Final answer:
Indulgences were documents issued by the Catholic Church that could reduce the time a soul spent in purgatory after death. The sale of indulgences, particularly those by Johann Tetzel to fund St. Peter's Basilica, sparked Martin Luther's creation of the Ninety-five Theses and contributed to the start of the Protestant Reformation.
Step-by-step explanation:
Indulgences were a significant aspect of the Catholic Church's practices in the Middle Ages. They functioned as a form of spiritual remittance, whereby individuals could reduce or eliminate the time spent in purgatory for sins after their death, through certain actions or by making a monetary contribution to the Church. Essentially, indulgences were meant to offer the faithful a way to atone for their sins and shorten the period of purification before reaching heaven.
In 1517, the issue of indulgences reached a critical point when Martin Luther, a professor at the University of Wittenberg, reacted to the sale of indulgences by Johann Tetzel, which was occurring nearby. Luther's objections were rooted in his belief that forgiveness for sins could only be granted by God and could not be bought or earned through human actions. His controversy with the Church's practice led to the creation of the Ninety-five Theses, which challenged the Church's authority to grant indulgences and sparked discussions that contributed to the Protestant Reformation.
Pope Leo X's authorization for the sale of indulgences to fund the rebuilding of St. Peter's Basilica in Rome was a key trigger for Luther's discontent. Luther emphasized that salvation could not be secured by financial transactions or the Church's doctrine that merit accumulated by Jesus and the saints could be transferred to others through indulgences. His critique focused on the need for genuine repentance and divine mercy for achieving salvation, rather than relying on purchased indulgences.