Now that practical skills have developed enough to provide adequately for material needs, one of these sciences which are not devoted to utilitarian ends [mathematics] has been able to arise in Egypt, the priestly caste there having the leisure necessary for disinterested research.
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.
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.
Music directly imitates the passions or states of the soul...when one listens to music that imitates a certain passion, he becomes imbued withthe same passion; and if over a long time he habitually listens to music that rouses ignoble passions, his whole character will be shaped to an ignoble form.
The soul consists of two parts, one irrational and the other capable of reason. (Whether these two parts are really distinct in the sense that the parts of the body or of any other divisible whole are distinct, or whether though distinguishable in thought as two they are inseparable in reality, like the convex and concave of a curve, is a question of no importance for the matter in hand.)
All men agree that a just distribution must be according to merit in some sense; they do not all specify the same sort of merit, but democrats identify it with freemen, supporters of oligarchy with wealth (or noble birth), and supporters of aristocracy with excellence.
Money is a guarantee that we may have what we want in the future. Though we need nothing at the moment it insures the possibility of satisfying a new desire when it arises.