We ought to be able to persuade on opposite sides of a question; as also we ought in the case of arguing by syllogism: not that we should practice both, for it is not right to persuade to what is bad; but in order that the bearing of the case may not escape us, and that when another makes an unfair use of these reasonings, we may be able to solve them.
Property should be in a general sense common, but as a general rule private... In well-ordered states, although every man has his own property, some things he will place at the disposal of his friends, while of others he shares the use of them.
There are, then, these three means of effecting persuasion. The man who is to be in command of them must, it is clear, be able (1) to reason logically, (2) to understand human character and goodness in their various forms, and (3) to understand the emotions--that is, to name them and describe them, to know their causes and the way in which they are excited.
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.