[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.
Our virtues are voluntary (and in fact we are in a sense ourselves partly the cause of our moral dispositions, and it is our having a certain character that makes us set up an end of a certain kind), it follows that our vices are voluntary also; they are voluntary in the same manner as our virtues.
A government which is composed of the middle class more nearly approximates to democracy than to oligarchy, and is the safest of the imperfect forms of government.
Error is multiform (for evil is a form of the unlimited, as in the old Pythagorean imagery, and good of the limited), whereas success is possible in one way only (which is why it is easy to fail and difficult to succeed - easy to miss the target and difficult to hit it); so this is another reason why excess and deficiency are a mark of vice, and observance of the mean a mark of virtue: Goodness is simple, badness is manifold.
The precepts of the law may be comprehended under these three points: to live honestly, to hurt no man willfully, and to render every man his due carefully.
Friends hold a mirror up to each other; through that mirror they can see each other in ways that would not otherwise be accessible to them, and it is this mirroring that helps them improve themselves as persons.