Bearing in mind that Greek drama, comedy and tragedy, was written in poetic verse and not in prose, it make sense that Aristotle's treatise Poetics is a critical work defining tragedy. There are many points in Poetics but Aristotle early on discusses the concept of mimesis, the belief and theory that poetry, in particular tragedy, is the "imitation of an action" that accords to the "law of probability or necessity."

This means that according to Aristotle's poetics--theory of the role, function, structure, and nature of poetry--tragedy records what may be seen in life, as history does, but then it goes beyond history and surmises on the "law of probability and necessity" what may happen as a result of cause-and-effect chains of events and reactions. The audience can see in dramatic poetry (tragedy) the reasonable end result of errors based on flaws in inner character traits or mistakes in judgment, which produces a feelings of pity and fear of consequences for the character.