Quintilian, Institutio Oratoria, Book 7
Harold Edgeworth Butler, Ed.

[23] Further, in considering the question of merit, the danger and difficulty of the act will carry great weight, while with regard to liberality it will similarly be of importance to consider the character of the person from whom it proceeds. For liberality is more pleasing in a poor man than in a rich, in one who confers than in one who returns a benefit, in a father than in a childless man. Again, we must consider the immediate object of the gift, the occasion and the intention, that is to say, whether it was given in the hope of subsequent profit; and so on with a number of similar considerations. The question of quality therefore makes the highest demands on the resources of oratory, since it affords the utmost scope for a display of talent on either side, [p. 121] while there is no topic in which the emotional appeal is so effective.