) (c. 20 B.C.) the Roman poet Horace stressed the need for appropriateness and consistency among elements such as characterization, language, subject, and style to maintain a work’s unity. Literary decorum was also championed by Renaissance and neoclassical critics, who drew heavily on their classical predecessors and emphasized the importance both of choosing an appropriate style and of using “correct” language. Notably, while decorum has remained a locus of critical attention since classical times, many writers have adapted or even disregarded the prevailing decorum of their time to suit their particular needs and goals.
EXAMPLE: Literary decorum dictates that a young chimney sweeper depicted in a Victorian novel should not speak in the elevated, high-mannered, and grammatically precise style of an Oxford don. In Oliver Twist (1837), Charles Dickens deliberately broke the rules of decorum by giving the workhouse orphan Oliver Twist the speech of a young gentleman.