Aristotle, Poetics

[1462b] [1] Another point is that it attains its end with greater economy of length. What is concentrated is always more effective than what is spread over a long period; suppose, for example, Sophocles'Oedipuswere to be turned into as many lines as there are in the Iliad . Again, the art of the epic has less unity, as is shown by the fact that any one epic makes several tragedies. The result is that, if the epic poet takes a single plot, either it is set forth so briefly as to seem curtailed, or if it conforms to the limit of length¹ it seems thin and diluted.

In saying that epic has less unity I mean an epic made up of several separate actions. The Iliad has many such parts and so has the Odyssey, and each by itself has a certain magnitude. And yet the composition of these poems is as perfect as can be and each of them is—as far as an epic may be—a representation of a single action. If then tragedy is superior in these respects and also in fulfilling its artistic function—for tragedies and epics should produce not any form of pleasure but the pleasure we have described²—then obviously, since it attains its object better than the epic, the better of the two is tragedy.

This must suffice for our treatment of tragedy and epic, their characteristics, their species, their constituent parts, and their number and attributes; for the causes of success and failure; and for critical problems and their solutions. . . .