Moral virtue is a mean . . . between two vices, one of excess and the other of defect; . . . it is such a mean because it aims at hitting the middle point in feelings and in actions. This is why it is a hard task to be good, for it is hard to find the middle point in anything.
The virtue of a faculty is related to the special function which that faculty performs. Now there are three elements in the soul which control action and the attainment of truth: namely, Sensation, Intellect, and Desire. Of these, Sensation never originates action, as is shown by the fact that animals have sensation but are not capable of action.
It is this simplicity that makes the uneducated more effective than the educated when addressing popular audiences-makes them, as the poets tell us, 'charm the crowd's ears more finely.' Educated men lay down broad general principles; uneducated men argue from common knowledge and draw obvious conclusions.
Of the tyrant, spies and informers are the principal instruments. War is his favorite occupation, for the sake of engrossing the attention of the people, and making himself necessary to them as their leader.
Men become builders by building and lyreplayers by playing the lyre; so too we become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts.
Therefore the good man ought to be a lover of self, since he will then both benefit himself by acting nobly and aid his fellows; but the bad man ought not to be a lover of self, since he will follow his base passions, and so injure both himself and his neighbors. With the bad man therefore, what he does is not in accord with what he ought to do, but the good man does what he ought, since intelligence always chooses for itself that which is best, and the good man obeys his intelligence.
Money was established for exchange, but interest causes it to be reproduced by itself. Therefore this way of earning money is greatly in conflict with the natural law.