Quintilian, and J.S. Watson. Institutes of Oratory. Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book 7 Chapter 4.
In chapter four of book seven of his Institutes of Oratory, Quintilian discusses arguments of quality. What is the quality of the event being considered in a case (Quintilian VII.4.1)? Arguments of quality are especially frequent in deliberative discourse (Quintilian VII.4.2), but are also common in demonstrative speeches and in the penalty phase of trials (Quintilian VII.4.3). The argument justifying actions may well be categorized under arguments of quality (Quintilian VII.4.4). Quintilian gives numerous examples.
In some situations the orator may try “to transfer the charge, if we find it possible, on another party” (Quintilian VII.4.13). The defendant in a case may have acted through coercion, misinformation, or some other motivation which would make him not responsible, or at least less responsible. “Should these modes of defense fail us, there remains excuse, founded either on ignorance or on necessity” (Quintilian VII.4.13). Some, however, suggest that excuse is a matter of quantity rather than quality of a deed (Quintilian VII.4.15). Quintilian considers that quantity is tied to the quality of a deed and should be assessed in the same terms (Quintilian VII.4.16).
It is also certainly possible, though a last resort, to engage in deprecation. Here the orator condemns the opponent or the charge itself (Quintilian VII.4.17). “It sometimes derives its greatest efficacy from the character of the accused himself, if it appear, from his previous life, that there are these three kinds of merit in him: that he has lived innocently, that he has been serviceable to others, and that he affords expectation that he will conduct himself blamelessly for the future…” (Quintilian VII.4.18).
Deprecation is closely related to questions of equity, evaluation of whether or not a situation is fair (Quintilian VII.4.25-26). Quintilian closes the chapter with many examples of cases in which equity is an important factor.