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.
But a man's best friend is the one who not only wishes him well but wishes it for his own sake (even though nobody will ever know it): and this condition is best fulfilled by his attitude towards himself - and similarly with all the other attributes that go to define a friend. For we have said before that all friendly feelings for others are extensions of a man's feelings for himself.
The things best to know are first principles and causes, but these things are perhaps the most difficult for men to grasp, for they are farthest removed from the senses.