Digression in literature is a section of a composition or speech that is an intentional change of subject. In Classical rhetoric, the digression was a regular part of any oration or composition. After setting out the topic of a work and establishing the need for attention to be given, the speaker or author would digress to a seemingly disconnected subject before returning to a development of the composition's theme, a proof of its validity, and a conclusion. This use of the digression is still noticeable in many sermons: after the topic, the speaker will introduce a "story" that seems to be unrelated, return to the subject, and then reveal that the story illustrates the speaker's point.
In literature, the digression (not to be confused with subplot) was a substantial part of satiric works of the 18th century. Works such as Jonathan Swift's A Tale of a Tub and Laurence Sterne's Tristram Shandy made digressiveness itself a part of the satire. This use of digression as satire later showed up in Thomas Carlysle's work. The digression was also used for non-satiric purposes in fiction. In Henry Fielding's Tom Jones, the author has numerous asides and digressive statements that are a side-fiction, and this sort of digression within chapters shows up later in the work of Charles Dickens, William Makepeace Thackeray, and others.
