The city is a political partnership that comes into being for purposes of self-sufficiency but exists primarily for the sake of living well. Man is by nature a political animal, because he has the ability to communicate and to dialogue and about justice and the good. The city is prior to the individual.
Natural slaves are those who perceive reason but do not have it. It is mutually beneficial that such people be ruled. There are also slaves according to the law, who may or may not be natural slaves. Mastery is rule over slaves, but political rule is rule over free and equal persons.
Holding women, children and property in common as Plato suggests in the Republic is not beneficial to the city. Holding property in common will not reduce factional conflict, but may actually increase because of a sense of injustice.
A citizen in the strict sense is one who shares in making decisions and holding office. Citizenship is therefore essentially democratic, but the notion of citizenship in practice must differ according to the nature of the regime. Commonly speaking, however, a citizen is usually considered to be anyone whose parents are citizens.
The virtue of a good man and an excellent citizen may be different, because the virtue of a citizen is determined with a view to the preservation of the regime. To the extent the actual regime approximates the best regime, the virtue of a good man and an excellent citizen will coincide.
Correct regimes are those which look to the common advantage. Deviant regimes are those which look to the advantage of the rulers, and they involve mastery rather than political rule. The correct regimes are kingship, aristocracy and polity; the incorrect regimes are deviations from those and are tyranny, oligarchy and democracy respectively. Kingship is rule by one person, aristocracy is rule by a few based on merit, and polity is a mixture of democracy and oligarchy. Democracy is rule by the multitude, oligarchy is rule by the wealthy, and tyranny is monarchic rule of a master.
Justice is equality for equals and inequality for unequals. Because the city exists for the sake of living well, virtue must be a care for every city.
Which element of the city should have authority? The multitude may collectively be better judges of certain things, so it is proper for them to share in deliberating and judging, but they should not share in the highest offices. Laws need to be made in accordance with the regime. The just one's regime is, the more just the laws will be. The good of politics is justice. The best claim to rule is education and virtue, but there is also a claim to rule based on wealth and on numbers. A regime must be based on the rule of law.
Polity is the best attainable regime and is formed by the mixture of oligarchy and democracy. A well-mixed polity should reinforce the good parts of each regime while minimizing their shortcomings.
The middling element of city is very important for its stability because it is the most willing to listen to reason and can arbitrate between the very poor and the rich. The middling sort is the least likely to engage in factional conflict, and they make the best legislators. As much as possible, the city should be made up those who are equal or similar.
Factional conflicts arise because of disagreements over justice. There are two types of equality: numerical equality and equality according to merit. Disputes over different claims to justice can lead to conflict and revolution.
To preserve regimes, it is necessary to enforce the laws well, and to arrange offices so that one cannot profit from them. Regimes should take care not to alienate any one portion of the population. The middling element is very important because they tend to mitigate factional conflict. The greatest method of preserving a regime is education relative to the regime, which means education to appreciate the claims of justice that the non-ruling element has.
The problem with democracies is that they define freedom badly, which leads to slavery. The defining principle of democracy is to claim justice as equality based on numbers rather than merit. Citizens in democracies rule and are ruled in turn.
The best regime corresponds to the best way of life for a human being. Since the best way of life is living nobly and according to virtue, the best regime is the one, which promotes this life. The best city needs to be a partnership of similar persons, and rule needs to be based on education and virtue. However, the city needs farmers and laborers to provide sustenance and the material necessities of life. Farmers and laborers do not have the leisure to be well educated and live nobly. Rulers need to come from the leisured classes. The citizens will be exclusively the ruling class, which will rule and be ruled in turn such that the young will be soldiers and the old will rule. All the laboring classes will be slaves.
Education should be common for all citizens, and habituate the children to virtue. Education should consist of letters, gymnastics, music and drawing. Music is important because it is a noble means of using leisure time and through its harmony it makes the student appreciate the harmony of the soul in which reason rules the spirit and the appetites.