Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
For since rhetoric is composed of them, it follows that:, since a whole consists of parts, these must be parts of the whole which they compose. Those who have called them duties seem to me to have been further influenced by the fact that they wished to reserve the name of parts for another
For each of them contains the whole of rhetoric, since each of them requires invention, arrangement, expression, memory and delivery. Consequently some writers have thought it better to say that there are three kinds of oratory; those whom Cicero [*](de Or. I. xxxi. 141; Top. xxiv. 91. ) has followed seem to me to have taken the wisest course in terming them kinds of causes.
There is, however, a dispute as to whether there are three kinds or more. But it is quite certain that all the most eminent authorities among ancient writers, following Aristotle who merely substituted the term public for deliberative, have been content with the threefold division.
Still a feeble attempt has been made by certain Greeks and by Cicero in his de Oratore, [*](de Or. ii. 10 sq. ) to prove that there are not merely more than three, but that the number of kinds is almost past calculation: and this view has almost been thrust down our throats by the greatest authority [*](Unknown. Perhaps the elder Pliny.) of our own times.