Hence that store of knowledge which appears in all his writings.  Geometry, music, grammar, and every useful art, were familiar to him.  He embraced the whole science of logic [e] and ethics.  He studied the operations of nature.  His diligence of enquiry opened to him the long chain of causes and effects, and, in short, the whole system of physiology was his own.  From a mind thus replenished, it is no wonder, my good friends, that we see in the compositions of that extraordinary man that affluence of ideas, and that prodigious flow of eloquence.  In fact, it is not with oratory as with the other arts, which are confined to certain objects, and circumscribed within their own peculiar limits.  He alone deserves the name of an orator, who can speak in a copious style, with ease or dignity, as the subject requires; who can find language to decorate his argument; who through the passions can command the understanding; and, while he serves mankind, knows how to delight the judgement and the imagination of his audience.

XXXI.  Such was, in ancient times, the idea of an orator.  To form that illustrious character, it was not thought necessary to declaim in the schools of rhetoricians [a], or to make a vain parade in fictitious controversies, which were not only void of all reality, but even of a shadow of probability.  Our ancestors pursued a different plan:  they stored their minds with just ideas of moral good and evil; with the rules of right and wrong, and the fair and foul in human transactions.  These, on every controverted point, are the orator’s province.  In courts of law, just and unjust undergo his discussion; in political debate, between what is expedient and honourable, it is his to draw the line; and those questions are so blended in their nature, that they enter into every cause.  On such important topics, who can hope to bring variety of matter, and to dignify that matter with style and sentiment, if he has not, beforehand, enlarged his mind with the knowledge of human nature? with the laws of moral obligation? the deformity of vice, the beauty of virtue, and other points which do not immediately belong to the theory of ethics?

The orator, who has enriched his mind with these materials, may be truly said to have acquired the powers of persuasion.  He who knows the nature of indignation, will be able to kindle or allay that passion in the breast of the judge; and the advocate who has considered the effect of compassion, and from what secret springs it flows, will best know how to soften the mind, and melt it into tenderness.  It is by these secrets of his art that the orator gains his influence.  Whether he has to do with the prejudiced, the angry, the envious, the melancholy, or the timid, he can bridle their various passions, and hold the reins in his own hand.  According to the disposition of his audience, he will know when to check the workings of the heart, and when to raise them to their full tumult of emotion.