Institutio Oratoria

I now pass to things: of these actions are the most nearly connected with persons and must therefore be treated first. In regard to every action the question arises either Why or Where or When or How or By what means the action is performed.

Consequently arguments are drawn from the causes of past or future actions. The matter of these causes, by some called ὕλη, by others δύναμις, falls into two genera, which are each divided into four species. For the motive for any action is as a rule concerned with the acquisition, increase, preservation and use of things that are good or with the avoidance, diminution, endurance of things that are evil or with escape there from. All these considerations carry great weight in deliberative oratory as well.

But right actions have right motives, while evil actions are the result of false opinions, which originate in the things which men believe to be good or evil. Hence spring errors and evil passions such as anger, hatred, envy, desire, hope, ambition, audacity, fear and others of a similar kind. To these accidental circumstances may often be added, such as drunkenness or ignorance, which serve sometimes to excuse and sometimes to prove a charge, as for instance when a man is said to have killed one person while lying in wait for another. Further,

motives are often discussed not merely to convict the accused of the offence with which he is charged, but also to defend him when he contends

Questions of definition are also at times intimately connected with motives. Is a man a tyrannicide if he kills a tyrant by whom he has been detected in the act of adultery? Or is lie guilty of sacrilege who tore down arms dedicated in a temple to enable him to drive the enemy from the city?