Institutio Oratoria

The two first species into which artificial proofs

may be divided are, as I have already said, those which involve a conclusion and those which do not. The former are those which cannot be otherwise and are called τεκμήρια, by the Greeks, because they are indications from which there is no getting away. These however seem to me scarcely to come under the rules of art. For where an indication is irrefutable, there can be no dispute as to facts.