Martin Luther's 95 Theses

On 31 October 1517, Martin Luther sent his 95 Theses in a letter to Archbishop Albrecht of Mainz, protesting the sale of indulgences and calling for a scholarly debate. According to later accounts, he also posted the theses on the door of the Castle Church in Wittenberg, which served as a kind of public notice board for the university. Whether or not the famous hammer actually struck the door, the theses were quickly copied, printed, and spread far beyond Saxony, igniting the controversy that became the Reformation.