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.
Now what is just and right is to be interpreted in the sense of 'what is equal'; and that which is right in the sense of being equal is to be considered with reference to the advantage of the state, and the common good of the citizens. And a citizen is one who shares in governing and being governed. He differs under different forms of government, but in the best state he is one who is able and willing to be governed and to govern with a view to the life of virtue.
The life of theoretical philosophy is the best and happiest a man can lead. Few men are capable of it and then only intermittently. For the rest there is a second-best way of life, that of moral virtue and practical wisdom.
A life of wealth and many belongings is only a means to happiness. Honor, power, and success cannot be happiness because they depend on the whims of others, and happiness should be self-contained, complete in itself.
In seeking for justice men seek for the mean or neutral, for the law is the mean. Again, customary laws have more weight, and relate to more important matters, than written laws, and a man may be a safer ruler than the written law, but not safer than the customary law.
The citizens begin by giving up some part of the constitution, and so with greater ease the government change something else which is a little more important, until they have undermined the whole fabric of the state.
Hence intellect[ual perception] is both a beginning and an end, for the demonstrations arise from these, and concern them. As a result, one ought to pay attention to the undemonstrated assertions and opinions of experienced and older people, or of the prudent, no less than to demonstrations, for, because the have an experienced eye, they see correctly.
Women should marry when they are about eighteen years of age, and men at seven and thirty; then they are in the prime of life, and the decline in the powers of both will coincide.