Those animals which are incapable of making binding agreements with one another not to inflict nor suffer harm are without either justice or injustic… - Epicurus

Since, of desires some are natural and necessary; others natural, but not necessary; and others neither natural nor necessary, but the offspring of false judgment; it must be the office of temperance to gratify the first class, as far as nature requires: to restrain the second within the bounds of moderation; and, as to the third, resolutely to oppose, and, if possible, entirely repress them.

The happiness which belongs to man, is that state in which he enjoys as many of the good things, and suffers as few of the evils incident to human nature as possible; passing his days in a smooth course of permanent tranquility. A wise man, though deprived of sight or hearing, may experience happiness in the enjoyment of the good things which yet remain; and when suffering torture, or laboring under some painful disease, can mitigate the anguish by patience, and can enjoy, in his afflictions, the consciousness of his own constancy.

Let no one be slow to seek wisdom when he is young nor weary in the search of it when he has grown old. For no age is too early or too late for the health of the soul. And to say that the season for studying philosophy has not yet come, or that it is past and gone, is like saying that the season for happiness is not yet or that it is now no more. Therefore, both old and young alike ought to seek wisdom, the former in order that, as age comes over him, he may be young in good things because of the grace of what has been, and the latter in order that, while he is young, he may at the same time be old, because he has no fear of the things which are to come. So we must exercise ourselves in the things which bring happiness, since, if that be present, we have everything, and, if that be absent, all our actions are directed towards attaining it.