Aristotle, Politics

[1293a] [1] And a fourth kind of democracy is the one that has been the last in point of time to come into existence in the states. Because the states have become much greater than the original ones and possess large supplies of revenue, while all the citizens have a share in the government because of the superiority¹ of the multitude, all actually take part in it and exercise their citizenship because even the poor are enabled to be at leisure by receiving pay. Indeed the multitude in this kind of state has a very great deal of leisure, for they are not hampered at all by the care of their private affairs, but the rich are, so that often they take no part in the assembly nor in judging lawsuits. Owing to this the multitude of the poor becomes sovereign over the government, instead of the laws. Such in number and in nature are the kinds of democracy that these causes necessarily bring into existence. To turn to the varieties and of oligarchy, when more men possess property, but less of it and not a very large amount, this is the first form of oligarchy; for they allow the man that acquires property the right to participate, and because there is a large number of persons participating in the government it necessarily follows that not the men but the law is sovereign （for the farther removed they are from monarchy, and as they have not so much property as to be idle and neglect it, nor yet so little as to be kept at the expense of the state, [20] they are compelled to call upon the law to rule instead of ruling themselves）. But then if the owners of the properties are fewer than those who owned them previously, and own more, the second form of oligarchy comes into being; for as they become stronger they claim to have a larger share, and therefore they themselves select those from among the rest of the citizens who go into the government, but as they are not yet strong enough to rule without law they make the law conform with this.² And if they carry matters further by becoming fewer and holding larger properties, there comes about the third advance in oligarchy, which consists in their keeping the offices in their own hands, but under a law enacting that they are to be hereditary. And when finally they attain very great pre-eminence by their wealth and their multitude of friends, a dynasty of this nature is near to monarchy, and men become supreme instead of the law; and this is the fourth kind of oligarchy, the counterpart of the last kind of democracy.

Furthermore³ there are two constitutions by the side of democracy and oligarchy, one⁴ of which is counted by everybody and has been referred to as one of the four forms of constitution （and the four meant are monarchy, oligarchy, democracy and fourth the form called aristocracy）, but there is a fifth, entitled by the common name of them all （for it is called constitutional government）, but as it does not often occur it is overlooked by those who try to enumerate the forms of constitution, and they use the four names only （as does Plato） in the list of constitutions.