Persuasion is effected through the medium of the hearers, when they shall have been brought to a state of excitement under the influence of speech; for we do not, when influenced by pain or joy, or partiality or dislike, award our decisions in the same way; about which means of persuasion alone, I declare that the system-mongers of the present day busy themselves.

Aristotle's Treatise on Rhetoric (ed. 1823)