Quintilian, and J.S. Watson. Institutes of Oratory. Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book 9 Chapter 1.
Quintilian has previously addressed the idea of tropes. Now he speaks of “figures,” which are often confused with tropes. They are very similar and are used in much the same way, making confusion natural (Quintilian IX.1.3). “A trope...is an expression turned from its natural and principal signification to another.” “A figure...is a form of speech differing from the common and ordinary mode of expression” (Quintilian IX.1.4). Quintilian then summarizes the tropes about which he wrote previously. He then shows that figures use natural words in their normal order (Quintilian IX.1.7). The idea of a figure of speech used here is “that which deviates, by poetical or oratorical phraseology, from the simple and ordinary modes of speaking” (Quintilian IX.1.13). Most authors will distinguish between figures of thought and figures of speech (Quintilian IX.1.18). The figures of thought are the processes used to approach a topic. The order of ideas or the way one proves a point is a figure of thought (Quintilian IX.1.21). Quintilian continues with extensive quotes from Cicero De Oratore book 3 (Quintilian IX.1.21). Cicero lists many ways in which speech can be varied to accomplish a purpose.