In the church of the early sixteenth century, forgiveness came in stages. A sinner was to be sorry, confess to a priest, and make satisfaction, through prayers, fasts and alms, for the penalty sin still carried. Whatever remained could be worked off in purgatory or cancelled by an indulgence, a remission the church granted and often sold. Martin Luther, a law student at Erfurt, entered the Augustinian friary there in 1505 to keep a vow he said he had made in a thunderstorm, and his first years as a friar brought what he later called Anfechtungen, attacks of despair over whether God could ever accept him.
The answer he reached is the claim he is remembered for. A person is made right with God, justified in the word he took from Paul, by nothing they do. They are justified by trusting God's promise of forgiveness, which is a gift and cannot be earned. Good works follow from that trust but never produce it: a good person does good works, as a good tree bears good fruit. Luther traced the discovery to a verse in Paul's letter to the Romans about the righteousness of God. In a preface of 1545 he wrote that he had hated the phrase, reading it as the justice by which God punishes sinners, until he understood it as the righteousness God gives to those who believe. Scholars dispute when this happened, proposing dates from about 1514 to 1518 or later.
On 31 October 1517 Luther, by then professor of Bible at Wittenberg, sent Albrecht, archbishop of Mainz, Latin theses against the indulgences being sold in Albrecht's lands. By 1520 he had moved from indulgences to the whole structure of the church, telling the German nobility that every baptized Christian is already a priest, so that a Christian ruler could reform the church when the clergy would not. Pope Leo X excommunicated him on 3 January 1521. That April, before the emperor at the imperial Diet of Worms, he refused to recant, and the edict issued after he left declared him an outlaw. Frederick the Wise, elector of Saxony, had him hidden at the Wartburg castle, where he translated the New Testament into German in eleven weeks.
The same claim set Luther against the philosophy he had been trained in. Theology at the universities was built on Aristotle, whose ethics taught that people become good by doing good acts, the reverse of Luther's order. He wrote theses against that scholastic theology in 1517, and in 1520 asked the universities to drop Aristotle's ethics altogether. He did not reject reason. For the affairs of this life he ranked it above everything else in human beings; he denied only that it could reach what God promises.
Two later positions have weighed on his name ever since. When peasants across Germany rose in the Peasants' War of 1525, Luther urged the princes to put them down by force. In his last years he wrote against the Jews, and On the Jews and Their Lies (1543) called for burning their synagogues and schools. At his Nuremberg trial after the Second World War, Julius Streicher, publisher of the Nazi newspaper Der Stürmer, invoked it in his defence. In 1994 the Evangelical Lutheran Church in America formally repudiated those writings.
His complete German Bible, published in 1534, was among the books that did most to shape standard written German. Philosophers from Lutheran lands, among them Kant, Hegel and Kierkegaard, took up his questions about grace, freedom and the limits of reason. Luther died on 18 February 1546 in Eisleben, the town where he had been born.