Aristotle believes in teleology, a metaphysical position according to which everything has a function or end to fulfill. Every kind of poetic imitation has its own assigned function, says Aristotle. The function of a tragedy is to succeed through the representation of an action that is serious, complete and of certain magnitude, in arousing pity and fear in such a way as to accomplish a purgation or Catharsis of such emotions. So tragedy works in a two folds ways 1, first exciting the emotions of fear and pity and 2, then abating them, thereby effecting an emotional cure.
So, Catharsis or purgation, the most debate arousing word in entire Poetics, depends on the emotions coming from the combination of pity and fear. By pity Aristotle means the sympathy we feel for the undeserving sufferer. We pity one who is suffering and to pity we must participate to some extent in his suffering. But we feel pity for one who suffers more than he should. We feel pity for Oedipus, when we see him suffering from undeserved misfortune. We feel pity for Agamemnon hearing his death-cry.
Agamemnon is not wholly responsible for such kind of suffering. Another essential part of suffering is fear which we feel for someone just like ourselves. It is closely connected with pity. We pity others, while we fear for ourselves, if we are placed in these circumstances. We have a sympathetic emotion of fear for one who is similar to us. When we see Oedipus on the stage is suffering from untold sufferings. We realize our kinship or identity with him. And the effect of tragedy depends on this inward similarity between the hero and the spectator. The hero is as much a human being as any of us. Imaginatively, we feel that we too may meet such a fate, and we recoil.
According to Aristotle there are two ways in which fear and pity can be aroused in the audience. Fear and pity may be excited in the audience by means spectacle. But they can also take their rise from very structure of the action and this is the bitter way and indicates the superior art. In fact, the plot should be so constructed that even without the use of his eyes, the listener, who hears the late, will be thrill with horror and melt to pity at what happens in the story. This is the impression we should receive from listening to the story of Oedipus. But to produce this effect by means of stage-spectacle is less artistic and those who employ spectacle to produce an effect, not of fear, but of something merely monstrous, are ignorant of the purpose of tragedy. The purpose of tragedy is to give pleasure which comes from pity and fear through imitation.
Fear and pity can also take their rise from the very structure of the plot. And in order to produce such situations the dramatists should choose those horror-deeds that take place between persons who are near and dear to each other. A brother killing or intending to kill a brother, for example- Polyneices killing of Eteodes in Antigone, son killing his father, as Oedipus did, a mother killing her son as Medea did or son killing his mother or any other deeds of same kinds the tragic dramatist must choose. We see that the most of the situations suitable to tragedy are supplied by a number of well- known legends of these well-known families, such as that of Clytemnestra having been killed by Orestes or Eriphyle by Alemaeon.
But the duty of a dramatist is to use these elements effectively. He should use his inventive faculty. Aristotle has suggested four possible ways in which these horror-deeds can be committed.
1) The deed may be done by characters acting consciously and in full knowledge of the facts for example Euripides made Medea kill her children.
2) Or they may do it without realizing the horror of the deeds until later, when they discover the truth, this is what Sophocles did with Oedipus.
3) A third alternative is for someone who is about to do a terrible deed in ignorance of the relationship and to discover the truth before he does it.
4) There is still another way which is least acceptable. In this situation someone in possession of the facts is on the point of acting but fails to do so. Such a situation is shocking without being tragic, because no disaster occurs. Hence nobody is allowed to behave like this, as when Haemon fails to kill Creon in the Antigone.
It is better that the character should act in ignorance and only learn the truth afterwards for there is nothing in this to outrage. Our feelings and the revelation comes as a surprise. However, the best method is one in which the character is about to do an act of ignorance but discovers the truth before he does, when for example in the Cresphontes Merope intends to kill her son, but recognizes him and does not do so, or when the same thing happens with brother and sister in Iphigena in Tauris or when in the Helle, the son recognizes his mother when he is just about to betray her.
There is a controversy over the fact that which way is the best, the first one or the second one. If we keep in mind the arguments put forward by Aristotle, then it seems to us that the situation in which character does a thing in complete ignorance and later discovers the truth is the best way. But the contradiction arises from the very language Aristotle has used.