The reversal of one condition of circumstances to its opposite is referred to as peripeteia. Some story event causes a reversal, such that the hero, who believed he was in good shape, discovers that all is lost, or vice versa. The transition from ignorance to knowledge is referred to as anagnorisis. In the Iliad, this moment occurs when Agamemnon realizes that Achilles is fighting against both Troy and his own army. Anagnorisis and peripeteia are important elements in any narrative poem, play, or novel. They show the audience or reader how our main character reacts to circumstances beyond their control. Anagnorisis is when the main character realizes something important about themselves or their situation, while peripeteia is the reversal of this realization - it shows us how our character deals with this new information. In classical drama, anagnorisis and peripeteia were used by poets to increase tension before the action of their plays, because their audiences would expect something dramatic to happen at these points. For example, in Aeschylus' Oresteian trilogy, the anagnorisis is when Clytemnestra learns that her husband has been murdered, and she goes insane with grief. Peripeteia then follows, as she is forced to choose between saving her children from death at the hands of Orestes or staying loyal to her husband's memory.