External forces in a tragedy include fate, fortune, the gods, and circumstances. The internal forces include "error or frailty." The Greek term he uses in The Poetics is harmartia, translated as "tragic flaw."
The final elements are the reversal of action and the growth of understanding, or self-knowledge.
Aristotle calls the reversal of action or intention the peripete : the instant when there is a "change by which the action veers around to its opposite." The moment of comprehension is the recognition (anagnorisis).
This recognition means that the protagonist canes to understand his place in the scheme of things - a paraphrase of Aristotle.
