Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
The reason which leads me to deal with this subject in this portion of my work is not that I regard character as a matter of indifference where other teachers are concerned, (I have already shown how important I think it in the preceding book), but that the age to which the pupil has now attained makes the mention of this point especially necessary.
For as a rule boys are on the verge of manhood when transferred to the teacher of rhetoric and continue with him even when they are young men: consequently we must spare no effort to secure
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that the purity of the teacher's character should preserve those of tenderer years from corruption, while its authority should keep the bolder spirits from breaking out into licence.