According to Aristotle, tragedy has six main elements: plot, character, diction, thought, spectacle (scenic effect), and song (music), of which the first two are primary. Most of the Poetics is devoted to analysis of the scope and proper use of these elements, with illustrative examples selected from many tragic dramas, especially those of Sophocles, although Aeschylus, Euripides, and some playwrights whose works no longer survive are also cited.

Several of Aristotle's main points are of great value for an understanding of Greek tragic drama. Particularly significant is his statement that the plot is the most important element of tragedy:

Tragedy is an imitation, not of men, but of action and life, of happiness and misery. And life consists of action, and its end is a mode of activity, not a quality. Now character determines men's qualities, but it is their action that makes them happy or wretched. The purpose of action in the tragedy, therefore, is not the representation of character: character comes in as contributing to the action. Hence the incidents and the plot are the end of the tragedy; and the end is the chief thing of all. Without action there cannot be a tragedy; there may be one without character. . . . The plot, then, is the first principle, and, as it were, the soul of a tragedy: character holds the second place.

Aristotle goes on to discuss the structure of the ideal tragic plot and spends several chapters on its requirements. He says that the plot must be a complete whole — with a definite beginning, middle, and end — and its length should be such that the spectators can comprehend without difficulty both its separate parts and its overall unity. Moreover, the plot requires a single central theme in which all the elements are logically related to demonstrate the change in the protagonist's fortunes, with emphasis on the dramatic causation and probability of the events.

Aristotle has relatively less to say about