E. M. Cope, Commentary on the Rhetoric of Aristotle

τὸ ἑλληνίζειν] Ἑλληνισμός, φράσις ἀδιάπτωτος (Diogenes Laertius, Zeno, VII. 59). τὸ ἑλληνίζειν τριττόν: ἢ τὸ τὴν Ἑλληνικὴν συνήθειαν διασώζειν τῶν ὀνομάτων ἐπὶ πάντων: οἱ πολλοί: ἢ τὸ ἀκριβοῦν τὴν Ἑλληνικὴν φωνήν, καὶ τὴν ὀρθότητα τὴν ἐν τῇ προφορᾶ:ι οἱ γραμματικοί: ἢ τὴν κυριότητα τῶν ὀνομάτων τὴν κατὰ φύσιν προσήκουσαν τοῖς πράγμασιν: οἱ φιλόσοφοι (Schol. ad Plat. p. 70 ap. Gaisford). This takes quite a different view of the meaning of the word to that of Aristotle; in the one case the ‘purity of the Greek’ is shewn in the choice of words, in the other in the connexion of sentences by observance of the idiom of the language. But in fact both of these belong to ‘pure Greek’: and purity is a negative quality of style, consisting in the avoidance of error (φράσις ἀδιάπτωτος, emendata locutio,) in the shape of (1) solecism (Aristotle's view, idiomatic, grammatical, blunders), (2) barbarism; the latter, the use especially of foreign words (whence the name), or any similar impropriety. Atque, ut Latine loquamur, non solum videndum est ut et verba efferamus ea quae nemo iure reprehendat, et ea sic et casibus et temporibus et genere et numero conservemus, &c. Cic. de Orat. III 11.40. In the next section he includes pronunciation. The examples of σολοικισμός, the opposite to ἑλληνισμός, given in de Soph. El. 32, 182 a 13 and 34, are both of them grammatical errors: one who is guilty of either, οὐκ ἀν δοκοίη ἑλληνίζειν. In the same, c. 3, 165 b 20, σολοικίζειν is defined, τῇ λέξει βαρβαρίζειν. [Dem. Or. 45 (κατὰ Στεφάνου ά) § 30, ὑμεῖς δ᾽ ἴσως αὐτὸν ὑπειλήφατε, ὅτι σολοικίζει τῇ φωνῇ, βάρβαρον καὶ εὐκαταφρόνητον εἶναι.]

‘(Pure, correct) Greek is the foundation of style: this falls under five heads or divisions’.