Institutio Oratoria

the mark of a shrewd debater to perceive what remarks impress the judge and what he rejects: this may often be detected from his looks, and sometimes from some action or utterance. Arguments which help us must be pressed home, while it will be wise to withdraw as gently as possible from such as are of no service. We may take a lesson from doctors who continue or cease to administer remedies according as they note that they are received or rejected by the stomach. Sometimes,

if we find difficulty in developing our point, it is desirable to raise another question and to divert the attention of the judge to it if this be feasible. For what can you do, if you are unable to answer an argument, save invent another to which your opponent can give no answer?