Gerbert was born of humble parentage near Aurillac in the ancient French province of Auvergne. He was trained at Saint-Gerald in grammar, arithmetic, and music under the tutelage of Raymond Lavaur, who later became abbot of Aurillac, where Gerbert probably became a monk.

Gerbert was taken to Spain in 967 by Count Borrell of Barcelona and remained there three years. At the monastery of Santa María de Ripoll, which was noted for its fine library, he studied the quadrivium (the higher division of the liberal arts, which includes music, arithmetic, geometry, and astronomy) under Bishop Atto of Vich.

In 970 Gerbert accompanied Borrell to Rome, where his mathematical knowledge delighted the schismatic pope John XIII, who presented him to the Holy Roman emperor Otto I. Gerbert was then entrusted with his first royal pupil, Otto II. Lively Socratic discussions, however, convinced Gerbert that he lacked training in logic, and, when a skilled logician, Archdeacon Gerann of Reims, visited Rome, Gerbert gained permission to study in Reims under Gerann's tutelage.

Logic and dialectic so captivated Gerbert that, after being invited by Adalbero (Adalbero Of Ardennes) (who later ordained him) to teach at the cathedral school, he became famous for reorganizing logical and dialectical studies. Gradually, he eliminated simpler logical works and added monographs on logic by Boethius, an early 6th-century Roman philosopher.

Gerbert's fame aroused the jealousy of Otric, master of the cathedral school at Magdeburg in Saxony (presently in Germany), who denounced Gerbert to Emperor Otto II. In December 980 Otto provoked a debate in Ravenna between Gerbert and Otric on the subject of classifying knowledge. The vehement argument that resulted was terminated only when the Emperor intervened.

Otto subsequently gave Gerbert the headship of the wealthy monastery of St. Columban of Bobbio (southwest of Piacenza, Italy), and Benedict VII consecrated him abbot of the monastery. Gerbert, however, was inexperienced in administration and unfamiliar with the land law in the region of Lombardy. As a result he encountered violent hostility from monks, clerics, and nobles, who possessed much of Bobbio's extensive property through long-term civil-law land leases and refused to make contractual payments or supply troops demanded by Otto. Some even stole the abbey's agricultural products. Within Otto's palace in Pavia (west of Piacenza), nobles plotted against Gerbert and even against Otto himself.

Rebellion followed Otto's death (December 983), forcing Gerbert to flee from Bobbio and hasten to Reims. He travelled and wrote urgent letters to arouse Germans, Belgians, and Lorrainers against Henry II the Quarrelsome, duke of Bavaria, who was plotting to become king by seizing the three-year-old king Otto III. Gerbert resumed teaching at Reims but he really longed to be summoned to the imperial court.

After the deaths of the last Carolingian kings (Lothar in 986 and Louis V in 987), Adalbero and Gerbert influenced the nobles to elect Duke Hugh Capet king against the claims of the remaining Carolingian, Duke Charles (Charles I) of Lorraine. As Hugh's secretary and adviser, Gerbert became involved in Hugh's resistance to Charles's attempt to dethrone him. Before Adalbero died, in January 989, he indicated Gerbert as his successor, but Hugh unwisely chose Arnulf, an illegitimate son of King Lothar. In September Arnulf betrayed Reims to Charles, his uncle, who forced Gerbert to remain in the city. After eight months Gerbert managed to escape to Hugh's court, where he was falsely accused of having been the leader in “enormous crimes” of collaboration with Duke Charles.

In June 990 the bishops and Hugh appealed to Pope John XV to condemn and depose Arnulf and to approve their consecration of a new archbishop. After Hugh captured Charles and Arnulf in March 991, a council at Saint-Basle de Verzy, near Reims, degraded Arnulf. Gerbert was elected archbishop and soon became embroiled in controversies with the papacy. He administered his ecclesiastical duties capably, but the clergy's confidence in the legality of his election decreased. When a newly appointed bishop refused to be consecrated by him and instead travelled to distant Rome for consecration by the Pope, Gerbert hastened to Rome to defend the legitimacy of his election. In the meantime, however, Pope John had died, and Gerbert was heard by John's successor, Gregory V, who rejected Gerbert's plea for support.

Returning north through Pavia, he met Otto III, then 16 and recently crowned emperor. Gerbert's witty intelligence charmed Otto, who immediately made use of his talents for writing letters. They parted reluctantly after Aug. 5, 996. In January 997 a council declared that all bishops involved in Arnulf 's deposition were removed from office. By April Gerbert, no longer tolerating the clergy's acceptance of these decrees, left Reims for Otto's court in Aachen (in modern Germany), never to return to France.

He became a teacher again and a musician in Otto's chapel; he also travelled with Otto to Magdeburg, where he displayed his inventiveness by constructing a timepiece (horologium). In October he followed Otto to Italy, where Otto had him appointed (c. April 998) archbishop of Ravenna, an important city for Otto's control over Italy. Gerbert instigated a new agricultural policy in Italy by having Bobbio's frustrating long-term leases quashed and restricting future leases to the lifetime of the grantor abbot or bishop; this was, perhaps, the most important legislation enacted for Italy during the reign of Otto.

Within a year after Gerbert took over the see of Ravenna, Gregory V died, and Otto was able to choose Gerbert as Gregory's successor. He was consecrated—the first Frenchman to be elevated to the throne of Peter—on April 9, 999, and took the name Sylvester II, declaring his cooperation with Otto's ideal of a renewed Christian Roman Empire.

Their unanimity is shown by numerous documents issued by papal and imperial chanceries that use similar terms. Each appeared as intercessor for a petitioner in documents of the other and also participated in councils of the other. The two men disagreed on only one important political decision, the crowning of Duke Bolesław as king of Poland. Sylvester permitted establishment of Gniezno as an archbishopric independent of the German hierarchy but refused Otto III's desire to elevate Bolesław to kingship. Sylvester did agree, however, to create Stephen king of Hungary and to erect an independent archbishopric there. Otto's sudden death, on Jan. 23, 1002, terminated their close cooperation.

To extend papal influence, Sylvester communicated with Vladimir I, the grand prince of Kiev and first Christian ruler of what became Russia; demanded that King Olaf I Tryggvason of Norway, who made Christianity the official religion of the country, abandon the use of runic writing; sent ambassadors to Dalmatia (on the Adriatic coast of the Balkans); reprimanded the Doge of Venice and the Patriarch of Grado (on the northeastern coast of Italy) for the Venetian clergy's loose morals; held semi-annual general councils; and restored Arnulf to the Reims archbishopric, ending the divisive Reims controversy. He granted Poland its first archbishop (in 1000), and he denounced simony (the buying and selling of ecclesiastical offices) and nepotism and demanded celibacy. Bishops and nobles often exerted authority over wealthy abbeys; the abbeys thus petitioned Sylvester to free them from all exterior control except that of the papacy. Included in their request was the important right to elect their own abbots. Sylvester's acquiescence reduced the power of the bishops and increased that of the pope. To strengthen the papacy still further, Sylvester began its feudalization by enfeoffing Count Daiferio of Terracina in return for military service.

Sylvester died in 1003, and immediately legends about his great learning surfaced, revealing the impression he made on contemporaries. Some attributed his learning to magical arts learned in Spain, some to the devil's coaching, some to an artificial head that answered his questions.

Gerbert was a great scholar, and he was also a good teacher and devised several practical means for learning: a chart for learning rhetoric; his writing about the abacus, which became the basic work on the subject and included the use of Hindu-Arabic numerals, which he had learned in Spain; celestial globes; a hemisphere for learning the imaginary celestial circles; and auxiliary spheres, one for identifying constellations and another with planetary orbits. He acquired an astrolabe and wrote about its uses. He prepared a work on geometry that attempted to fill the gap caused by the existence of a fragmentary Euclid and that included writings by the Roman surveyors. He had an extraordinary knowledge of music and seems to have constructed several organs and also a monochord for studying music theory. His philosophical tract De rationali et de ratione uti (“Concerning the Rational and the Use of Reason”) emphasized problems of definition and classification of knowledge.

Gerbert was an avid collector of manuscripts, which he kept locked in four or five chests; only three of these manuscripts have been identified. He also kept copies of his letters, which were written in good Latin; his original collection has disappeared, but two copies have survived. Only one contemporary biography exists: a work written by Richer of Saint-Rémy, who believed that Gerbert was sent to Reims “by the Divinity Itself.” (This account was discovered only in modern times, in the cathedral library in Bamberg, Ger.) Thus for a long time even learned men relied on legends for knowledge of Gerbert.

Eventually, however, scholars discovered and published critical editions of his writings that dispelled many of the fables that had accumulated around him.

Gerbert remains the dominating figure of the late 10th century for modern scholars, who are concerned especially with more precise dating of his letters and a more detailed understanding of his political roles, his teaching (especially in logic, dialectic, mathematics, and astronomy), his transmission of Arabic learning, his relations with Otto III, his papacy, and his influence on later ages.