since tragedy represents not only a complete action but also incidents that cause fear and pity, and this happens most of all when the incidents are unexpected and yet one is a consequence of the other. [Note]
For in that way the incidents will cause more amazement than if they happened mechanically and accidentally, since the most amazing accidental occurrences are those which seem to have been providential, for instance when the statue of Mitys at Argos killed the man who caused Mitys's death by falling on him at a festival. Such events do not seem to be mere accidents.
So such plots as these must necessarily be the best.
Some plots are "simple" and some "complex," as indeed the actions represented by the plots are obviously such.
By a simple action I mean one that is single and continuous in the sense of our definition above, [Note] wherein the change of fortune occurs without "reversal" or "discovery";
by a complex action I mean one wherein the change coincides with a "discovery" or "reversal" or both.
These should result from the actual structure of the plot in such a way that what has already happened makes the result inevitable or probable;
for there is indeed a vast difference between what happens propter hoc and post hoc.
A "reversal" is a change of the situation into the opposite, as described above, [Note] this change being, moreover, as we are saying, probable or inevitable—
like the man in the Oedipus who came to cheer Oedipus and rid him of his anxiety about his mother by revealing his parentage and changed the whole situation. [Note] In the Lynceus, too, there is the man led off to execution and
Danaus following to kill him, and the result of what had already happened was that the latter was killed and the former escaped. [Note]
A "discovery," as the term itself implies, is a change from ignorance to knowledge, producing either friendship or hatred in those who are destined for good fortune or ill.
A discovery is most effective when it coincides with reversals, such as that involved by the discovery in the Oedipus.
There are also other forms of discovery, for what we have described may in a sense occur in relation to inanimate and trivial objects, or one may discover whether some one has done something or not.
But the discovery which is most essentially part of the plot and part of the action is of the kind described above, for such a discovery and reversal of fortune will involve either pity or fear,