The most primitive desire underlying the impulse to tell a story is the need to account for things. Primitive stories, often called myths, that account for basic mysteries of existence, such as the creation of the earth or the origins of human life, were once basic explanatory models, much like scientific theories are in modern times. Since their truth could not be tested by checking them against external reality, such stories were judged “true” if they were coherent, that is, if they held together in a plausible and convincing way. In addition to these broad myths, local mythic stories, often called legends, were created to explain some mysterious event unaccounted for by pragmatic criteria or buried in the distant past and thus inaccessible.
The basic motivation underlying both grand cosmic myths and local legends is to create or to represent conceptual ideas in narrative form. When writers begin with the intention of explaining something or illustrating a set of ideas or values, they are most likely to allow the concept to determine the nature of the fiction. Consequently, fables, myths, and allegories are more formal and conventional than realistic stories, for they are governed by the logic of the conceptual ideas that underlie them. The basic difference between fabular narrative and realistic narrative is that the writer of a realistic story is more apt to allow the event or the psychological nature of the characters to determine the structure of the story.
Writers who create realistic stories are usually more concerned with characters who seem to be like real people in the real world, people who have inner thoughts, historical backgrounds, and unpredictable ways. However, writers who construct fables and allegories are so concerned with the idea they wish to illustrate that characters are most often two-dimensional functions of the plot. Angus Fletcher, in a study of allegory, has said that if the reader was to meet an allegorical character in real life, the character would act as if he or she were obsessed, having only one idea in mind, for the allegorical character can be only that emotion, fear, desire, or personality trait that he or she represents.