Part XV 

In respect of Character there are four things to be aimed at. First, and most important, it must be good. Now any speech or action that manifests moral purpose of any kind will be expressive of character: the character 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 valor; but valor 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 unraveling 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 the Oedipus of Sophocles. 
Again, since Tragedy is an imitation of persons who are above the common level, the example of good portrait painters should be followed. They, while reproducing the distinctive form of the original, make a likeness which is true to life and yet more beautiful. So too the poet, in representing men who are irascible or indolent, or have other defects of character, should preserve the type and yet ennoble it. In this way Achilles is portrayed by Agathon and Homer. 
These then are rules the poet should observe. Nor should he neglect those appeals to the senses, which, though not among the essentials, are the concomitants of poetry; for here too there is much room for error. But of this enough has been said in our published treatises.
Part XVI 
What Recognition is has been already explained. We will now enumerate its kinds. 
First, the least artistic form, which, from poverty of wit, is most commonly employed- recognition by signs. Of these some are congenital- such as ‘the spear which the earth-born race bear on their bodies,’ or the stars introduced by Carcinus in his Thyestes. Others are acquired after birth; and of these some are bodily marks, as scars; some external tokens, as necklaces, or the little ark in the Tyro by which the discovery is effected. Even these admit of more or less skilful treatment. Thus in the recognition of Odysseus by his scar, the discovery is made in one way by the nurse, in another by the swineherds. The use of tokens for the express purpose of proof- and, indeed, any formal proof with or without tokens- is a less artistic mode of recognition. A better kind is that which comes about by a turn of incident, as in the Bath Scene in the Odyssey. 
Next come the recognitions invented at will by the poet, and on that account wanting in art. For example, Orestes in the Iphigenia reveals the fact that he is Orestes. She, indeed, makes herself known by the letter; but he, by speaking himself, and saying what the poet, not what the plot requires. This, therefore, is nearly allied to the fault above mentioned- for Orestes might as well have brought tokens with him. Another similar instance is the ‘voice of the shuttle’ in the Tereus of Sophocles. 
The third kind depends on memory when the sight of some object awakens a feeling: as in the Cyprians of Dicaeogenes, where the hero breaks into tears on seeing the picture; or again in the Lay of Alcinous, where Odysseus, hearing the minstrel play the lyre, recalls the past and weeps; and hence the recognition. 
The fourth kind is by process of reasoning. Thus in the Choephori: ‘Some one resembling me has come: no one resembles me but Orestes: thereforeOrestes has come.’ Such too is the discovery made by Iphigenia in the play of Polyidus the Sophist. It was a natural reflection for Orestes to make, ‘So I too must die at the altar like my sister.’ So, again, in the Tydeus of Theodectes, the father says, ‘I came to find my son, and I lose my own life.’ So too in the Phineidae: the women, on seeing the place, inferred their fate- ‘Here we are doomed to die, for here we were cast forth.’ Again, there is a composite kind of recognition involving false inference on the part of one of the characters, as in the Odysseus Disguised as a Messenger. A said [that no one else was able to bend the bow; … hence B (the disguised Odysseus) imagined that A would] recognize the bow which, in fact, he had not seen; and to bring about a recognition by this means- the expectation that A would recognize the bow- is false inference. 

But, of all recognitions, the best is that which arises from the incidents themselves, where the startling discovery is made by natural means. Such is that in the Oedipus of Sophocles, and in the Iphigenia; for it was natural that Iphigenia should wish to dispatch a letter. These recognitions alone dispense with the artificial aid of tokens or amulets. Next come the recognitions by process of reasoning.
Poetics By Aristotle