In Aristotle's Poetics, he outlines the major principles of tragedy, citing Sophocles' Oedipus as the paragon of the form. Aristotle's reasons are clear: to be the perfect tragedy the play must have a perfect plot. Oedipus follows the classic Aristotelian triangle of rising action, climax, and falling action. The play is full of dramatic irony (the audience knows more than the tragic hero) and verbal irony (the use of sarcasm, understatement, and overstatement).