Quintilian, and J.S. Watson. Institutes of Oratory.Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book VI Chapter 3.
Quintilian now turns to the place for humor in the work of a rhetorician. This is a means by which the orator revives and enables the judge (Quintilian VI.3.1). Quintilian gives several examples of orators who have used or failed to use humor. It is doubtless a powerful tool. “Though laughter may appear, however, a light thing, as it is often excited by buffoons, mimics, and even fools, it has power perhaps more despotic than anything else, such as can by no means be resisted” (Quintilian VI.3.8).
The ability to use humor is largely a matter of nature, though training and practice are of great value (Quintilian VI.3.12). Humor falls into several categories, which Quintilian identifies as “urbanity” (Quintilian VI.3.17), “grace” or “saltiness” (Quintilian VI.3.18). The particular uses of humor appropriate to a court are intended to incite laughter (Quintilian VI.3.22). Appropriate humor is gentle and uses appropriate language, rather than being crude and insulting (Quintilian VI.3.27). Often that which could be seen as a heavy-handed and severe attack can be more effective through gently and humorously pointing out the same issues (Quintilian VI.3.37).
Quintilian does warn against inappropriate jokes, especially those which are obscure, ambiguous, or have a double meaning (Quintilian VI.3.47). While sometimes effective they are uncertain tactics. He goes on at length to illustrate word plays which may work.
Humor in an argument may be found by observing definitions (Quintilian VI.3.65) or distinctions (Quintilian VI.3.66). It may be used in accusation or refutation (Quintilian VI.3.72). Though the forms of humor are difficult to categorize they remain important and useful.