Epic structure

Epic poetry, like tragedy, must be constructed on dramatic principles. The plot must have a single action — whole and complete, with a beginning, middle, and end — so that the poem produces its proper pleasure as a unified whole. The comparison with history is apt: a historian must treat of a single period, including all that happened to many people in that period; the connections between events are merely temporal and contingent. The poet must treat of a single action, in which every part is organically connected to every other by necessity or probability.

Homer again provides the model. The Iliad does not try to tell the whole Trojan War — it does not begin with the eggs of Leda (from which Helen was born) and end with the sack of Troy or the return of the Greeks. It takes one part of the war — the wrath of Achilles — and uses all other elements as episodes connected necessarily or probably to that action. Most other epic poets fail this test: they write about one man or one era, but the incidents merely follow each other in time; they could be rearranged or removed without the whole being damaged.