For both excessive and insufficient exercise destroy one's strength, and both eating and drinking too much or too little destroy health, whereas the right quantity produces, increases and preserves it. So it is the same with temperance, courage and the other virtues. This much then, is clear: in all our conduct it is the mean that is to be commended.
AristotleNow, the causes being four, it is the business of the student of nature to know about them all, and if he refers his problems back to all of them, he will assign the "why" in the way proper to his science-the matter, the form, the mover, that for the sake of which.
AristotleHappiness, whether consisting in pleasure or virtue, or both, is more often found with those who are highly cultivated in their minds and in their character, and have only a moderate share of external goods, than among those who possess external goods to a useless extent but are deficient in higher qualities.
Aristotle