But there are problems with it.Claims to Roman succession were,with varying degrees of validity,too numerous,anf far too tangled.Ultimately the various claims cancelled one another out and left Europe prostate before the great national kingdoms.

What I dont believe Dante went into any detail on was the relation of the Empire to these budding kingdoms.In theory the Emperor was suzerain over all of Gaul,Iberia,and Britain, as well as Italy.But only the Italian claims were pressed.Perhaps they should not have been.

This brings to the fore a related topic:Imperial policy.How best to exercise power so as to insure a reasonably secure dominion and safeguard not only the practice of Imperial rule,but also its theoretical foundations.

It seems there is consistency with regard to what is meant by the principle of "indirect jurisdiction" of the Catholic Church in its relations with the State going back to the fifth century, at least. In his struggle with Philip the Fair, Boniface VIII issued the bull Unam Sanctam, wherein he declared, "in the power of the Church there are two swords, the spiritual and the temporal--the latter to be used for the Church, the former by the Church; the former by the hand of the priest, the latter by the hand of kings and soldiers, but with the consent and at the pleasure of the priest, ad nutum et patientiam sacerdotis." Continuing, he asserts, "if the temporal power goes astray, it will be judged by the spiritual power, and since this is the supreme power, it can be judged only by God....Consequently, we say, declare, and define that to be subject to the Roman pontiff is necessary for salvation, for every human creature."
The problem is that at the time of the issuing of this bull its true import was lost in the cacophony of the ongoing debate between "legists" (Pierre Flote, for example) and "canonists" (Giles of Rome, for example) as to the nature of the relationship between Church and State: the legists opting for absolute power on the part of the State, and the canonists for the Church.
To help resolve this argument, John of Paris and Dante both sought a via media. Both of their theses were similar, although John's was more clear. Fr. Philip Hughes writes in his "A History of the Church" that John of Paris posited, "The two entities Church and State--though unequal in dignity--are co-ordinate in the exercise of authority. Both originate in the divine plan. The State derives its authority from God no less really than does the Church. The spiritual power is indeed the superior of the two, but it is not superior in everything. The pope, though truly Vicar of Christ by Christ's appointment, is not in fact heir to the totality of Our Lord's universal royalty over men and kings. In its own order the State is, under God, sovereign." Yet, John says the spiritual power has authority to regulate the temporal, because the purpose of the spiritual power is a higher thing than the purpose of the temporal. This regulation is done, however, solely "by instructing the conscience of the prince, and, if the prince fails, by administering correction that is spiritual." This is "indirect jurisdiction" and involves the distinction of the terms supreme and sovereign: the Church and the State are sovereign within their own spheres, but the Church is supreme overall, because of the supernatural destiny of men. Dante, as Dr. Fleming explains, tries to find the via media, also, but seems to give the State (i.e., a universal monarchy) more importance for the happiness of man. Nevertheless, he does admit that the emperor is in some way subject to the Pope "since mortal happiness is in some way established with a view to immortal happiness." Dante says that the emperor receives from the pope "that light of grace by which he may rule more virtuously"
Really, amid all the acrimony between Philip IV and Boniface VIII, this is what the pope was articulating. Not only this, but he was consistent with the Church's teaching on this matter. Pope St. Gregory VII was quite conscious of his responsibility to God for all the souls entrusted to him. "Political activity may be a necessarty means, but the end in view is always wholly supernatural. The pope must answer to God for the souls of kings no less than for those of priests and peasants; for kings too must keep God's law, or find themselves in hell for all eternity." He wrote such thoughts to William the Conqueror and even told that king, "and how you, in turn, because of your salvation and that you may come to the land of the living, must and ought to obey me without delay." In all of this, there is no evidence that the pope was aiming to become the emperor of the Christian State.
As Fr. Hughes notes, this principle of "indirect jurisdiction" was not new even at the time of St. Gregory VII. He cites the instruction of Pope Gelasius to the emperor Anastasius in the fifth century that "the shepherd is charged to guide the whole flock."