Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
II. Some regard memory as being no more than one of nature's gifts; and this view is no doubt true to a great extent; but, like everything else, memory
But pleaders need not only to be able to retain a number of facts in their minds, but also to be quick to take them in; it is not enough to learn what you have written by dint of repeated reading; it is just as necessary to follow the order both of matter and words when you have merely thought out what you are going to say, while you must also remember what has been said by your opponents, and must not be content merely with refuting their arguments in the order in which they were advanced, but must be in a position to deal with each in its appropriate place.
Nay, even extempore eloquence, in my opinion, depends on no mental activity so much as memory. For while we are saying one thing, we must be considering something else that we are going to say: consequently, since the mind is always looking ahead, it is continually in search of something which is more remote: on the other hand, whatever it discovers, it deposits by some mysterious process in the safe-keeping of memory, which acts as a transmitting agent and hands on to the delivery
I do not conceive, however, that I need dwell upon the question of the precise function of memory, although many hold the view that certain impressions are made upon the mind, analogous to those which a signet-ring makes on wax. Nor, again, shall I be so credulous, in view of the fact that the retentiveness or slowness of the memory depends upon our physical condition, as to venture to allot a special art to memory.