Popularity alone . . . is no test at all of the eloquence of the speaker, no more than velocity alone would be of the force of the external impulse given to the body moving. As in this direction of the body, and other circumstances, must be taken into the account; so in that, you must consider the tendency of the teaching, whether it favors or opposes the vices of the hearers. To head a sect, to infuse party-spirit, to make men arrogant, uncharitable, and malevolent, is the easiest task imaginable, and to which almost any blockhead is fully equal. But to produce the contrary effect . . . is the genuine test of eloquence.
George Campbell, The Philosophy or Rhetoric