The Protestant Reformation was initiated by Martin Luther, who published his Ninety-Five Theses in 1517. This document criticized the Catholic Church's practices, particularly the sale of indulgences, and called for a return to biblical principles and personal faith. Luther's actions sparked widespread religious and political upheaval across Europe, leading to the fragmentation of Christianity and the establishment of various Protestant denominations. The Reformation challenged the authority of the papacy and contributed to social transformations in education and governance. Protestant thought heavily influenced cultural developments, paving the way for modernity and redefining the relationship between religion and state.