The Ninety-five Theses, written by Martin Luther in 1517, helped ignite the Protestant Reformation and ultimately contributed to the division of Western Christianity.
Originally intended to promote academic debate over indulgences, the theses criticized abuses associated with their use and questioned papal policy. The printing press helped spread Luther’s ideas rapidly throughout Germany, turning a theological dispute into a much broader controversy. The conflict eventually led to Luther’s excommunication from the Roman Catholic Church and contributed to the rise of Protestantism.