Aristotle, Poetics 1460a26
“Narratives ought to prefer likely events, even if impossible, to improbable possible ones. Stories should not be made from illogical parts: in the best case, they should contain nothing illogical, unless it comes from outside the plot itself as when Oedipus is not aware how Laios died, instead of in the play itself, as when they report the events at Delphi in the Elektra or when the silent man comes from Tegea to Mysia in the Mysians. To say that otherwise the plot would be wrecked is ridiculous—it isn’t right to set up these sorts of events from the beginning.
If a poet does this, and there is a more logical option available, it is strange. Even those illogical events in the Odyssey when Odysseus is put ashore [asleep by the Phaeacians] would have been manifestly intolerable if a lesser poet had created it. In the poem now, Homer softens and erases the strangeness with his other good traits.”
προαιρεῖσθαί τε δεῖ ἀδύνατα εἰκότα μᾶλλον ἢ δυνατὰ ἀπίθανα· τούς τε λόγους μὴ συνίστασθαι ἐκ μερῶν ἀλόγων, ἀλλὰ μάλιστα μὲν μηδὲν ἔχειν ἄλογον, εἰ δὲ μή, ἔξω τοῦ μυθεύματος, ὥσπερ Οἰδίπους τὸ μὴ εἰδέναι πῶς ὁ Λάιος ἀπέθανεν, ἀλλὰ μὴ ἐν τῷ δράματι, ὥσπερ ἐν ᾿Ηλέκτρᾳ οἱ τὰ Πύθια ἀπαγγέλλοντες ἢ ἐν Μυσοῖς ὁ ἄφωνος ἐκ Τεγέας εἰς τὴν Μυσίαν ἥκων. ὥστε τὸ λέγειν ὅτι ἀνῄρητο ἂν ὁ μῦθος γελοῖον· ἐξ ἀρχῆς γὰρ οὐ δεῖ συνίστασθαι τοιούτους. †ἂν δὲ θῇ καὶ φαίνηται εὐλογωτέρως ἐνδέχεσθαι καὶ ἄτοπον† ἐπεὶ καὶ τὰ ἐν ᾿Οδυσσείᾳ ἄλογα τὰ περὶ τὴν ἔκθεσιν ὡς οὐκ ἂν ἦν ἀνεκτὰ δῆλον ἂν γένοιτο, εἰ αὐτὰ φαῦλος ποιητὴς ποιήσειε· νῦν δὲ τοῖς ἄλλοις ἀγαθοῖς ὁ ποιητὴς ἀφανίζει ἡδύνων τὸ ἄτοπον.