On both doctrinal and practical grounds Luther felt impelled to attack the system in connection with the Indulgence of 1515-17, which was issued by Pope Leo X. professedly for the rebuilding of St. Peter's. In reality its object was to enable Albrecht of Brandenburg, Archbishop of Mainz, who also held the sees of Magdeburg and Halberstadt, to pay the large debt which he had incurred to the banking house of the Fuggers of Augsburg in payment of the papal dispensation, plus the usual fees, to enable him to acquire the additional office. John Tetzel and other preachers, to whom the archbishop entrusted the business of sell ing the indulgence, were doing a brisk trade in these pardons when Luther, who discovered in the confessional their misleading teach ing on the subject and its nefarious moral and spiritual effects, intervened by posting up his 95 Theses and sending a copy, with a strongly worded letter of protest, to the archbishop. In these theses he distinguished between true repentance and mere penance for sin, maintained that the pope could only remit penalties im posed by his own authority or that of canon law, that God alone can remit the guilt of sin, which is obtained only in the sacra ment of penance, not by papal indulgence, and that in the sacra ment, pope and priest have only a declaratory power of remission, which is due to the grace of God in Christ as proclaimed in the Gospel—the true "Treasure of the Church." He further denied that the remission of canonical penalties through the papal indul gence applies to souls in purgatory, and, whilst recognizing the principle of indulgence in a strictly limited sense, vigorously denounced the false teaching and the pernicious activity of the indulgence preachers, and asserted the right of every penitent Christian to remission apart from this mercenary traffic in pardons.
The proposed disputation did not actually take place. But the theses were widely circulated, both in the original Latin and in a German translation, and before the end of the year were being eagerly read and discussed throughout the empire, and even beyond its bounds. The attack provoked a counter attack on the part of Tetzel and the Dominican Order, of which he was a member, in the form of a series of anti-theses in defence of the traditional doctrine, which, though ascribed to Tetzel, were drawn up by Wimpina, professor of theology in the University of Frank furt-on-the-Oder. In a couple of effusions under his own name, Tetzel roundly accused Luther of heresy and schism ; and a more formidable opponent, John Maier of Eck, otherwise known as Dr. Eck, professor of theology at Ingolstadt, repeated the charge in a communication to the bishop of Eichstadt, entitled "Obe lisks," which, though not printed, was circulated in manuscript. Both Tetzel and Eck maintained that the 95 Theses were an attack on the papal power as well as on a received institution of the Church. Luther replied to Wimpina and Tetzel in a "Sermon on Indulgence and Grace"; to Eck in a series of "Asterisks," in which he stoutly rebutted the charge of heresy. At a congrega tion of his Order at Heidelberg (April 1518) he expounded and defended his distinctive theology, and amplified his theses in a work entitled Resolutiones, which shows a distinct advance in their standpoint, and explicitly emphasizes his fundamental doc trine of justification by faith as the criterion of faith and practice.
This work he sent to the pope as a vindication of his action and a confutation of the charges of his opponents, coupled with a respectful and submissive, but outspoken letter (May 1518).
The issue of a papal decretal on the subject of indulgences left no doubt that Luther's standpoint was irreconcilable with the official doctrine and practice. The attempt of Miltitz, whom the pope sent as his nuncio to Germany to confer the Golden Rose on the Saxon elector, to bring about an accommodation proved fruitless. At a conference at Altenburg in Jan. 1519 Luther went the length of agreeing to refrain from further discussion and to refer the case to the arbitration of a German bishop, on condition that his opponents also observed silence. Miltitz also, in his eagerness to play a role in the case which was not warranted by his commission, sent a misleading report to the pope, repre senting that Luther was not only prepared to refrain from further agitation, but to retract his errors. In reply the pope invited him in a friendly spirit to Rome for this purpose (March 29, 1519). This missive, which never came into Luther's hands, was based on a complete misunderstanding of his real position. What he had refused to Cajetan he was not prepared, at the instance of a busybody like Miltitz, to concede to the pope himself, though at the instigation of the elector he wrote an Instruction to the People, in which, whilst emphasizing the abuses in the institutions of the Church, he still recognized the papal supremacy and the duty of obedience to the Roman Church.