DE MONARCHIA OF DANTE ALIGHIERI
CHAPTER IV: Because the Roman Empire was aided by miracles it was willed of God.
1. Furthermore, whatever is brought to its perfection by the help of miracles is willed of God, and therefore comes to pass by Right. The truth of this is patent from what Thomas  says in his third book against the Heathen: "A miracle is that which is done through divine agency beyond the commonly instituted order of things."  Here he proves that the working of miracles is competent to God alone, and he is corroborated by the word of Moses, that when the magicians of Pharaoh artfully used natural principles to bring forth lice and failed, they cried, "This is the finger of God."  If a miracle, then, is the immediate operation of the First Agent without the cooperation of secondary agents,  which Thomas himself proves clearly enough in the book just cited, then when portents are sent in favor of anything, it is wicked to deny that that thing comes to pass foreseen of God and well pleasing to Him. Hence piety accepts the contradictory, that the Roman Empire gained its perfection with the approval of miracles, that it was therefore willed of God, and consequently that it was and is by Right.
2. And it is established through the testimony of illustrious authors that God revealed His will in miracles in order that the Roman Empire might be brought to completion. For Livy states in the first part of his work that when Numa Pompilius, second king of the Romans, was sacrificing according to the religious rite of the Gentiles, a shield fell from heaven into the chosen city of God.  Lucan recalls this miracle in the ninth book of the Pharsalia in describing the incredible violence which Libya suffers from the south wind, where he says, "It was thus, surely, that to Numa as he sacrificed dropped the shield which the chosen youth of the patrician bears upon his neck in solemn march; south wind or north wind had robbed the peoples wearing our shields." 
3. And when the Gauls, having taken the rest of the city, trusted in the darkness of night to move stealthily to the Capitol, which alone stood between them and utter annihilation of the Roman name, Livy and many other distinguished chroniclers agree that the guards were awakened to defend the Capitol from the approach of the Gauls by the warning cry of a goose, unseen there previously.  This was remembered by Virgil when he described the shield of Aeneas in the eighth book: "On the summit of the Tarpeian citadel, before the temple, Manlius stood guard and held the heights of the Capitol, while the newly builded palace of Romulus was rough with thatch. And here a silver goose flying through golden portals sang the presence of the Gauls on the very threshold." 
4. Also Livy tells among the gests of the Punic Wars that, when the nobility of Rome, overwhelmed by Hannibal, had sunk to such depths that nothing remained for the final destruction of the Roman power but the sacking of the city by the Carthaginians, a sudden and intolerable storm of hail made it impossible for the victors to follow up their triumph. 
5. Was not the flight of Cloelia a miracle? A woman, and captive during the siege of Porsenna, by the wonderful aid of God she rent her fetters asunder and swam the Tiber, as almost all historians  of Rome's affairs remember to that city's glory. Truly it behooved Him so to do, who through eternity foresees all things in the beauty of order.  Invisible He wrought wonders in behalf of things seen, in order that when He should be made visible He might do likewise in behalf of things unseen. 
1. Thomas Aquinas (1225-1274 A. D.), the greatest of Dominicans, the pupil of Albertus Magnus, the friend of St. Bonaventura, and the author of the Summa Theologica, Contra Gentiles, and many other works. Moore points out the extent of Dante's debt to him in Studies, Vol. 1. pp. 311-318. The treatise Contra Gentiles here quoted was written to prove that Christian theology is the "sum and crown of all science."
2. Conv. 3. 7. 8: "The very foundation of our faith is in the miracles done by Him who was crucified, who created our reason and willed it to be less than His power." L.c. 3. 14. 5: "Every miracle may be reasonable to a higher intellect."
3. Exod. 8. 19.
4. Letter 5. 8: "If there is time to survey the affairs of the worlds even to the triumph of Octavian, we shall see that some of them have completely transcended the heights of human valor, and that God has worked somewhat through men, just as through the medium of the new heavens."
5. Liv. 1. 20. 4; 5. 52. 7.
6. Lucan, Phar. 9. 477. Lucan, to whom Dante is indebted "for a considerable amount of poetic material of different kinds," and Dante's relation to him, is discussed by Moore, Studies, Vol. 1. pp. 228-242. It is strange that Dante in this place cites as an instance of supernatural intervention a story which Lucan explains so rationally.
7. Liv. 5.47. So in Conv. 4. 5. 4: "And did not God put forth His hand when the Gauls, having taken all Rome, stole into the Capitol by night, and only the voice of a goose made it known?"
8. Aen. 8. 652-656.
9. Liv. 26. 11; Oros. 4. 17.
10. Liv. 2. 13; Oros. 2. 5; Aurel. Victor, De Viris Illust. c. 13.
11. Par. 8. 97: "The Good which sets in revolution and contents all the realm which thou art scaling, makes its foresight to be virtue in these great bodies."
12. That is, before the birth of Christ the invisible God worked for the visible things of the world. Later, Christ, the visible God, worked for the invisible things of heaven. Cf. the argument at the end of De Mon. 2. 2.