I first heard of this work from James Burnham’s book The Machiavellians where he gives it as an example of the futility of philosophical arguments in politics and came across it again recently in Taming of the Prince by Harvey Mansfield in the context of Aristotle’s concept of pambasileia (kingship over all) as one of the good forms of government. As a work of political philosophy De Monarchia is important to adapt Aristotle to the needs of christian monarchy where the pambasileia could be more achievable as a vicar of god like the pope rather than of his own virtue, divine right accomplishing what reason alone could not. However Dante’s reasoning for kingly authority is naturalistic, infered by reason from secondary causes, whereas divine law is by grace but strengthens political authority as both offices are human in nature.
The work is three books, the first on why universal monarchy is necessary for the good of the world which is happiness in this life, the second that the Roman empire was authorized by divine right and did achieve for a time as close to universal order as possible, and the third chapter on the independence of temporal from the spiritual power of the church as expressed by the sun and moon theory, that the moon (kingship) receives its light from the sun (the church).
Book one uses Aristotelian reasoning that there is an end for all things in nature including humanity and there is greater perfection in one than in many, in unity rather than diversity just as there is one god and truth so by analogy it is better there is one head of a household, one ruler of a kingdom, and so there ought to be one ruler of the earth for the end of peace. The ruler must be the freest man, in wealth and power, to be free of self-interest and partiality in order to will justice for humanity based on the principle that necessitous men are not free men. This follows Aristotle’s pambasileia as the king exemplifies humanly virtues (prudence, justice, fortitude, temperance) in the highest degree, the most free man in democracy and the richest man in oligarchy. But the temporal monarch exemplifies these by virtue of the office not personal merit as Dante describes the king as supreme magistrate for the people, an executive of nature law rather than ruling of his own will which is liable to tyranny.
Book two demonstrates Dante’s humanism counter to St Augustine’s city of god that Rome failed to establish justice on earth without divine providence. The Roman empire alone among the ancients achieved the closest to a world empire in the three continents known by Dante Africa, Asia and Europe and Dante quotes Virgil as to the tricontinental origin of the founders of Rome and examples of divine intervention and superior virtues in Roman history. Dante blames the voluntary partitions of the later emperors for the eventual dissolution of the empire. Dante gives the example of the justice of duels in which all parties enter freely and the right of conquest for the greater to rule the lesser by natural or willing submission. Finally, Christ’s beginning and end were justified by Roman authority in the census and punishment by crucifixion, if these were not legal then His sacrifice would be for naught. Christ’s coming at the height of the empire also demonstrates the auspicion of the Roman imperium as to the spread of Christianity.
Book three concludes that because humanity is of two natures, body and soul, there must be two kinds of authority over each to guide humanity towards the best which is god’s intention. The analogy of the sun and moon does not apply because the moon’s entire being does not depend on the light of sun although it is enlightened by it, so does temporal authority reign independently but is strengthened by the spiritual power which both have the same source in god who is one. The role of the church is effectively in educating and organizing believers as to their duties for unlike a temporal leader the pope does not have the authority to change fundamental doctrines as civil law is a human not divine creation. The Caesar owes Peter the same deference a firstborn son owes his father, which is a curious analogy given his sustained case that both offices are of the same human matter but perhaps the spiritual power has priority in being rather than time which is accidental as to the relation of man to man.
Dante intended these arguments for the Holy Roman Empire, the much weakened successor to the Roman empire. But Dante’s arguments are relevant historically as to the relation of religion and state. The divine right of kings was originally a challenge to the authority of the church in worldly affairs rather than often thought a call for theocracy, rather it is religion to have a subordinate or separate role in politics which is strikingly modern.
Aside from the theological aspect, the Aristotelian arguments alone are useful as a philosophical justification of monarchy with analogical and teleological reasoning by way of syllogism. But as Taming the Prince argues, the temporal monarchy develops the idea of the executive who rules on behalf of another, but for Dante as well as for Bodin and the absolutists not for another human but a superior divine and natural right. Dante even reduces the role of Holy Roman electors to declarers and announcers rather than freely choosing the sovereign. We get the idea of law as command rather than deliberation as the sovereign is formally strong but practically weaker as the functions of law are delegated. The strength of the theologico-politico executive relies on popular opinion and Machiavellian prudence rather than innate goodness of character which is also strikingly modern.