It seems worth while to go over the list of Popes who came during the twenty years just before and after the date given for the issuance of this supposed bull.
Eugene IV, elected Pope in 1431, whatever may have been his faults of lack of tact, was scholarly and unselfish. At an early age he distributed what was really an immense fortune in his time to the poor, and entered the monastery. When political troubles drove him from Rome he resided at Florence and the presence of the Papal Court there did much to foster the humanistic movement which was just then beginning. It was he who consecrated the beautiful church just finished by Brunelleschi.
His successor in 1447 was Pope Nicholas V, a man of wide education and deep interest in the revival of classical literature and Christian antiquities. He was the founder of the Vatican Library and brought Fra Angelico to Rome for the great decorative work at the Vatican.
Pope Calixtus III, who succeeded Nicholas in 1455, was a man of cultivated mind, scholarly tastes and shared with his predecessor the honor of having founded the Vatican Library. He encouraged the Greek scholars in Italy and added greatly to the collections of precious manuscripts. His desire to prevent the further destruction of Greek culture by the Turks who had just captured Constantinople, led him to devote himself mainly to the fulfilment of a vow that he had made to wrest Constantinople from the Moslem. To his influence is largely due the victory gained by the Christians at Belgrade at this time which prevented the further spread of Mohammedan power. Pope Calixtus had the Angelus Bell rung every day at noon to implore the aid of the heavenly powers against the Turks. There is absolutely no question of any reference in this matter to the comet, but here is where the story comes in.
Pope Calixtus’ successor was the famous Renaissance scholar AEneas Sylvius Piccolomini. He was just beginning some of the reforms, the need of which had been pointed out by his friend, the scholarly Nicholas of Cusa, when his death occurred as a consequence of his fatigue in journeys undertaken to rouse the Christians of the West against the Turks so as to preserve Christian civilization.
His successor was Pope Paul II. He found it necessary to suppress some of the academies of Rome whose privileges were being abused by fostering a pagan attitude toward philosophy and religion, and in revenge Platina wrote a bitter biography of him, but no one has ever doubted of his scholarliness. He built the Palace of St. Marco in Rome, now known as the Venezia, and organized relief work among the poor while encouraging printing, protecting universities, and showing himself a judicious collector of works of ancient art.
James J. Walsh, The Popes and Science (1908)