9. 1. discusses the distinction between Tropes and Figures. This was not clearly made in early theory (and is not made in Ad Herennium) but by Quintilian’s time it was orthodox: Tropes are “unnatural” (i.e. abnormal) uses of words, and Figures are “unnatural” configurations of words or turns of thought. Like the theory of Tropes and Figures in general, the popularity of this distinction and of its underlying concept of “the unnatural” (παρὰ φύσιν) is probably due in the main to Caecilius of Caleacte. Later rhetoricians discuss it: e.g. Alexander Numeniu (3. 9–10 Spengel) and Phoebammon (3. 43–45 Spengel). See Lausberg §§ 600–602, and, for the historical development, R. Granatelli, Rhetorica 12 (1994) 383–425. The theory conspicuously neglects the fact that some Figures (e.g. Anaphora, Antithesis, Chiasmus) reflect the need of oral speech to articulate thoughts in a way readily understood by the hearer (see S. R. Slings, “Figures of Speech and their Lookalikes” in E. J. Bakker (ed.), Grammar and Interpretation (Leiden, 1997) 169–214).
Next (9.1.15–18) follows the distinction between Figures of Speech and Figures of Thought, and then (19–21) some remarks on their usefulness. Quintilian then turns to Cicero, whom he sees as taking a middle course between strict adhesion to the principle of “unnaturalness” and a