Greek philosopher, Aristotle, wrote an analysis of theater called Poetics. Boal interprets Aristotle's Poetics as describing a theater of coercion, which is meant to prevent rebellion and promote the status quo. Boal believed that Aristotle's worldview finds virtue in temperance, and thus, considers extremes to be vices.
Aristotle's focus in Poetics is tragedy, and in his tragedy, the hero is always a high-ranking, virtuous man, who has one single flaw. Boal's believes that the virtues of the man reflect the qualities that are desired by the existing oppressive society, and that the flaw is a rebellious quality that exists in all people to some extent. In this way, the audience empathizes with the hero, giving over their free will to his character.
Theatre of the Oppressed