(2 Apr. 999–12 May 1003)
On the death of Gregory VEmperor Otto III (996–1002), advised by Abbot Odilo of Cluny (d. 1049), appointed his friend and tutor, Gerbert, then archbishop of Ravenna, to succeed Gregory. The first Frenchman to become pope, he named himself after Silvester I (314–35), traditionally regarded as the model of papal partnership with the emperor.
Born c.945 in Auvergne of humble parentage, he received a thorough education, first at the monastery of Saint-Géraud at Aurillac and then from 967 at Vich, where he became exceptionally proficient in mathematics and astronomy. Taken to Rome in 970 in the entourage of the bishop of Vich, he impressed John XIII by his brilliance and was introduced to Emperor Otto I (962–73). On Easter Sunday, 14 April 972, he was present at the marriage of the Byzantine princess Theophano to the 16-year-old Otto II. The following month he left Rome to study dialectic at Reims, where the archbishop, Adalbero, soon appointed him head of his cathedral school. His renown as a wide-ranging, strikingly original teacher spread, and when visiting the court of Otto II (973–83) at Ravenna with Adalbero in 980 he debated in the emperor's presence with Otric, head of the cathedral school at Magdeburg. Otto was so delighted that he named him abbot of Bobbio, 60 km north-east of Genoa, where he arrved in 982; but in spite of the attractions of the great library he encountered, as a foreigner, such administrative and other practical difficulties that he left the monastery to stay at the imperial court at Pavia, and in the spring of 984 he resumed his teaching at Reims while retaining the title of abbot of Bobbio.
Becoming involved in politics, he assisted Bishop Adalbero in getting Hugh Capet elected king of France (987–96) as best able to reconcile the Carolingians with the Ottonians, whom Adalbero and Gerbert had supported. On Adalbero's death (23 Jan. 989) Gerbert hoped to succeed him at Reims, but Hugh Capet nominated Arnoul, bastard son of the former Carolingian king Lothair (954–86), Gerbert remaining Arnoul's secretary, as he had been of his predecessor. Only when Hugh discovered that Arnoul, who had sworn fealty, was intriguing against him with his rival Charles, duke of Lorraine (d. c.994) who was his uncle, did the king, after vainly awaiting the assent of John XV, have him deposed and replaced by Gerbert at the synod of Saint-Basle, Verzy (17 June 991). Bishop Arnoul of Orléans, furnished with arguments by Gerbert, rejected the plea that papal approval for the deposition was necessary, claiming that synods could judge bishops when the case was clear and determined by law (an early manifestation of Gallicanism), and that in any case the holy see had lost moral credibility, not least by failing to answer the king's letters or receive his ambassadors. John XV, however, refused to recognize Arnoul's enforced resignation, and at the synod of Mouzon (2 June 995) his legate suspended Gerbert, who in the meantime had been openly attacking the papal pretensions. His position at Reims now became untenable, and in spring 996 he betook himself to the court of Otto III, by this time in Rome, becoming his close friend and adviser, and ably defending himself at the coronation synod in May. He returned briefly to Reims, but opposition to him including from the new king Robert the Pious made him again seek refuge with Otto. He travelled with the imperial court to Italy, where Otto built a new palace on the Palatine. His problems at Reims were solved when on 28 Apr. 998 Otto procured his appointment as archbishop of Ravenna, where in his brief time there he set about a programme of reform.