CriticaLink | Aristotle: Poetics | Guide to Book VII
While these statements may seem patently obvious, they illustrate the theoretical rigor of Aristotle's approach. A plot cannot begin just anywhere; the opening of tragedy must represent the factors that initiate the chain of events that leads irrevocably to the conclusion.
By "magnitude" Aristotle means something like "proportionality." The audience must be able to grasp the whole of the plot with relative ease. If the play is too short, we lose a sense of development; if it is too long, we lose track of what is happening and our appreciation of the story is impaired.
The rule that the duration of the events represented in a tragedy should encompass not much more than a single daya rule that became hard and fast for some later theorists of tragedy such as the French Neo-Classicistsappears in Aristotle as more of a suggestion, a "rule of thumb." In fact, Aristotle seems to reject any rigid application of time parameters as he concludes this chapter. A play should last, he tells us, as long as it needs to in order to represent a reversal of fortune: a change from good to bad or from bad to good.