The traditional starting point is 1517, when Martin Luther’s Ninety-Five Theses challenged abuses connected to indulgences. Britannica notes that the Theses were written in Latin as propositions for debate and concerned the question of indulgences; according to tradition, Luther posted them at Wittenberg on October 31, 1517. Luther also wrote directly to Archbishop Albrecht of Mainz, protesting the way indulgences were being promoted and warning that people were being given false confidence about salvation.
A key clarification matters: official Catholic teaching did not simply say “buy forgiveness with money.” Even Britannica notes that indulgences were not supposed to imply that divine forgiveness could be bought or sold, especially for the impenitent. The scandal was that abuses and popular misunderstandings had grown around them, especially when indulgences were tied to fundraising, including for St. Peter’s Basilica.
The debate soon moved beyond indulgences. Protestant reformers argued that final doctrinal authority should rest in Scripture, often summarized as sola Scriptura. They also emphasized justification by grace through faith. The Augsburg Confession, one of the foundational Lutheran confessions, states that people are not justified before God by their own strength, merits, or works, but are freely justified for Christ’s sake through faith.
But the Reformation was never one united movement. Luther, Zwingli, Calvin, Cranmer, and later Protestant traditions differed sharply on worship, sacraments, church government, and the Lord’s Supper. Zwingli’s view of the Eucharist, for example, differed from Luther’s, and Calvin’s Institutes of the Christian Religion became a major statement of Reformed theology. Thomas Cranmer shaped the English Reformation and helped produce the Book of Common Prayer, first authorized in 1549.
The movement spread quickly because theology, politics, and technology overlapped. The printing press allowed reforming ideas, pamphlets, sermons, and Bible translations to circulate far more widely than earlier religious controversies could. The Library of Congress notes that Reformation-era works show how printing in Germany became a mass medium as public interest in Luther’s conflict with Rome grew.
The Catholic response was also historically significant. The Council of Trent, held in three periods from 1545 to 1563, became the formal Roman Catholic reply to Protestant doctrinal challenges. It clarified Catholic doctrine, addressed internal discipline, and became central to what is often called the Counter-Reformation.
From an Orthodox-friendly historical perspective, the Reformation should not be treated as a clean “return to the ancient Church.” It exposed serious problems in the medieval West and challenged real abuses, but it also fractured Western Christianity into many competing Protestant traditions. Its legacy is therefore mixed: renewed attention to Scripture and preaching, but also enduring division, confessional conflict, and rival claims about authority.
Primary / historical texts
Martin Luther, Ninety-Five Theses
Martin Luther, Letter to the Archbishop of Mainz, 1517
Augsburg Confession, Article IV: “Of Justification”
Book of Common Prayer, 1549 / 1552 editions
Council of Trent, Canons and Decrees
Scholarly / reference works
Diarmaid MacCulloch, The Reformation: A History
Carter Lindberg, The European Reformations
Euan Cameron, The European Reformation
Brad S. Gregory, The Unintended Reformation
Encyclopaedia Britannica entries on the Ninety-Five Theses, Council of Trent, John Calvin, Huldrych Zwingli, Thomas Cranmer, and the Book of Common Prayer.