All men agree that a just distribution must be according to merit in some sense; they do not all specify the same sort of merit, but democrats identify it with freemen, supporters of oligarchy with wealth (or noble birth), and supporters of aristocracy with excellence.
Remember that time slurs over everything, let all deeds fade, blurs all writings and kills all memories. Exempt are only those which dig into the hearts of men by love.
The things best to know are first principles and causes, but these things are perhaps the most difficult for men to grasp, for they are farthest removed from the senses.
In the human species at all events there is a great diversity of pleasures. The same things delight some men and annoy others, and things painful and disgusting to some are pleasant and attractive to others.
Some vices miss what is right because they are deficient, others because they are excessive, in feelings or in actions, while virtue finds and chooses the mean.
If purpose, then, is inherent in art, so is it in Nature also. The best illustration is the case of a man being his own physician, for Nature is like that - agent and patient at once.