De Monarchia (Excerpt)
And as the part is to the whole, so is the order of parts to the order of the whole. The part is to the whole, as to an end and highest good which is aimed at. And, therefore, the order in the parts is to the order in the whole, as it is to the end and highest good aimed at . . . Therefore we find a double order in the world, namely, the order of the parts in relation to each other, and their order in relation to some one thing which is not a part . . . ; and the order of the parts in relation to the one thing which is not a part is the higher, for it is the end of the other order, and the other exists for the sake of it. Therefore, if the form of this order is found in the units of the mass of mankind, much more may we argue by our syllogism that it is found in mankind considered as a whole: for this latter order, or its form, is better. But it is sufficiently plain [that] this order is found in all the units of the mass of mankind. Therefore it is, or should be, found in the mass considered as a whole. And therefore all the parts that we have mentioned, which are comprised in kingdoms, and the kingdoms themselves ought to be ordered with reference to one Prince or Princedom, that is, with reference to a Monarch or Monarchy.
Again, things are well and at their best with every son when he follows, so far as by his proper nature he can, the footsteps of a perfect father. Mankind is the son of heaven, which is most perfect in all its works; for it is "man and the sun which produce man," according to the second book on Natural Learning. The human race, therefore, is best when it imitates the movements of heaven, so far as human nature allows. And since the whole heaven is regulated with one motion, to wit, that of the primum mobile, and by one mover, who is God, in all its parts, movements, and movers (and this human reason readily seizes from science); therefore, if our argument be correct, the human race is at its best state when, both in its movements, and in regard to those who move it, it is regulated by a single Prince, as by the single movement of heaven, and by one law, as by the single motion. Therefore it is evidently necessary for the welfare of the world for there to be a Monarchy, or single Princedom, which men call Empire. And this thought did Boethius breathe when he said: "Oh happy race of men if your hearts are ruled by the love which rules the heaven."
From De Monarchia, by Dante Alighieri, translated by F.J. Church.