Born at Lisbon between 1210 and 1220; enthroned, 1276; died at Viterbo, 20 May, 1277. The son of one Julianus, he was baptized Peter, and was known as Petrus Juliani or Petrus Hispanus. After his earlier studies in the cathedral school at Lisbon, he entered the University of Paris and attended lectures on dialectics, logic, and, more particularly, those on Aristotelean physics and metaphysics then being given by Albertus Magnus. The natural philosophy of Aristotle had a special attraction for Peter. He zealously pursued the study of medicine, and also that of theology, attaching himself especially to the Minorite magister, John of Parma. On completing his studies, he was called in 1247 as professor of medicine to the University of Siena, which was at that time being greatly enlarged. Here he wrote his "Summulæ logicales" , for almost three hundred years the favourite textbook on logic. Stapper's investigations (see below) have now established beyond question the authorship of this work. In the fifteenth century the "Summulæ" was translated into Greek by George Scholarius, and was also translated into other languages. In content and form the book is based on the method current at the University of Paris, and on the compendium of William Shyreswood, Peter's professor there. While teaching at Siena, he also made a collection of medical prescriptions.
About 1261 Peter appears in the retinue of Cardinal Ottoboni Fieschi; towards this time also he was made deacon of the Church of Lisbon, an office which he later exchanged for the archidiaconate of Vermuy in the Diocese of Braga. From this period probably dates his acquaintance with Teobaldo Visconti. When, in 1272, Teobaldo came to Viterbo after his election to the papacy as Gregory X, he appointed Petrus Hispanus his physician in ordinary. While occupying this position, the latter wrote his "Thesaurus pauperum", in which he gives a remedy for the diseases of every part of the body. This book was widely used, but was in time variously interpolated. Peter's wide reputation for learning led to his selection as Archbishop of Braga by the cathedral chapter in spring, 1273. Shortly afterwards Gregory X appointed him Cardinal-Bishop of Tusculum, and as such he is referred to on 5 June, 1273. But he continued to govern temporarily the See of Braga until 23 May, 1275, when the pope appointed another archbishop. In June, 1273, Peter accompanied Gregory X to the General Council of Lyons, where he was consecrated bishop. Gregory X's two successors in the Holy See, Innocent V and Adrian V, ruled only a very short time. The latter died at Viterbo on 18 August, 1276, having been elected on the preceding 11 July. In a consistory of cardinals, he had spoken of an alteration in the decrees of Lyons concerning the papal conclave, and had suspended them temporarily. After the death of Adrian V, the conclave in Viterbo was protracted, in consequence of which disturbances broke out in the town, thus hastening the election, so that in the week following 13 September Petrus Juliani, Cardinal-Bishop of Tusculum, was chosen pope, and crowned as John XXI (really XX) the following Sunday (20 September). The new pope wished forthwith to arrange the rules for the conclave. In the Bull "Licet felicis recordationis", ratifying his predecessor's decision, he also suspended with the consent of the cardinals the decrees issued at Lyons, and declared his intention of issuing in the near future the new regulations. On the same day (20 September, 1276) he issued another Bull, directed against those who had taken part in the disturbances during the last council (see CONCLAVE).
The pope was now in a position to turn his attention to the political situation. Since 1263, when Urban IV had bestowed the Kingdom of Sicily upon Charles of Anjou, the latter had tried little by little to strengthen his political power in Rome and the Papal States. Charles himself went to Viterbo to win over the new pope, but the latter did not assent to his plans. On 7 October, the king took the oath of fealty for Sicily, in which it was provided that Sicily should never be united with Tuscany or Lombardy, nor yet with the Roman Empire. The pope, however, did not reappoint him Roman senator, neither did he make him Vicar of Tuscany or Lombardy, honours which Innocent IV had bestowed upon him. In November, John sent an ambassador with letters to Rudolf of Hapsburg, inviting him to send a plenipotentiary to the Curia to negotiate with the plenipotentiary sent by Charles of Anjou concerning the conclusion of peace. As soon as this should be accomplished, Rudolf was to set out for Rome to receive the imperial crown. Soon after, John began negotiations with Rudolf relative to Romagna, the ancient Exarchate of Ravenna, which he wished definitely restored to the Papal States, as Innocent V had already claimed. Concerning the collection and employment of the tithes levied on all ecclesiastical benefices, which the Council of Lyons had ordered in preparation for a crusade, the pope issued various instructions for the different countries. The cross had been taken by Philip III of France and Alfonso of Castile and Leon, and in February, 1276, Philip solemnly declared that he would lead the army in person against the Saracens. But the two kings found themselves involved in a quarrel over the Kingdom of Navarre. The pope laboured to avert the outbreak of hostilities by sending, in November, 1276, legates to both kings, and by remonstrating with the parties in earnest and urgent letters. Soon after this Philip had to disband the large army he had assembled, and a treaty was arranged between the rulers. But in the spring of 1277 the two kings began again to make preparations for war, and again the pope was obliged to send his legates to mediate, wherein they were again successful.
John also endeavoured to secure from the King of Portugal an amelioration of the ecclesiastical conditions in that country, but his pontificate was too short to witness the realization of his purpose. He demanded from Edward I of England the arrears of tribute which that country had owed the Holy See since the reign of King John (1215). He also sought the release of Eleanor, Countess of Montfort, and her brother Amaury, whom King Edward held prisoners. Many letters were sent by the pope to the king and the English bishops relative to this matter. The envoys sent out by the Byzantine emperor, Michael Palæologus, to the Council of Lyons swore that the emperor had renounced the schism, and wished to return to the obedience of the Holy See. In this way the emperor sought to obtain the pope's protection against the Western princes, who threatened his domination. An embassy from Constantinople had already been sent to the Curia in Innocent V's reign, and that pontiff had appointed an envoy to the Byzantine Court, but died before the latter left Italy. Pope John appointed other envoys, two bishops and two Dominicans, and furnished them with minute instructions, as well as with letters for the Emperor Michael, his son Andronicus, and the Greek clergy. In April, 1277, a synod was held at Constantinople under the presidency of the new patriarch, John Beccus, who was an earnest supporter of the union of the Churches. At this synod the emperor and his son embraced the Roman Catholic Faith, and ratified all the promises previously made in their name at the Council of Lyons. The bishops assembled at the synod acknowledged the papal primacy and the doctrine of the Roman Church, and the patriarch addressed a letter to the pope, in which all minor discrepancy in teaching was satisfactorily explained. The messenger, who had charge of this epistle as well as of the documents drawn up by the emperor, did not arrive until after John's death. From the Far East, ambassadors came to the pope from Abaga, Khan of Tatary, who had also sent an embassy to the Council of Lyons. The khan wished to enter into an alliance with the Crusaders and to give them his support; he also asked to have missionaries sent to him. The pope sent the ambassadors to Charles of Sicily, Peter of Aragon, Philip of France, and Edward of England, but none of these sovereigns had any serious intention of undertaking a crusade. John himself appointed missionaries to go to Tatar, but died before they set out on their journey.
Although John showed especial favour towards the University of Paris, he took care to exclude all erroneous teaching from this famous seat of ecclesiastical learning. Some chroniclers maintain that this pope was an enemy of the monks and friars. However, among the documents sent from the papal chancellery under John XXI, there are numerous letters in which he grants privileges and ratifies donations to monasteries. On many occasions, also, he gave evidence of his great respect for the monastic orders. On what particular act of the pope's this adverse criticism is based, is unknown; however, in the most trustworthy accounts of his life, no foundation is found for this reproach. During this pontificate Cardinal Giovanni Gaetano Orsini, who later ascended the papal throne as Nicholas III, exercised a great influence on the government of the Church. Amid the cares of the papacy John found time for his scientific studies, which were more congenial to him than the business of the Curia. To secure the necessary quiet for these studies, he had an apartment added to the papal palace at Viterbo, to which he could retire when he wished to work undisturbed. On 14 May, 1277, while the pope was alone in this apartment, it collapsed; John was buried under the ruins, and died on 20 May in consequence of the serious injuries he had received. Soon after the death of this scholarly pope, various rumours were circulated, based upon his great medical learning; he was even accused of dealing in the magic arts. A few monastic chroniclers, seeing in him an enemy, contributed to these baseless tales, and thus an undeserved stigma was cast upon the memory of John XXI.
GIURAUD AND CADIER, Les Registres de Grégoire X et de Jean XXI (Paris, 1892-8); POTTHAST, Regesta Rom. Pont., II, 1710 sqq.; KOHLER, Vollständige Nachricht von Papst Johann XXI (Göttingen, 1760); STAPPER, Papst Johannes XXI in Kirchengesch. Studen, IV (Münster, 1899), 4; IDEM, Die Summæ logicales des Petrus Hispanus und ihr Verhaltnis zu Michael Psellus in Festschrift des deutschen Campo santo in Rom (Freiburg, 1897), 130-8; GOTTLOB, Die papstlichen Kreuzzugsteuern des 13 Jahrhunderts (Heiligenstadt, 1892); NEUBERGER AND PAGEL, Handbuch der Gesch. der Medezin, I (Jena, 1902), 682, doubt his authorship of the Thesaurus pauperum. For his work on the diseases of the eye, Liber de oculo, see PETELLA, Les connaissances philosophiques d'un médecin philosophe devenu pape in Janus, II (Amsterdam, 1897-98), 405-20, 570-96. The Liber de oculo was first edited, with a German version, by BERGER (Munich, 1899).
J.P. KIRSCH