DE MONARCHIA OF DANTE ALIGHIERI
CHAPTER X: Argument from the donation of Constantine. 
1. In addition, some persons affirm that the Emperor Constantine, healed of leprosy by the intercession of Sylvester, then the Supreme Pontiff  gave to the Church the very seat of Empire, Rome, together with many imperial dignities.  Wherefore they argue that no one has power to assume these dignities except he receives them from the Church, to whom it is asserted they belong. And from this it would fairly follow, as they desire, that one authority is dependent on the other.
2. So having stated and refuted the arguments which seemed to be rooted in divine communications, it now remains to set forth and disprove those rooted in Roman deeds and human reason. We have just spoken of the first of these, whose syllogism runs thus: Those things which belong to the Church no one can rightly possess, unless granted them by the Church; and this we concede. The ruling power of Rome belongs to the Church; therefore no one can rightly possess it unless granted it by the Church. And the minor premise they prove by the facts mentioned above concerning Constantine.
3. This minor premise, then, I deny. Their proof is no proof, for Constantine had not the power to alienate the imperial dignity, nor had the Church power to receive it. Their insistent objection to what I say can be met thus. No one is free to do through an office assigned him anything contrary to the office, for thereby the same thing, in virtue of being the same, would be contrary to itself: which is impossible. But to divide the Empire would be contrary to the office assigned the Emperor, for as is easily seen from the first book of the treatise, his office is to hold the human race subject to one will in all things. Therefore, division of his Empire is not allowed an Emperor. If, as they claim, certain dignities were alienated by Constantine from the Empire and ceded to the power of the Church, the "seamless coat"  would have been rent, which even they had not dared to mutilate who with their spears pierced Christ, the very God. Moreover, as the Church has its own foundation, so has the Empire its own. The foundation of the Church is Christ, as the Apostle writes to the Corinthians: "Other foundation can no man lay than that is laid, which is Jesus Christ."  He is the rock on which the Church is founded,  but the foundation of the Empire is human Right. Now I say that as the Church cannot act contrary to its foundation, but must be supported thereby, according to that verse of the Canticles: "Who is she that cometh up from the desert, abounding in delights, leaning on her beloved?"  so the Empire cannot act in conflict with human Right. Therefore the Empire may not destroy itself, for, should it do so, it would act in conflict with human Right. Inasmuch as the Empire consists in the indivisibility of universal Monarchy, and inasmuch as an apportionment of the Empire would destroy it, it is evident that division is not allowed to him who discharges imperial duty.  And it is proved, from what has been previously said, that to destroy the Empire would be contrary to human Right.
4. Besides, every jurisdiction exists prior to its judge, since the judge is ordained for the jurisdiction, and not conversely. As the Empire is a jurisdiction embracing in its circuit the administration of justice in all temporal things, so it is prior to its judge, who is Emperor; and the Emperor is ordained for it, and not conversely. Clearly the Emperor, as Emperor, cannot alter the Empire, for from it he receives his being and state. So I say, either he was Emperor when he made the concession they speak of to the Church, or he was not. If he was not, it is plain that he had no power to grant anything with regard to the Empire. And if he was, then as Emperor he could not have done this, for the concession would have narrowed his jurisdiction.
5. Further, if one Emperor has power to cut away one bit from the jurisdiction of the Empire, another may do the same for like reason. And since temporal jurisdiction is finite, and every finite thing may be consumed by finite losses, the possibility of annihilating primal jurisdiction would follow. But this is inconceivable.
6. And since he who confers a thing has the relation of agent, and he on whom it is conferred the relation of patient, according to the Philosopher in the fourth book to Nicomachus, then in order for a grant to be legal, proper qualification is essential not only in the giver, but in the recipient.  Indeed, it seems that the acts of agents exist potentially in a properly qualified patient. But the Church was utterly disqualified for receiving temporal power by the express prohibitive command in Matthew: "Provide neither gold, nor silver, nor brass in your purses, nor scrip for your journey," etc.  For although we learn from Luke  of the mitigation of this order regarding certain things, yet I am unable to find that sanction was given the Church to possess gold and silver, subsequent to the prohibition. Wherefore if the Church had not power to receive, even had Constantine power to bestow, temporal authority, the action would nevertheless be impossible, because of the disqualification of the patient. It is demonstrated, then, that neither could the Church accept by way of possession, nor could Constantine confer by way of alienation. However, the Emperor did have power to depute to the protectorship of the Church a patrimony, and other things, as long as his supreme command, the unity of which suffers no impairment, remained unchanged. And the Vicar of God had power to receive such things, not for possession, but for distribution on behalf of the Church of its fruits to the poor of Christ.  We are not ignorant that thus the Apostles did.
1. Near the end of the eighth century the decretals and donation of Constantine were forged, documents which purported that when that Emperor removed his capital to Byzantium, 324 A.D., he left Rome in order to give to the Church temporal sway in the western world. That this donation was a forgery was not discovered until 1440 by Laurentinus Valla. See Gibbon, vol. 6. 49 (notes 68-76), the Milman-Smith edition. It is scarcely necessary to add that Dante had firm faith in the genuineness of the donation.
2. Inf. 27. 94: "Constantine sought Sylvester within Soracte to heal him of his leprosy." This legend Butler thinks Dante took from Brunetto, Tresor, Bk. 1. Pt. 2. c. 87, but Toynbee traces it to the Legenda Aurea of Jacobus de Voragine. See Toynbee, Studies, p. 297. Cf. De Regim, Princ. 3. 16.
3. The donation is mentioned De Mon. 2. 12. 2; 2. 13. 5; 3. 13. 4.
Inf. 19. 115: "Ah, Constantine, of how great ill was mother, not thy conversion, but the dowry which the first rich pope got from thee."
In the vision of Church and Empire, Purg. 32, the worldly wealth of the papacy is thus described 1. 124: "Next from thence, whence it had before come, I saw the eagle come down into the ark of the car, and leave it feathered with itself;" line 136: "That which remained, like ground alive with herbage, covered itself again with feathers, offered haply with sound and benign intention, and was covered again."
The eagle describes Constantine Par. 20. 54: "The second who follows, with the laws and with me, under a good intention which bore ill fruit, to give way to the Pastor, made himself a Greek. Now knows he how the ill deduced from his good work is not harmful to him, albeit that the world be thereby destroyed."
4. John 19. 23, 24, 34. The seamless robe is again used as the type of undivided monarchy De Mon. 1. 16, and note 6.
5. 1 Cor. 3. 11.
6. Matt. 16. 18.
7. Can. 8. 5 (Vulg. ). The English version has not the words "deliciis effluens," "abounding in delights." Dante quotes the verse, as here, in Conv. 2. 6. 2, as definitely signifying the Church.
8. Witte refers to Engelbertus Admonteus, De Ortu et Fine Rom. Imp. 18: "It was not permitted that the Emperor Hadrian or Jovinian should surrender the imperial boundaries, ... nor has it been, nor will it be permitted to any Emperor, because then would it fall from the name and dignity of Augustus, which means that the Empire should be augmented and not diminished."
9. Eth. 4. 1. 8: "The liberal man will give for the sake of the honorable, and will give properly, for he will give to proper objects, in proper quantities, at proper times."
10. Matt. 10. 9.
11. Luke 9. 3; 10. 4.
12. De Mon. 2. 12. 1, and note 2.