The Ninety-five Theses or Disputation on the Power of Indulgences[a] is a list of propositions for an academic disputation written in 1517 by Martin Luther, professor of moral theology at the University of Wittenberg, Germany. They advance Luther's positions against what he saw as the abuse of the practice of clergy selling plenary indulgences, which were certificates believed to reduce the temporal punishment in purgatory for sins committed by the purchasers or their loved ones. In the Theses, Luther claimed that the repentance required by Christ in order for sins to be forgiven involves inner spiritual repentance rather than merely external sacramental confession. He argued that indulgences led Christians to avoid true repentance and sorrow for sin, believing that they could forgo it by purchasing an indulgence. They also, according to Luther, discouraged Christians from giving to the poor and performing other acts of mercy, believing that indulgence certificates were more spiritually valuable. Though Luther claimed that his positions on indulgences accorded with those of the Pope, the Theses challenge a 14th-century papal bull stating that the pope could use the treasury of merit and the good deeds of past saints to forgive temporal punishment for sins. The Theses are framed as propositions to be argued in debate rather than necessarily representing Luther's opinions, but Luther later clarified his views in the Explanations of the Disputation Concerning the Value of Indulgences.