Aristotle, Politics

[1296a] [1] since where some own a very great deal of property and others none there comes about either an extreme democracy or an unmixed oligarchy, or a tyranny may result from both of the two extremes, for tyranny springs from both democracy and oligarchy of the most unbridled kind, but much less often from the middle forms of constitution and those near to them. The cause of this we will speak of later in our treatment of political revolutions. That the middle form of constitution is the best is evident; for it alone is free from faction, since where the middle class is numerous, factions and party divisions among the citizens are least likely to occur. And the great states are more free from faction for the same reason, because the middle class is numerous, whereas in the small states it is easy to divide the whole people into two parties leaving nothing in between, and also almost everybody is needy or wealthy. Also democracies are more secure and more long-lived than oligarchies owing to the citizens of the middle class （for they are more numerous and have a larger share of the honors in democracies than in oligarchies）, since when the poor are in a majority without the middle class, adversity sets in and they are soon ruined. And it must be deemed a significant fact that the best lawgivers are from among the middle citizens; for Solon was of that class, [20] as appears from his poetry, and so was Lycurgus （for he was not a king） and Charondas and almost the greatest number of the other lawgivers.

And these considerations also show the reason why the constitutions of most states are either democratic or oligarchical; owing to the middle class in these states being often a small one, the classes diverging from the middle status—whichever of the two, the owners of the estates or the people, from time to time has the upper hand—conduct the government on their own lines, so that it becomes either a democracy or an oligarchy. And in addition to this, because factions occur and fights between the people and the wealthy, whichever party happens to gain the upper hand over its opponents does not establish a common or equal government, but takes the superior share in the government as a prize of victory, and makes it a democracy in the one case and an oligarchy in the other. Moreover each of the two states that in the past held the leadership of Greece took as a pattern the form of government that existed among themselves and set up in the one case democracies and in the other oligarchies in the cities, not considering the interest of the cities but their own advantage. Hence owing to these causes the middle form of constitution either never comes into existence or seldom and in few places; for one man¹ only among the states that have formerly held the leadership was induced to grant this form of organization, and by this time it has become a fixed habit with the people of the separate cities also not even to desire equality,