To realize the difference one should take
an epic verse and see how it reads when the normal words
are introduced. The same should be done too with the
strange word, the metaphor, and the rest; for one has
only to put the ordinary words in their place to see the
truth of what we are saying. The same iambic, for instance,
is found in Aeschylus and Euripides, and as it stands in
the former it is a poor line; whereas Euripides, by the
change of a single word, the substitution of a strange for
what is by usage the ordinary word, has made it seem a fine
one. Aeschylus having said in his Philoctetes:
φαγέδαινα ἥ μου σάρκας ἐσθίει ποδός,
Euripides has merely altered the
ἐσθίει here into
θοινᾶται.
Or suppose
νῦν δέ μ᾽ ἐὼν ὀλίγος τε καὶ οὐτιδανὸς καὶ ἀεικής
to be altered by the substitution of the ordinary words into
νῦν δέ μ᾽ ἐὼν μικρός τε καὶ ἀσθενικὸς καὶ ἀειδής.
Or the line
δίφρον ἀεικέλιον καταθεὶς ὀλίγην τε τράπεζαν
into
δίφρον μοχθηρὸν καταθεὶς μικράν τε τράπεζαν.
Or
ἠιόνες βοόωσιν
into
ἠιόνες κράζουσιν.