The structural unity of the parts is such that, if any one of them is displaced or removed, the whole will be disjointed and disturbed. For a thing whose presence or absence makes no visible difference is not an organic part of the whole.
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 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.
For suppose that every tool we had could perform its task, either at our bidding or itself perceiving the need, and if-like the statues made by Dædalus or the tripods of Hephæstus, of which the poet says that "self-moved they enter the assembly of the gods" - shuttles in a loom could fly to and fro and a plectrum play a lyre all self-moved, then master-craftsmen would have no need of servants nor masters of slaves.
I call that law universal, which is conformable merely to dictates of nature; for there does exist naturally an universal sense of right and wrong, which, in a certain degree, all intuitively divine, even should no intercourse with each other, nor any compact have existed.
In the perfect state the good man is absolutely the same as the good citizen; whereas in other states the good citizen is only good relatively to his own form of government.
Friends are an aid to the young, to guard them from error; to the elderly, to attend to their wants and to supplement their failing power of action; to those in the prime of life, to assist them to noble deeds.
Bad people...are in conflict with themselves; they desire one thing and will another, like the incontinent who choose harmful pleasures instead of what they themselves believe to be good.
In practical matters the end is not mere speculative knowledge of what is to be done, but rather the doing of it. It is not enough to know about Virtue, then, but we must endeavor to possess it, and to use it, or to take any other steps that may make.