Happiness itself is sufficient excuse. Beautiful things are right and true; so beautiful actions are those pleasing to the gods. Wise men have an inward sense of what is beautiful, and the highest wisdom is to trust this intuition and be guided by it. The answer to the last appeal of what is right lies within a man's own breast. Trust thyself.
It is clear that those constitutions which aim at the common good are right, as being in accord with absolute justice; while those which aim only at the good of the rulers are wrong.
It has been well said that 'he who has never learned to obey cannot be a good commander.' The two are not the same, but the good citizen ought to be capable of both; he should know how to govern like a freeman, and how to obey like a freeman - these are the virtues of a citizen.
Prudence as well as Moral Virtue determines the complete performance of a man's proper function: Virtue ensures the rightness of the end we aim at, Prudence ensures the rightness of the means we adopt to gain that end.
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.