By itself, widespread criticism of the church did not lead to the dramatic changes of the sixteenth century. Those resulted from the personal religious struggle of a German university professor and Augustinian friar, Martin Luther (1483–1546).

Martin Luther was a very conscientious friar, but his scrupulous observance of the religious routine, frequent confessions, and fasting gave him only temporary relief from anxieties about sin and his ability to meet God’s demands. Through his study of Saint Paul’s letters in the New Testament, he gradually arrived at a new understanding of Christian doctrine. His understanding is often summarized as “faith alone, grace alone, scripture alone.” He believed that salvation and justification (righteousness in God’s eyes) come through faith, and that faith is a free gift of God, not the result of human effort. God’s word is revealed only in biblical scripture, not in the traditions of the church.

At the same time that Luther was engaged in scholarly reflections and professorial lecturing, Pope Leo X authorized a special Saint Peter’s indulgence to finance his building plans in Rome. An indulgence was a document that substituted for penance. The archbishop who controlled the area in which Wittenberg was located, Albert of Mainz, also promoted the sale of indulgences, in his case to pay off a debt he had incurred to be named bishop of several additional territories. Albert’s sales campaign promised that the purchase of indulgences would bring full forgiveness for one’s own sins or buy release from purgatory for a loved one.

Luther was severely troubled that many people believed that they had no further need for repentance once they had purchased indulgences. He wrote a letter to Archbishop Albert on the subject and enclosed in Latin his “Ninety-five Theses on the Power of Indulgences.” His argument was that indulgences undermined the seriousness of the sacrament of penance and competed with the preaching of the Gospel. Luther intended his theses for academic debate, but by December 1517 they had been translated into German and were being read throughout central Europe. Luther was ordered to go to Rome, but he was able to avoid this because the ruler of the territory in which he lived protected him. The pope nonetheless ordered him to recant many of his ideas, and Luther publicly burned the letter containing the papal order. In this highly charged atmosphere, the twenty-one-year-old emperor Charles V summoned Luther to appear before the Diet of Worms, an assembly of representatives from the territories of the Holy Roman Empire meeting in the city of Worms in 1521. Luther, however, refused to give in to demands that he take back his ideas.