Exposition lays out all the groundwork in a novel that the reader cannot experience directly. Description provides those images and sensations that can be sense or felt, completing a mental picture of the setting and the characters. Dialog helps shape character through verbal interaction, and informs the reader at the same time that it moves action forward. Exposition fills in the gaps left by relying on purely observable description and involves the reader more intimately with the source material. Properly employed exposition addresses history, functionality, or purpose with information the reader needs but cannot witness or easily deduce. It may be presented in dialog, descriptively, or in narrative passages.
Many of the same dangers and rules that surround descriptive passages also apply to expository passages, including information overload from a data dump, the need to anchor the passage with a character, and the Rules of 4. To recap: expository passages should provide only the minimum amount of information necessary for the reader to frame the present and immediate future action, every paragraph should relate the information to a character, and (Rule of 4) a writer may include up to four expositional sentences in a paragraph, one of which must relate the information directly to a character.
Exposition addresses a different type of information that does description, and runs a danger particular to this type of discourse. Where descriptive passages run the risk of turning into hyper-detailed travelouges or catalogs, expositional passages may easily turn into a lecture about the subject matter, and stray from the immediate action. The Rules of 4 help to mediate this risk, but a writer may sometimes decide in the middle of a scene that the reader needs more detail or a more complex concept than can easily be presented using (Rule of 4) only four points of information. At this point, the writer should backtrack in the manuscript and present all the necessary information before the scene begins; this will avoid causing the reader to wander down rabbit trails in the middle of a scene, and potentially lose the flow of action. Exposition presented within a scene should relate closely to the scene; exposition presented outside of a scene’s framework or preparatory to its commencement has more freedom to develop its purpose.
The purpose of exposition once again is to present the reader with necessary information that he cannot witness or easily deduce. This information may be historical, functional, or purposeful. Because the reader does not possess perfect knowledge of the story’s setting, historical information will need to be provided in order to frame the context of a setting or scene. The writer often has far more information about the history of a setting than the reader needs, and should only present those portions that relate to the immediate scene. Because a reader does not possess perfect technical knowledge about how everything in the story functions, it will occassionally become necessary to detail technological workings or the process involved in a procedure. The reader will not wish to have his story interrupted with a technical manual, and will be looking for just enough information to understand what is happening. Purposeful exposition is extremely common, and often takes the form of internal character dialog and thought processes; rather than addressing the what or how of a scene, it speaks to the why. Purposeful exposition enables the reader to understand the instigating circumstances and consequences of an action, but the reader seeks this information only as it relates to the current scene instead of a character’s entire existence.
Presenting exposition often proves problematic; the largest difficulty by far may be avoiding a data dump for the reader’s benefit and working exposition naturally into a scene. Strict exercise of the Rules of 4 will assist with this effort, as will the conscious separation of expository passages from character scenes. Readers need information, but they need it in bite-sized portions, with room to fill in for themselves those portions the writer leaves to their imagination.