Martin Luther nailed his Ninety-Five Theses to the church door on October 31, 1517, marking a significant event in the Protestant Reformation. The theses challenged the practices of the Catholic Church, particularly the sale of indulgences, which were seen as corrupt and a means to exploit the faithful. This act initiated a widespread debate about Church practices and led to the rise of various Protestant denominations. Luther's actions were pivotal in questioning established religious authority and promoting the idea of faith alone as the path to salvation.