Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
If to this kind of evidence anyone should wish to add evidence of the sort known as supernatural, based on oracles, prophecies and omens, I would remind him that there are two ways in which these may be treated. There is the general method, with regard to which there is an endless dispute between the adherents of the Stoics and the Epicureans, as to whether the world is governed by providence. The other is special and is concerned with particular departments of the art of divination, according as they may happen to affect the question at issue.
For the credibility of oracles may be established or destroyed in one way, and that of soothsayers, augurs, diviners and astrologers in another, since the two classes differ entirely in nature. Again the task of establishing or demolishing such evidence as the following will give the orator plenty to do; as for example if certain words have been uttered under