DE MONARCHIA OF DANTE ALIGHIERI
CHAPTER X: In order to settle all disputes a supreme judge is necessary.
1. Wherever strife is a possibility, in that place must be judgment; otherwise imperfection would exist without its perfecting agent.  This could not be, for God and Nature are not wanting in necessary things.  It is self-evident that between any two princes, neither of whom owes allegiance to the other, controversy may arise either by their own fault or by the fault of their subjects. For such, judgment is necessary. And inasmuch as one owing no allegiance to the other can recognize no authority in him (for an equal cannot control an equal), there must be a third prince with more ample jurisdiction, who may govern both within the circle of his right. This prince will be or will not be a Monarch. If he is, our purpose is fulfilled; if not, he will again have a coequal beyond the circle of his jurisdiction, and again a third prince will be required. And thus either the process will be carried to infinity, which is impossible, or that primal and highest judge will be reached, by whose judgments all disputes are settled mediately or immediately. And this judge will be Monarch, or Emperor. Monarchy is therefore indispensable to the world, and this truth the Philosopher saw when he said, "Things have no desire to be wrongly ordered; inasmuch as a multitude of Princedoms is wrong, let there be one Prince." 
1. "Sine proprio perfectivo."
2. De Anima 3. 9. This idea Dante often repeats. See infra, 2. 7. 2, and 3. 15. 1.
3. Metaphys. 11. 10, at the end. Moore points out the original source as Homer, Il. 2. 204.
Par. 20. 76: "Such seemed to me the image of the imprint of the eternal pleasure, according to its desire for which each thing becomes what sort it is."