Final answer:
Martin Luther's Ninety-five Theses protested the Roman Catholic Church's practice of selling indulgences, which he believed could not influence eternal salvation and undercut the true path to redemption through faith.
Step-by-step explanation:
In the Ninety-five Theses, Martin Luther argued that the Roman Catholic Church's practice of selling indulgences was corrupt and had no bearing on eternal salvation. Luther contended that forgiveness could only be granted by God and that salvation was achieved through faith alone, a principle known as the doctrine of justification by faith. He maintained that the pope had no authority over purgatory and that the accumulation of merit by Jesus and the saints could not be transferred to others through the church.
Luther expressed these concerns in the Ninety-five Theses after Johann Tetzel began selling indulgences in Wittenberg, which were purportedly means to reduce the time souls spent in purgatory. The selling of indulgences, in Luther's view, suggested that entry to heaven could be bought with money rather than gained through repentance and God's mercy—a notion he found deeply troubling. His public opposition to these practices eventually led to the Protestant Reformation, changing the course of Western Christianity.