Institutio Oratoria

Cause, under which heading come a large number of disputes, whenever a fact is not denied, but the defence pleads that the act was just and reasonable. τρόπος or manner, which is involved when a thing is said to have been done in one way when it might have been done in another: under this category come cases of such as that of the adulterer who is scourged with thongs or starved to death. [*]( An adulterer caught flagrante delicto might be killed by the husband or beaten. But to starve him to death in cold blood would be illegal. ) Opportunity for action, the meaning of which is too obvious to need explanation or illustration: the Greeks however call it ἔργων ἀφορμαί

These authorities like Aristotle hold that no question can arise which does not come under one of these heads. Some subtract two of them, namely number and opportunity, and substitute for what I have called action, things, or in Greek πράγματα. I have thought it sufficient to notice these doctrines, for fear someone might complain of their omission. Still I do not consider that bases are sufficiently determined by these categories, nor that the latter cover every possible kind of topic, as will be clear to any that read carefully what I have to say on both points. For there will be found to be many topics that are not covered by these categories.