The line has magnitude in one way, the plane in two ways, and the solid in three ways, and beyond these there is no other magnitude because the three are all.
In most constitutional states the citizens rule and are ruled by turns, for the idea of a constitutional state implies that the natures of the citizens are equal, and do not differ at all.
The government of freemen is nobler and implies more virtue than despotic government. Neither is a city to be deemed happy or a legislator to be praised because he trains his citizens to conquer and obtain dominion over their neighbors, for there is great evil in this.
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.
In the case of some people, not even if we had the most accurate scientific knowledge, would it be easy to persuade them were we to address them through the medium of that knowledge; for a scientific discourse, it is the privilege of education to appreciate, and it is impossible that this should extend to the multitude.
If we state the function of man to be a certain kind of life, and this to be an activity or actions of the soul implying a rational principle, and the function of a good man to be the good and noble performance of these, and if any action is well performed when it is performed in accordance with the appropriate excellence human good turns out to be activity of the soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete.
The soul has two parts, one rational and the other irrational. Let us now similarly divide the rational part, and let it be assumed that there are two rational faculties, one whereby we contemplate those things whose first principles are invariable, and one whereby we contemplate those things which admit of variation.
It is clear that those constitutions which aim at the common good are right, as being in accord with absolute justice; while those which aim only at the good of the rulers are wrong.