will be good if the purpose is good. This rule is relative to each class.
Even a woman may be good, and also a slave; though the woman may be said
to be an inferior being, and the slave quite worthless. The second thing
to aim at is propriety. There is a type of manly valour; but valour in a
woman, or unscrupulous cleverness, is inappropriate. Thirdly, character
must be true to life: for this is a distinct thing from goodness and
propriety, as here described. The fourth point is consistency: for though
the subject of the imitation, who suggested the type, be inconsistent,
still he must be consistently inconsistent. As an example of motiveless
degradation of character, we have Menelaus in the Orestes: of character
indecorous and inappropriate, the lament of Odysseus in the Scylla, and
the speech of Melanippe: of inconsistency, the Iphigenia at Aulis,--for
Iphigenia the suppliant in no way resembles her later self.

As in the structure of the plot, so too in the portraiture of character,
the poet should always aim either at the necessary or the probable. Thus
a person of a given character should speak or act in a given way, by the
rule either of necessity or of probability; just as this event should
follow that by necessary or probable sequence. It is therefore evident
that the unravelling of the plot, no less than the complication, must
arise out of the plot itself, it must not be brought about by the 'Deus
ex Machina'--as in the Medea, or in the Return of the Greeks in the
Iliad. The 'Deus ex Machina' should be employed only for events external
to the drama,--for antecedent or subsequent events, which lie beyond the
range of human knowledge, and which require to be reported or foretold;
for to the gods we ascribe the power of seeing all things. Within the
action there must be nothing irrational. If the irrational cannot be
excluded, it should be outside the scope of the tragedy. Such is the
irrational element in the Oedipus of Sophocles.