In [the soul] one part naturally rules, and the other is subject, and the virtue of the ruler we maintain to be different from that of the subject; the one being the virtue of the rational, and the other of the irrational part. Now, it is obvious that the same principle applies generally, and therefore almost all things rule and are ruled according to nature.
Nature herself, as has been often said, requires that we should be able, not only to work well, but to use leisure well; for, as I must repeat once again, the first principle of all action is leisure. Both are required, but leisure is better than occupation and is its end.
Once you become aware of your own body and its movements, you will be surprised that you are not your body. This is something of a basic principle, that if you can watch something then you are not it. You are the watcher, not the watched. You are the observer, not the observed. How can you be both?
[the virtues] cannot exist without Prudence. A proof of this is that everyone, even at the present day, in defining Virtue, after saying what disposition it is [i.e. moral virtue] and specifying the things with which it is concerned, adds that it is a disposition determined by the right principle; and the right principle is the principle determined by Prudence.
When you build a bridge, you insist that it can carry 30,000 pounds, but you only drive 10,000-pound trucks across it. And that same principle works in investing.