Sylvester (Mazzolini) Prierias entered the early controversy over indulgences when, as papal court theologian, he drafted a theological critique of the 95 Theses that were attached to the letter summoning Luther to Rome in 1518. Born Sylvester Mazzolini in 1456 in the town of Priero, part of the Piedmont region in northwestern Italy, Prierias would later take the Latin form of his hometown for a last name. He joined the Dominican order in 1471 and, while little is known of his family background or early education, by 1493 he had become a noted teacher of Thomistic theology at Pavia, then later Bologna and Rome. He later served as vicar-general of the Lombardian Dominicans from 1508 to 1510. It was Pope Julius II that called the theologian to Rome, where he would join the faculty at the Sapienzia University before being named magistri sacri Palati (“Master of the Sacred Palace”), a court theologian providing advice to Pope Leo X.
By the time of the indulgence controversy, Prierias had attained notoriety for his theological works. Prior to arriving in Rome, he had written numerous vernacular mystical treatises and published his popular Rosa aurea, commentaries on the Gospel lessons for Sundays and feast days throughout the liturgical year. His most notable work, the Summa summarum de casibus conscientiae, or Summa Silvestrina, was a reference manual for confessors that drew on canon law to provide substantial commentary on theological and moral matters. During this period, he became embroiled in a debate amongst the Dominicans, including Cardinal Cajetan, concerning the reason’s ability to demonstrate the immortality of the soul.
Prierias was drafted into the early Reformation conflict while serving in Leo X’s court. After receiving a copy of Luther’s 95 Theses and obtaining a verdict from the faculty at Mainz concerning the theses, Albrecht von Hohenzollern sent an official request to Rome for an investigation of Luther’s teachings. As part of the due process, Leo had canonist Jerome Ghinucci draft a letter summoning Luther to Rome for a hearing and ordered Prierias to provide a theological critique of the theses. Prierias was not unfamiliar with Wittenberg, being present when Luther’s own teacher, Andreas Bodenstein von Karlstadt, underwent a 1516 public disputation in Rome to earn his doctorate in civil and canon law. Afterward, the two had a terse exchange over the role of Scripture in the debate that would suggest the later conflict with Luther.
In 1518, Prierias wrote his Dialogus de potestate papae, which set out a general critique of Luther’s arguments against the theology behind indulgences. Like Johannes Tetzel and Johannes Eck, Prierias embodied the common attempt of Luther’s rivals to shift the debate toward church authority rather than focusing solely on the question of indulgences. He argued that Luther’s theses were methodologically unclear, then offered a fourfold set of principles drawn from the Thomistic tradition for proceeding with debate: the Roman church and the papacy were equivalent with the universal church; neither the Roman church, the papacy, nor a rightly constituted council can err theologically; anyone who disagrees with the infallible proclamations of the Roman church, the papacy, or a council is a heretic; and this judgment extends to both official teachings and official practices. The last of the four would prove the most pivotal to the ensuing debate.
Luther received the Dialogus, along with the summons to appear in Rome within sixty days, on 7 August 1518. He immediately drafted his Responsia to address Prierias’s points and sent them to Frederick the Wise’s secretary, Georg Spalatin, for review on 31 August. Luther contended in his response that indulgences were an unsettled question in the church, so as doctor of Holy Scripture and a teacher in the church he was well within his right to debate them. For Prierias, however, indulgences were an official practice of the church and thus no less authoritative than official teachings. This exposed a deeper rift between the two. Whereas Luther appealed to Scripture, church councils, and canon law, Prierias relied primarily on the theology of Thomas Aquinas and used it support unqualified obedience to papally sanctioned practices as well as dogma. It was in his rejoinder that Luther first cites a claim by fifteenth-century canon lawyer and conciliarist Panormitanus (Nicholas of Tudeschi) regarding the fallibility of both council and pope. Luther would use this argument again in his debate with Eck at Leipzig the next summer, where he began to emphasize to a greater degree the authority of Scripture over all other sources, including canon law and conciliar decrees.
Prierias remained active in the controversy the final years of his life. He wrote two additional treatises against Luther’s position, the Epitoma in 1519 and the Errata et argumenta Martini Lutheris in 1520, but ill health and advancing age prohibited him from contributing further. He would die in Rome in 1523.