For they taught their art for a good purpose, to be used against enemies and evil-doers, in self-defence not in aggression, and others have perverted their instructions, and turned to a bad use their own strength and skill. But not on this account are the teachers bad, neither is the art in fault, or bad in itself; I should rather say that those who make a bad use of the art are to blame. And the same argument holds good of rhetoric; for the rhetorician can speak against all men and upon any subject,—in short, he can persuade the multitude better than any other man of anything which he pleases, but he should not therefore seek to defraud the physician or any other artist of his reputation merely because he has the power; he ought to use rhetoric fairly, as he would also use his athletic powers.