Decorum, from the Latin word meaning "right" or "proper," is a principle in classical rhetoric, poetry, and theatrical theory that refers to whether a style is suitable for a particular subject in theater. The concept of decorum also includes rules about how people should behave in certain situations according to social expectations.

In rhetoric and poetry

In classical rhetoric and poetic theory, decorum refers to how well the style of writing or speaking matches the topic. Aristotle, in his work Poetics, and Horace, in Ars Poetica, both emphasized the importance of using a style that fits the subject, such as epic, tragedy, or comedy. Horace explained that a comic subject should not be written in a tragic style, and a serious event, like the banquet of Thyestes, should not be described in a casual or humorous tone. Each style, he said, should be used only for the purpose it is meant for.

During the Hellenistic and Latin periods, writers divided style into three categories: grand style, middle style, and low (or plain) style. Each style had its own vocabulary and tone, and writers followed rules about which words were suitable for each. This idea was discussed in the Rhetorica ad Herennium, a work that was modeled after Virgil’s three-part literary career: Bucolics, Georgics, and Aeneid. Ancient, medieval, and Renaissance theorists often linked each style to a specific genre: epic (high style), didactic (middle style), and pastoral (plain style). In the Middle Ages, this system was called "Virgil’s wheel."

For those who strictly followed style rules, mixing different styles in a single work was considered wrong. Epic poetry, in particular, was expected to use only the high style consistently. However, classical epics, like those by Virgil or Homer, often included scenes with humor or romance, showing that style diversity was common in early works. Poetry, more than other forms, often used words and phrases that were not used in everyday speech, known as poetic diction.

With the rise of Christianity, ideas about decorum changed. While religious topics were sometimes treated humorously in medieval drama, religious institutions carefully controlled how sacred subjects were presented in more permanent art forms, requiring a consistent "high style." By the Renaissance, combining classical mythology with Christian themes or mixing religious subjects with lively scenes in art was also considered part of decorum. The Catholic Council of Trent specifically banned "indecorous" elements in religious art.

As time passed, some people began to see decorum as restrictive. Writers in the Modernist movement challenged these ideas, leading readers to no longer expect strict adherence to decorum. This shift made the humor in mock-heroic writing, burlesque, and even the use of bathos less effective for twentieth-century readers.

In theatre

During the Renaissance and the time after the Renaissance in Europe, people discussed what was proper for plays on stage. They looked to ancient examples and the ideas of Aristotle and Horace, including the "Three Unities." These rules suggested that some events were better described in stories rather than shown on stage. In Horace's Ars Poetica, he advised playwrights to avoid scenes that might shock or confuse the audience, such as those showing extreme cruelty or impossible events. He wrote that certain scenes, like Medea harming her children, Atreus cooking human flesh, or Procne changing into a bird, should not be performed on stage but instead described by a narrator.

In Renaissance Italy, debates about what was proper in plays were influenced by Sperone Speroni’s play Canace, which included a story about a brother and sister in an improper relationship, and Giovanni Battista Giraldi’s play Orbecche, which showed violent revenge and the killing of a parent. In 17th-century France, the idea of proper behavior (les bienséances) was a major part of French classicism, which shaped theater, novels, and visual art.

Social decorum

Social decorum refers to the proper ways people should behave in society. It connects to ideas like courtesy, respect, and good manners.

The rules of social decorum, which focus on keeping things proper on the outside, were clearly explained by Lord Chesterfield. He was trying to translate the French word les moeurs, which means "customs" or "ways of life." He said, "Manners are too little, morals are too much," showing that decorum is about behavior, not strict rules. The word decorum has been used since the 16th century to describe the limits of proper behavior in certain situations. This idea appears in books like The Scholemaster by Roger Ascham (1570) and in a speech by a character named Malvolio in the play Twelfth Night, who says, "Have you no wit, manners, nor honesty…?"

In courtrooms, decorum means following rules about what kinds of arguments are allowed. This was an important topic during the O.J. Simpson trial.

At Model United Nations conferences, the chairperson might say, "Decorum delegates!" if participants are not following the rules for speaking or acting. This usually happens when someone talks out of turn or causes disruptions.