Aristotle suggests that the best kinds of plot are complex plots that arouse fear and pity. He thus concludes that three kinds of plot should be avoided. First, we should avoid plots that show a good man going from happiness to misery, since such events seem more odious than fearful or pitiable. Second, we should avoid plots that show a bad man going from misery to happiness, since this arouses neither pity nor fear and appeals to none of our emotions. Third, we should avoid plots that show a bad man going from happiness to misery, since it will also not arouse the feelings of pity or fear. We feel pity for undeserved misfortune (and a bad man deserves his misfortune), and we feel fear if the person we pity is something like ourselves.
Aristotle concludes that the best kind of plot involves the misfortune of someone who is neither particularly good nor particularly bad and whose downfall does not result from some unpleasantness or vice, but rather from hamartia—an error in judgment. A good plot, then, consists of the following four elements: (1) It must focus around one single issue; (2) the hero must go from fortune to misfortune, rather than vice versa; (3) the misfortune must result from hamartia; and (4) the hero should be at least of intermediate worth, and if not, he must be better—never worse—than the average person. This explains why tragedies tend to focus around a few families (there are many tragedies about the families of Oedipus and Orestes among others): they must be upstanding families that suffer great misfortune from an error in judgment rather than a vice. Only second-rate plots that pander too much to public taste focus on a double issue where the good fare well and the bad fare poorly.
Pity and fear—which Aristotle calls the "pleasures" of tragedy—are better if they result from the plot itself rather than the spectacle. A story like that of Oedipus should be able to arouse pity and fear even if it is told without any acting at all. The poet who relies on spectacle is relying on outside help, whereas the poet who relies only on his own plot is fully responsible for his creation.
We feel pity most when friends or family harm one another, rather than when unpleasantness takes place between enemies or those who are indifferent to one another. The deed may be done knowingly—as when Medea kills her children—or unknowingly—as when Oedipus kills his father. A third alternative is that one character plans to kill another, but then discovers the family connection between them in time to refrain from the killing.
Thus, the deed can either be done or not done, and it can take place in either ignorance or knowledge. Aristotle suggests that the best kind of plot is of the third alternative, where anagnorisis allows a harmful deed to be avoided. The second best case is where the deed is done in ignorance. And the third best is the case where the deed is done with full knowledge. Worst is the case where there is full knowledge throughout, and the premeditated deed is only refrained from at the moment of action. This scenario is not tragic because of the absence of suffering, and it is odious besides. Still, Aristotle acknowledges that it has been used to good effect, as with the case of Haemon and Creon in Antigone .
The Greek word hamartia translates pretty directly as "error" or "shortcoming" without any necessary overtones of guilt or moral failure. Our modern conception of tragedy and the "tragic flaw" of the hero usually involves the concept of hubris, or overweening pride, that leads to disaster. Macbeth, for instance, has the arrogance to think he can overstep the laws of God and state and ultimately pays dearly for this arrogance. Macbeth is a tragic hero with a clear tragic flaw: his downfall results from a moral failing and can be seen as divine retribution proportional to his guilt. But Macbeth also contains heavy Christian overtones that would of course be found nowhere in Greek tragedy. An understanding of Aristotle's concept of hamartia—and indeed an understanding of Greek tragedy in general—relies on an understanding of the ethics and cosmology of the ancient Greeks.
The ethics the modern Western world has inherited from Christianity is an ethics of obligation. In this system, there are certain moral laws, and we are obligated to obey them. A failure to obey these laws represents an unwillingness on our part. If we go against the moral law, we are guilty of breaking that law. This conception of guilt draws on an ethical system wherein morality is something that can be disobeyed or resisted.
Greek ethics are based more on the notion of virtue than obligation. The Greek conception of reality is closely tied up to the concepts of goodness and harmony. This idea is clearly expressed in Plato's theory of Forms: the real world is made up of perfect, unchanging Forms, and it is our duty to approximate this reality as best we can. Virtue, for the Greeks, is a matter of attaining our real nature and of finding our true form. Thus, moral failure is not a matter of guilty recalcitrance, but simply a matter of error, of shortcoming, or of being unable for whatever reason to attain our true nature.
Hamartia, then, represents the Greek, and not the Christian, conception of moral failure. Greek heroes are not bad people—Aristotle explicitly states that they cannot be bad people—but are simply good people who fall short in some important respect. Tragedy is less a matter of showing how bad people are punished for their crimes, and is more a matter of showing how ignorance and error can have disastrous effects. The action is tragic precisely because we are all ignorant to some degree, all flawed, and we may all suffer deeply for these errors. This is a cold, hard fact of nature, and not a matter of justice and retribution.
In these sections, Aristotle is much less of an observer and much more of a legislator. He is no longer simply stating how tragedies tend to play themselves out but is now putting forward arguments as to what makes the best tragic plot. He is explicitly asking how we can maximize the feelings of pity and fear, which he calls "tragic pleasure." That he should refer to our pity and fear as "pleasure" is further evidence that he does not mean the kind of pity and fear we might experience were the events real.
However, Aristotle does seem to treat this kind of pity and fear as the goal of a good tragedy, which would contradict the commentary on Chapter 6 (which suggested that tragedians aim at more than just emotional therapy). We can perhaps answer this conundrum by treating pity and fear as a necessary means to some other end. Surely, Aristotle does not think the value of tragedy lies simply in its emotional effect but thinks rather that it lies in what these emotional effects can in turn provoke within us. This ultimate end is naturally harder to articulate, but it has something to do with a greater sense of awareness—of our shortcomings, of our fate, and of our behavior, etc. Presumably, this added awareness helps us overcome our ignorance and other shortcomings; in short, tragedy can help us with our own hamartia.
The question Aristotle focuses on, however, is how fear and pity are most effectively aroused? He suggests that the tragic hero ought to be neither overwhelmingly good nor overwhelmingly bad, but rather intermediate, much like us. We should be able to see in the hero a better version of ourselves. Our pity and fear will be aroused by the realization that if a better person than us can be made to suffer for his or her shortcomings, then we, too, may suffer for ours.
We find a seeming inconsistency in Aristotle's commendation of the best kind of plot being that where disaster is narrowly averted by ignorance turning into knowledge. Aristotle also seems to suggest that tragedy must take the hero from fortune to misfortune. Perhaps by the moment of anagnorisis the hero has already suffered misfortune enough.