Institutio Oratoria

As regards arguments, they may be found either in the questions raised by the case, which may be considered by themselves quite apart from any connexion with individual

things or persons, or in the case itself, when anything is discovered in it which cannot be arrived at by the light of common reason, but is peculiar to the subject on which judgment has to be given. Further, all proofs fall into three classes, necessary, credible, and not impossible.