Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Still we do not keep our attention rigidly fixed on such details, but the desire to win praise by any available means and the sheer delight in speaking make us wander away from the subject, since there is always richer material for eloquence outside the strict theme of the case, inasmuch as the points of any given dispute are always few, and there is all the world outside, and in the one case we speak according to our instructions, in the other on the subjects of our own choice.
We should teach not so much that it is our duty to discover the question, the central argument, and the point for the decision of the judge (an easy task), as that we should continually keep our attention on our subject, or if we digress, at least keep looking back to it, lest in our desire to win applause we should let our weapons drop from our grasp.
The school of Theodorus, as I have said, groups everything under heads, by which they mean several things. First they mean the main question, which is to be identified with the basis; secondly they mean the other questions dependent on the main question, thirdly the proposition and the statement of the proofs. The word is used as we use it when we say
It is the head of the whole business,or, as Menander says, κεφάλαιόν ἐστιν. [*]( Perhaps a gloss referring to the late rhetorician Menander. If genuine, the words must refer to the comic poet. ) But generally speaking, anything which has to be proved will be a head of varying degrees of importance.