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2.2 Luther and the Protestant Reformation

🇪🇺AP European History
Unit 2 Review

2.2 Luther and the Protestant Reformation

Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 examWritten by the Fiveable Content Team • Last updated September 2025
🇪🇺AP European History
Unit & Topic Study Guides
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This topic and 2.3 (Protestant Reform Continues) both focus on the Protestant Reformation. However, 2.2 primarily examines its causes. While the causes of the Reformation are complex, we will focus on key reformers and their beliefs.

Timeline

This timeline contextualizes key events leading to the Protestant Reformation:

  • 1492: Erasmus is ordained as a Catholic priest.
  • 1507: Martin Luther is ordained as a Catholic priest.
  • 1509: Erasmus writes and publishes Praise of Folly in Latin.
  • 1517: Luther nails his 95 Theses to the door of the church in Wittenberg. This event is widely considered the beginning of the Protestant Reformation.
  • 1521: Luther refuses to recant his writings at the Diet of Worms and is declared an outlaw by the Edict of Worms.
  • 1522: Luther translates the New Testament into the German vernacular.
  • 1524: The German Peasants' War begins.
  • 1529: Luther publishes his Catechism.
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Who Was Martin Luther?

Martin Luther was a German monk and theologian. Records depict him as a dedicated religious scholar who took matters of faith, particularly salvation, very seriously. Although initially a Catholic priest, he grew increasingly critical of the Catholic Church’s perceived hypocrisy and abuses.

The 95 Theses

In 1517, while serving as a lecturer in Wittenberg, Martin Luther wrote his 95 Theses, criticizing the sale of indulgences—documents that allegedly reduced time in purgatory.

Key Point: Luther intended his 95 Theses to spark an academic debate rather than an outright rebellion. Posting such documents on the church door was a common practice.

However, due to the printing press, Luther’s criticisms spread rapidly. By 1518, his views had ignited controversy, and his theological beliefs evolved toward the doctrine of salvation by grace alone—rejecting the idea that good works or indulgences could secure salvation.

Causes of the Protestant Reformation

Check 2.1 Contextualizing 16th and 17th-Century Challenges and Developments for a full understanding of the specific reasons for Martin Luther’s and other’s dissatisfaction of the church. As a quick reminder:

  • Indulgences: Documents sold by the Catholic Church that absolved individuals of sins and reduced time in purgatory. Essentially, the Church claimed that by paying money, people could secure salvation for themselves or their family members.
  • Clerical Immorality: Many clergy members broke Church rules, engaging in behaviors like drunkenness and violating their vows of celibacy.
  • Believed the Bible should be accessible to common people in their native/vernacular language.
  • Pluralism: Holding multiple church positions simultaneously, leading to corruption and neglect of duties.

Defining the Protestant Reformation

A clear definition of the Protestant Reformation is essential for answering SAQs, DBQs, and LEQs:

⭐ The Protestant Reformation was a 16th-century religious movement that challenged the authority of the Catholic Church, leading to the establishment of Protestant denominations and significant religious, political, and social changes across Europe.

Diet of Worms (1521)

In 1521, Luther was summoned to the Diet of Worms, an imperial assembly, where he was asked to recant his writings.

(Note: A "Diet" was an assembly, and "Worms" was the city where it was held.)

Luther refused, reportedly stating:

“Here I stand. I can do no other. God help me. Amen.” (This statement, though widely attributed to Luther, may be apocryphal.)

As a result, Luther was excommunicated and declared an outlaw by the Edict of Worms, meaning anyone could legally kill him. He took refuge in Wartburg Castle, where he continued his work.

Image Courtesy of Wikimedia

Protestantism

Unlike the Catholic Church, Protestantism does not have a single unifying institution. As a result, many different Protestant sects emerged as followers of Luther and others developed their own interpretations of Christian faith. Check the table at the bottom of the study guide for the differences between Lutheranism and Catholicism.

John Calvin and Calvinism

One key reformer influenced by Luther was John Calvin (1509–1564), a French theologian who founded Calvinism.

==A defining belief of Calvinism is predestination: the idea that God has already determined who will be saved (the elect) and who will be damned. Since individuals could not know their fate, Calvinists often viewed wealth and prosperity as signs of divine favor.==

Later, sociologist Max Weber argued that Calvinist attitudes toward work and prosperity contributed to the development of capitalism, coining the term Protestant Work Ethic.

Responses to Luther and Calvin

Luther and Calvin inspired other reformers and movements:

  • Ulrich Zwingli led reforms in Switzerland, emphasizing the Bible as the sole authority in faith.
  • The Anabaptists rejected infant baptism and opposed state involvement in religion, leading to their persecution.
  • Luther’s ideas also influenced the German Peasants’ Revolt (1524–1525), though he ultimately condemned the uprising.

Core Protestant Beliefs

Protestants not only rejected Catholic hierarchy but also developed distinct theological beliefs:

  1. Sola fide (faith alone): Salvation comes through faith in Jesus Christ, not good works or indulgences.
  2. Sola scriptura (scripture alone): The Bible is the sole authority in matters of faith, rejecting Catholic traditions such as saint veneration.
  3. Priesthood of all believers: Every believer has direct access to God without needing clergy as intermediaries.

Comparison: Catholicism vs. Lutheranism

CatholicismLutheranism
Continuities
SaviorJesus ChristJesus Christ
Holy BookBibleBible
Changes
Authority of the PopeConfirmedDenied
Sole AuthorityThe PopeThe Bible
ClergyChurch Hierarchy"Priesthood of all believers"
Confession of SinsThrough priests to GodThrough prayers to God
Means of SalvationFaith and Good WorksFaith Alone (Sola fide)
Place of WorshipLarge Ornate ChurchesSimple Churches

This concludes the overview of 2.2 Luther and the Protestant Reformation. The next section, 2.3 Protestant Reform Continues, will examine the expansion and consequences of Protestant movements across Europe.

🎥 Watch: AP European History - Martin Luther and Reformation

🎥 Watch: AP European History - Reformation 2.0

Vocabulary

The following words are mentioned explicitly in the College Board Course and Exam Description for this topic.

TermDefinition
AnabaptistsA radical Protestant group that rejected infant baptism and refused to recognize the subordination of the church to secular state control.
CalvinistsFollowers of John Calvin who believed in predestination and often viewed economic success as evidence of God's favor.
Catholic abusesCorrupt or improper practices within the Catholic Church that reformers criticized, such as the sale of indulgences.
Christian doctrineThe official teachings and beliefs of the Christian Church regarding faith and salvation.
PredestinationThe theological doctrine that God has already determined which individuals will achieve salvation and which will not.
Priesthood of all believersA Protestant doctrine asserting that all Christians have direct access to God and can interpret scripture without requiring a priestly intermediary.
Primacy of scriptureThe Protestant principle that the Bible is the ultimate authority for Christian doctrine and practice, above church tradition and papal authority.
religious practicesThe rituals, ceremonies, behaviors, and convictions through which people express and live out their faith.
Salvation by faith aloneThe Protestant belief that salvation is achieved through faith in God and Christ alone, without the need for works or church sacraments.
wealth accumulationThe gathering and increase of material possessions and economic resources.

Frequently Asked Questions

What is the Protestant Reformation and why did it happen?

The Protestant Reformation was a 16th-century movement that broke Western Christianity into new churches (like Lutheranism and Calvinism) and forced big changes in belief, politics, and society. It started because of Catholic abuses—especially the sale of indulgences and clerical corruption—and new ideas: Renaissance humanism, emphasis on scripture (primacy of Scripture), and Martin Luther’s claim that salvation is by faith alone (Sola Fide) and that all believers share a “priesthood of all believers.” Luther’s 95 Theses (1517), the printing press, and political rulers who wanted independence from Rome let these ideas spread fast. Reactions included radicals (Anabaptists), peasant unrest, the Diet of Worms, the German Peasants’ War, the Catholic Reformation, and eventually legal recognition in the Peace of Augsburg. On the AP exam this fits Unit 2 Learning Objective B and shows up in MCQs, SAQs, and DBQ/LEQ prompts. For a focused review use Fiveable’s Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history).

Who was Martin Luther and what did he actually do?

Martin Luther was a German monk and university professor who kicked off the Protestant Reformation. In 1517 he challenged the Catholic practice of selling indulgences by posting the 95 Theses and arguing salvation is by faith alone (sola fide), Scripture is supreme (primacy of Scripture), and all believers share a “priesthood of all believers.” His ideas spread fast thanks to the printing press. Key moments: the Diet of Worms (1521) where he refused to recant, the social fallout including the German Peasants’ War, and the formation of Lutheran churches. Luther’s theology helped create new Protestant interpretations (Lutheranism) and forced political responses like the Peace of Augsburg (1555), which allowed rulers to choose their territory’s religion. For AP Euro, link his criticisms of indulgences and doctrinal changes to KC-1.2.I.B and use documents/short-answer prompts to show how religion and politics changed 1450–1648 (see the Topic 2.2 study guide: https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu). For practice, try problems at (https://library.fiveable.me/practice/ap-european-history).

Why did Luther criticize the Catholic Church so much?

Luther criticized the Catholic Church mainly because he saw serious doctrinal and practical abuses that blocked honest faith. He attacked indulgences and the idea that money or church rituals could buy forgiveness, arguing instead sola fide (salvation by faith alone), the primacy of scripture, and the priesthood of all believers—ideas spelled out in the 95 Theses and later writings. Those beliefs challenged clerical authority and Rome’s wealth, and the printing press spread his critique fast across Germany, forcing political responses (Diet of Worms) and drawing in rulers and peasants (e.g., German Peasants’ War). Luther’s goal wasn’t chaos but reforming doctrine and practice; his critique sparked new Protestant churches (Lutheranism) and long-term religious change (see CED keywords: Indulgences, Sola Fide, Primacy of Scripture, Priesthood of all believers). This content often shows up on AP multiple-choice and free-response items—use the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and Unit 2 overview (https://library.fiveable.me/ap-european-history/unit-2) for review, and practice questions (https://library.fiveable.me/practice/ap-european-history) to prep.

What's the difference between Catholic and Protestant beliefs?

Short answer: The core differences center on authority and how you’re saved. Catholics teach that salvation comes through faith plus the church’s sacraments, good works, and church authority (pope, priests); the church interprets Scripture and mediates grace (indulgences were a flashpoint). Protestants (Lutherans, Calvinists, Anabaptists) rejected that: they emphasized sola scriptura (primacy of Scripture), sola fide (salvation by faith alone), and the priesthood of all believers (no special spiritual caste). Luther emphasized justification by faith; Calvin added predestination and a stricter moral order (and some Calvinists linked wealth to God’s favor). These disagreements—spread fast because of the printing press—led to religious fragmentation, political conflict, and settlements like the Peace of Augsburg (religious choice for princes). For AP Euro, focus on doctrinal terms (sola fide, priesthood of all believers, primacy of Scripture, predestination) and link beliefs to political effects. Use the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history) to prep.

Can someone explain predestination in simple terms because I'm so confused?

Predestination = the idea that God already decided—before you were born—who will be saved (go to heaven) and who won’t. John Calvin pushed this inside Protestantism: humans can’t earn salvation by works; God’s choice is final. Simple effects to remember for AP Euro: it stressed God’s absolute power (sovereignty), gave some believers a strong sense of "calling" or assurance, and in Calvinist communities led people to value hard work and moral discipline (which later tied to ideas that wealth could signal God’s favor). For the exam, connect predestination to Calvinism, "salvation by faith alone," and changes in religious practice/ social behavior (CED Topic 2.2). Want a quick review? Check the Topic 2.2 study guide on Fiveable (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and try practice questions (https://library.fiveable.me/practice/ap-european-history) to see how it shows up on multiple-choice or LEQ/SAQ prompts.

How did John Calvin's ideas differ from Martin Luther's?

Short answer: both rejected Catholic abuses and the need for works for salvation, but they differed on theology and church order. Luther taught sola fide (salvation by faith alone), the priesthood of all believers, and the primacy of Scripture; he kept a more conservative view of sacraments and favored state-supported regional churches (Lutheran princes). Calvin emphasized absolute divine sovereignty and predestination (God already elects who’s saved), built a stricter moral discipline through church governance (consistory), and promoted a theocratic-leaning community where church and civic life reinforced holiness. Calvinism also encouraged a work ethic and the idea that worldly success could signal God’s favor. Both are key AP CED concepts (Sola Fide, Primacy of Scripture, Predestination, Lutheranism, Calvinism). For more practice and review, check the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and thousands of practice questions (https://library.fiveable.me/practice/ap-european-history).

What were the 95 Theses and why were they such a big deal?

The 95 Theses were Martin Luther’s list of objections (1517) mainly against the sale of indulgences and the idea that money could buy forgiveness. Luther argued salvation is by faith alone (sola fide), that Scripture—not church hierarchy—has primacy, and that ordinary Christians share a “priesthood of all believers.” They mattered because: 1) they challenged core Catholic practices and authority (KC-1.2.I.B), 2) the printing press let them spread quickly across German lands, turning a local debate into a wider movement (Lutheranism → Protestant Reformation), and 3) they set off political and social reactions (Diet of Worms, German Peasants’ War, wars of religion). For AP prep, you should connect the Theses to CED keywords like indulgences, primacy of scripture, sola fide, and the printing press; those show up on multiple-choice, short-answer, and DBQ prompts. Review the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history).

Why did some Protestant groups think being rich meant God liked you more?

Some Protestant groups—especially Calvinists—treated wealth as a sign of God’s favor because of how their theology connected predestination, vocation, and visible signs. Calvin taught that God elects (predestination), but since you can’t know your election directly, believers looked for “fruit” of election in their lives. Hard work, disciplined living, and business success became evidence that you lived according to God’s calling (a “calling” or vocation). Over time this encouraged a cultural link between thrift, profit, and spiritual approval—what the CED summarizes as some Protestants viewing wealth as a reward for hard work (KC-1.2.I.C). On the AP exam, this idea shows up in prompts about changing religious beliefs and social effects in the Reformation era (use Topic 2.2 study guide for review: https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu). For more practice connecting religion to economic/social changes, try Fiveable’s practice problems (https://library.fiveable.me/practice/ap-european-history).

What's the priesthood of all believers supposed to mean?

“Priesthood of all believers” is Luther’s idea that every Christian has direct access to God and can read/interpret Scripture without needing a priest as mediator. It challenged the Catholic claim that only ordained clergy could fully administer sacraments or interpret doctrine. Practically, it pushed for vernacular Bibles, encouraged personal Bible reading (primacy of Scripture), weakened clerical authority, and helped spread ideas through printing and rising literacy. In AP terms, it’s one of the New Protestant interpretations of Christian doctrine (alongside sola fide and primacy of Scripture) and helps explain why reformers reshaped church structure and encouraged lay religious participation. You should know it for short-answer and essay questions about religious change in 1450–1648. For a focused review, check the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history).

How do I write a DBQ essay about the causes of the Protestant Reformation?

Start with a clear thesis that answers the prompt (one sentence in intro or conclusion)—e.g., “The Protestant Reformation was caused primarily by religious critiques of Catholic practice, amplified by social and political factors.” Contextualize briefly: late-medieval church abuses, Renaissance humanism, and the printing press. Use at least four documents to support your claim and one specific outside fact (e.g., Luther’s 95 Theses, Sola Fide, or the Diet of Worms). Explain POV/situation for at least two documents (who wrote it and why) to show source awareness. Structure body paragraphs around causes: theological (indulgences, sola fide, primacy of scripture), technological (printing press), political (German princes seeking autonomy), and social (Peasant unrest). End with a complexity point: show interaction/shift between religious motives and political self-interest. For topic review check Fiveable’s study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history).

What were the main consequences of the Protestant Reformation on European society?

The Protestant Reformation reshaped European society in four big ways. First, religious fragmentation: Luther, Calvin, and radicals (Anabaptists) broke Christian unity, creating new confessions—Lutheranism, Calvinism—and the “priesthood of all believers,” sola scriptura, and sola fide (faith alone). Second, political change: princes and states used Protestantism to assert authority (secularization of power), leading to conflicts like the German Peasants’ War and decades of religious wars that ended with the Peace of Augsburg and later Westphalia. Third, social/economic effects: some Protestants (especially Calvinists) linked hard work and wealth to God’s favor, changing attitudes toward work and capitalism. Fourth, cultural/technological spread: the printing press spread reform ideas, increased literacy, and encouraged scripture-centered worship. These consequences show up on the AP exam in MCQs, LEQs, and DBQs—use evidence like the 95 Theses, Diet of Worms, and Peace of Augsburg. For a focused review, see the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and try practice questions (https://library.fiveable.me/practice/ap-european-history).

I don't understand why German peasants got involved in religious reform - can someone explain the connection?

Religious reform mattered to German peasants because Protestant ideas challenged the church’s spiritual authority and—crucially—gave language that peasants used to question social and economic injustices. Concepts like the “priesthood of all believers” and “primacy of scripture” (CED keywords) suggested ordinary people could read and interpret the Bible themselves, so they began to demand fairer treatment, fewer tithes, and relief from serf-like obligations. Economic stress (high rents, taxes, crop failures) made those religious claims more explosive. That mix of religious language + social grievances helped spark the German Peasants’ War (1524–25), where peasants invoked reform rhetoric for political and economic change. Importantly, Martin Luther’s message inspired their language but he rejected violent revolt—showing how reform could have unintended social consequences (KC-1.2.I.B). For a quick review, see the Topic 2.2 study guide on Fiveable (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu). For practice, try AP-style questions at Fiveable’s practice page (https://library.fiveable.me/practice/ap-european-history).

Who were the Anabaptists and how were they different from other Protestant groups?

Anabaptists were radical Reformation groups who believed baptism should be for consenting adults only (rejecting infant baptism), so people must choose faith for themselves. They pushed for a clear separation between church and state, voluntary church membership, and often formed tight-knit, sometimes communal, communities. Some Anabaptists practiced nonresistance and refused to swear oaths or hold public office, which made them politically suspect. How they differed: mainstream Protestants (Lutherans, Calvinists) kept infant baptism, accepted some cooperation with secular rulers, and built state churches (e.g., Lutheranism). Calvinists emphasized predestination and often supported disciplined, prosperous civic life; Anabaptists rejected that synthesis and threatened both Catholic and Protestant authorities—so they were persecuted by both. On the AP exam, Anabaptists are an example of “religious radicals” as responses to Luther/Calvin (CED KC-1.2.I.B). For a quick review, see the Topic 2.2 study guide on Fiveable (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu). For extra practice, try problems at (https://library.fiveable.me/practice/ap-european-history).

What does "salvation by faith alone" actually mean and how is it different from Catholic teaching?

"Salvation by faith alone" (sola fide) means you're made right with God only through trusting Christ—not by doing good works, buying indulgences, or relying on priestly actions. For Luther, faith is the sole means God accepts; good works follow as evidence of true faith, but they don't earn salvation. Catholic teaching in the 16th century held that faith plus works and the sacraments mattered: salvation involved grace received through the Church, participation in the seven sacraments, penance, and acts of charity. The Church also taught that indulgences could reduce punishment for sin (which Luther criticized). So the key difference: Protestants (Lutherans) emphasized sola fide and the priesthood of all believers and primacy of Scripture, while Catholics emphasized faith cooperating with works and the Church’s sacramental role (see AP Topic 2.2 study guide for more: https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu). For extra practice, try AP-style questions at https://library.fiveable.me/practice/ap-european-history.

How did the Protestant Reformation change the relationship between church and state in Europe?

The Reformation shifted church–state relations from a Europe-wide Catholic hierarchy to a patchwork of confessional states where rulers often chose religion. Reformers (Luther, Calvin) promoted the priesthood of all believers, sola scriptura, and sola fide, which undercut papal and clerical authority and made religious belief more personal and local. Secular princes used that opening to assert control over churches in their territories (state-sponsored Lutheran and Calvinist churches), producing the principle cuius regio, eius religio (formalized later in the Peace of Augsburg). That meant religious loyalty became a tool of state-building: monarchs enforced confessions, taxed churches, and used reform to legitimize political power. The result was fragmentation of Christendom, more secular decision-making about worship and property, and increased religious wars—all topics AP prompts (DBQ/LEQ) ask you to analyze with documents and broader context. For a focused review, see the Topic 2.2 study guide (https://library.fiveable.me/ap-european-history/unit-2/martin-luther-protestant-reformation/study-guide/ArfgDlWtrakuA4dYbHNu) and practice questions (https://library.fiveable.me/practice/ap-european-history).