Quintilian, and J.S. Watson. Institutes of Oratory.Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book VI Chapter 5.
Before moving on to the topics around “disposition,” or ordering arguments, Quintilian discusses sound judgment (Quintilian VI.5.1). While good judgment is generally an innate quality, Quintilian strongly recommends sharpening the skills by observing good examples. He distinguishes between “judgment” and “sagacity” (Quintilian VI.5.3). Judgment works with definitive truth, while sagacity applies to that which is doubtful, for instance, the amount of time or emphasis to dedicate to a part of an argument (Quintilian VI.5.4). As examples of sagacity Quintilian refers to Demosthenes and Cicero.