Martin Luther's 95 Theses sparked the Reformation

On October 31, 1517, the day before the Feast of All Saints, the 33-year-old monk and professor Martin Luther circulated his Ninety-five Theses at Wittenberg, in Saxony. By tradition he posted them on the door of the Castle Church, then a customary notice board for academic debate, though scholars dispute whether any nailing actually occurred.

The Latin theses attacked the sale of indulgences — payments that promised to reduce punishment for sins — then being aggressively peddled to fund the rebuilding of St. Peter’s Basilica in Rome. Luther meant to invite scholarly argument, not to break with the Church.

He lost control of the document. Others translated it into German, ran it through the new printing press, and within weeks it had spread across the German lands and made Luther famous. The dispute escalated until his 1521 excommunication, by which point the rupture was permanent. The episode is conventionally treated as the beginning of the Protestant Reformation, which reshaped European religion and politics for centuries.