Poetics (Samuel H. Butcher Translation) Unit Six, Chapter 13 & 14
As the sequel to what has already been said, we must proceed to consider what the poet should aim at, and what he should avoid, in constructing his plots; and by what means the specific effect of Tragedy will be produced.
A perfect tragedy should, as we have seen, be arranged not on the simple but on the complex plan. It should, moreover, imitate actions which excite pity and fear, this being the distinctive mark of tragic imitation. It follows plainly, in the first place, that the change, of fortune presented must not be the spectacle of a virtuous man brought from prosperity to adversity, for this moves neither pity nor fear; it merely shocks us. Nor, again, that of a bad man passing from adversity to prosperity, for nothing can be more alien to the spirit of Tragedy; it possesses no single tragic quality; it neither satisfies the moral sense nor calls forth pity or fear. Nor, again, should the downfall of the utter villain be exhibited. A plot of this kind would, doubtless, satisfy the moral sense, but it would inspire neither pity nor fear; for pity is aroused by unmerited misfortune, fear by the misfortune of a man like ourselves. Such an event, therefore, will be neither pitiful nor terrible. There remains, then, the character between these two extremes -- that of a man who is not eminently good and just, yet whose misfortune is brought about not by vice or depravity, but by some error or frailty, some hamartia. He must be one who is highly renowned and prosperous -- a personage like Oedipus, Thyestes, or other illustrious men of such families.
A well-constructed plot should, therefore, be single in its issue, rather than double as some maintain. The change of fortune should be not from bad to good, but, reversely, from good to bad. It should come about as the result not of vice, but of some great error or frailty, in a character either such as we have described, or better rather than worse....
XIV [Pity and Fear]
Fear and pity may be aroused by spectacular means; but they may also result from the inner structure of the piece, which is the better way, and indicates a superior poet. For the plot ought to be so constructed that, even without the aid of the eye, he who hears the tale told will thrill with horror and melt to pity at what takes place....