Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
I have, therefore, touched on the topics of humour that I may not be taxed with having omitted them; but with regard to my remarks on the actual practice and manner of jesting, I venture to assert that they are absolutely indispensable. To these Domitius Marsus, who wrote an elaborate treatise on Urbanity, adds several types of saying, which are not laughable, but rather elegant sayings with a certain charm and attraction of their own, which are suitable even to speeches of the most serious kind: they are characterized by a certain urbane wit, but not of a kind to raise a laugh.
And
Urbanity is a certain quality of language compressed into the limits of a brief saying and adapted to delight and move men to every kind of emotion, but specially suitable to resistance or attack according as the person or circumstances concerned may demand.But this definition, if we except the quality of brevity, includes all the virtues of oratory. For it is entirely concerned with persons and things to deal with which in appropriate language is nothing more nor less than the task of perfect eloquence. Why he insisted on brevity being essential I do not know,
since in the same book he asserts that many speakers have revealed their urbanity in narrative. And a little later he gives the following definition, which is, as he says, based on the views expressed by Cato:
Urbanity is the characteristic of a man who has produced many good sayings and replies, and who, whether in conversation, in social or convivial gatherings, in public speeches, or under any other circumstances, will speak with humour and appropriateness. If any orator do this, he will undoubtedly succeed in making his audience laugh.