'That language is elevated and remote from the vulgar idiom which employs unusual words: by unusual, I mean foreign, metaphorical, extended—all, in short, that are not common words. Yet, should a poet compose his Diction entirely of such words, the result would be either an enigma or a barbarous jargon: an enigma if composed of metaphors, a barbarous jargon if composed of foreign words. For the essence of an enigma consists in putting together things apparently inconsistent and impossible, and at the same time saying nothing but what is true. Now this cannot be effected by the mere arrangement of words; by the metaphorical use of them it may.'
On Life and Poetry of Homer
, wrongly ascribed to Plutarch, Bk. I. § 16.
Poetics
, II. § 26.
'A judicious intermixture is requisite ... It is without reason, therefore, that some critics have censured these modes of speech, and ridiculed the poet for the use of them; as old Euclid did, objecting that versification would be an easy business, if it were permitted to lengthen words at pleasure, and then giving a burlesque example of that sort of diction... In the employment of all the species of unusual words, moderation is necessary: for metaphors, foreign words, or any of the others improperly used, and with a design to be ridiculous, would produce the same effect. But how great a difference is made by a proper and temperate use of such words may be seen in heroic verse. Let any one put common words in the place of the metaphorical, the foreign, and others of the same kind, and he will be convinced of the truth of what I say.'