1520 AD
On October 31, 1517, Martin Luther, an Augustinian monk and theology professor at the University of Wittenberg, posted his 95 Theses on the door of the Castle Church in Wittenberg, challenging the practice of selling indulgences and calling for academic debate. The theses were quickly printed and spread throughout Germany and beyond, igniting a movement that would fracture Western Christianity. Luther's theological innovations included sola fide (faith alone), sola scriptura (Scripture alone), and the rejection of sacramental theology, papal authority, clerical celibacy, and the veneration of saints.
The Protestant Reformation spread rapidly across Northern Europe, producing multiple denominations (Lutheran, Reformed/Calvinist, Anglican, Anabaptist) and triggering decades of religious warfare. The Catholic Church responded with the Council of Trent (1545-1563), which clarified Catholic doctrine, reformed abuses, and launched the Counter-Reformation. The Jesuit order, founded by St. Ignatius of Loyola, became a leading force in Catholic renewal and missionary work.
The Catholic Church acknowledges that some of the abuses Luther attacked were real and needed reform, but maintains that his theological departures from Catholic teaching were erroneous. The Joint Declaration on the Doctrine of Justification (1999) between the Catholic Church and the Lutheran World Federation represents significant progress in reconciliation. Key Scripture: Ephesians 4:3-6; John 17:20-23; James 2:14-26; CCC 1814-1816, 2005, 2087