Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
And, indeed, since words in themselves count for much and the voice adds a force of its own to the matter of which it speaks, while gesture and motion are full of significance, we may be sure of finding something like perfection when all these qualities are combined.
There are some, however, who consider that delivery which owes nothing to art and everything to natural impulse is more forcible, and in fact the only form of delivery which is worthy of a manly speaker.
Those, however, who think it sufficient for men to be born to enable them to become orators, are welcome to their opinion, and I must ask them to be indulgent to the efforts to which I am committed by my belief that we cannot hope to attain perfection unless nature is assisted by study. But I will not be so obstinate as to deny that to nature must be assigned the first place.