Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
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
Again there are four forms of proof. First, we may argue that, because one thing is, another thing is not; as It is day and therefore not night. Secondly, we may argue that, because one thing is, another thing is; as The sun is risen, thereit is day. Thirdly, it may be argued that because one thing is not, another thing is; as It is not night, therefore it is day. Finally, it may be argued that, because one thing is not, another thing is not; as He is not a reasoning being, therefore he is not a man. These general remarks will suffice by way of introduction and I will now proceed to details.
Every artificial proof consists either of indications, arguments or examples. I am well aware that many consider indications to form part of the arguments. My reasons for distinguishing them are twofold. In the first place indications as a rule come under the head of inartificial proofs: for a bloodstained garment, a shriek, a dark blotch and the like are all evidence analogous to documentary or oral evidence and rumours; they are not discovered by the orator, but are given him with the case itself.
My second reason was that indications, if indubitable, are not arguments, since they leave no room for question, while arguments are only possible in controversial matters. If on the other hand they are doubtful, they are not arguments, but require arguments to support them.
The two first species into which artificial proofs
This happens whenever there can be no doubt that something is being or has been done, or when it is impossible for it to be or have been done. In such cases there can be no dispute as to the fact. This kind of proof may be considered in connexion with past, present or future time.
For example, a woman who is delivered of a child must have had intercourse with a man, and the reference is to the past. When there is a high wind at sea, there must be waves, and the reference is to the present. When a man has received a wound in the heart, he is bound to die, and the reference is to the future. Nor again can there be a harvest where no seed has been sown, nor can a man be at Rome when he is at Athens, nor have been wounded by a sword when he has no scar. Some have the same force when reversed:
a man who breathes is alive, and a man who is alive breathes. Some again cannot be reversed: because he who walks moves it does not follow that he who moves walks.