"Therefore it is established that every good thing is good because it subsists in unity. As concord is a good thing in itself, it must subsist in some unity as its proper root, and this proper root must appear if we consider the nature or meaning of concord. Now concord is the uniform movement of many wills; and unity of will, which we mean by uniform movement, is the root of concord, or rather concord itself. For just as we should call many clods concordant because all descend together toward the centre, and many flames concordant because they ascend together to the circumference, if they did this voluntarily, so we call many men concordant because they move together by their volition to one end formally present in their wills; while in the case of the clods is formally present the single attribute of gravity, and in the flames the single attribute of levity. For power of willing is a certain potentiality, but the species of goodness which it apprehends is its form, which, like other forms, is a unity multiplied in itself according to the multiplicity of the receiving material, just as soul, number, and other forms subject to composition."
"These things being premised, we may argue as follows for the proposed exposition of the original assumption: All concord depends upon unity in wills; mankind at its best is a concord of a certain kind. For just as one man at his best in body and spirit is a concord of a certain kind, and as a household, a city, and a kingdom is likewise a concord, so it is with mankind in its totality. Therefore the human race for its best disposition is dependent on unity in wills. But this state of concord is impossible unless one will dominates and guides all others into unity, for as the Philosopher teaches in the last book to Nicomachus, mortal wills need directing because of the alluring delights of youth. Nor is this directing will a possibility unless there is one common Prince whose will may dominate and guide the wills of all others. If the conclusions above are true, as they are, Monarchy is essential for the best disposition of mankind; and therefore for the well-being of the world Monarchy should exist therein."
"The Monarch is capable of the highest degree of judgment and Justice, and is therefore perfectly qualified, or especially well qualified, to rule. Those two qualities are most befitting a maker and executor of the law, as that holiest of kings testifies by his petition to God for the attributes meet for a king and the son of a king, praying: 'Give the king thy judgments, O God, and thy righteousness unto the king’s son.'"
A phenomenon not to be forgotten attests the truth of all the arguments placed in order above, namely, that condition of mortals which the Son of God, when about to become man for the salvation of man, either awaited, or ordained at such time as He willed.1 For if from the fall  of our first parents, at which point of departure began all our error, we survey the ordering of men and times, we shall find no perfect Monarchy, nor the world everywhere at peace, save under the divine Monarch Augustus. That  men were then blessed with the tranquillity of universal peace all historians testify, and all illustrious poets; this the writer of the gentleness of Christ felt it meet to confirm, and last of all Paul, who called that most happy condition “the fulness of the time.” Verily, time and all temporal things were full, for no ministry to our happiness lacked its minister. But what has been the condition of the world since that day the seamless robe first suffered mutilation by the claws of avarice, we can read—would that we could not also see! O human race! what tempests must need toss thee, what treasure be thrown into the sea, what shipwrecks must be endured, so long as thou, like a beast of many heads, strivest after diverse ends! Thou art sick in either intellect, and sick likewise in thy affection. Thou healest not thy high understanding by argument irrefutable, nor thy lower by the countenance of experience. Nor dost thou heal thy affection by the sweetness of divine persuasion, when the voice of the Holy Spirit breathes upon thee, “Behold, how good and how pleasant it is for brethren to dwell together in unity!”
--Dante Alighieri, De Monarchia