The Bible is the most widely read, studied, and translated book in history. But if you’ve ever compared a Catholic Bible, a Protestant Bible, and an Orthodox Bible, you’ve probably noticed they’re not identical. Some have 66 books, others 73, and some even more! So, what’s going on?

This post will walk you through how the Reformation came about, why debates over the Bible became central, and how it left us with different canons (or book lists) today.

To make sense of the Reformation, we first have to zoom out. The story of the church before the 1500s is a story of growth, tension, and eventually division.

The Early Church (1st–3rd centuries):
After Jesus’ resurrection, the gospel spread quickly across the Roman Empire. Christians would gather in small communities, but often faced persecution. At this point, there were no denominations. Even though the faith spread through various regions and multiple Latin translations were starting to circulate, the church still saw itself as one body. As early as the second century, Christians were using the word catholic (Greek katholikos, meaning “universal”) to describe the whole worldwide church.

Growth and Structure (4th–5th centuries):
Fast forward to 313 AD, though, and everything changed when Emperor Constantine legalized Christianity. Suddenly, Christians could gather openly, and the church gained both freedom and influence. Leaders (bishops) oversaw regions, and councils gathered to clarify doctrine. One of the most famous was the Council of Nicaea in 325 AD, which gave us the Nicene Creed still used today! (It’s important to note that, while councils like Nicaea clarified core Christian doctrine, biblical canon developed gradually over time rather than being finalized at one single council.)

Regional Differences Begin to Form (4th–5th centuries):
As Christianity continued to spread across the vast Roman Empire, it naturally took on different regional characteristics. In the East (Greece, Asia Minor, Egypt), where Greek was the common language, they were still using the Septuagint (LXX or the Greek translation of the Hebrew Scriptures) as their Old Testament. However, in the West (Italy, North Africa, Spain), where Latin was dominant, dozens of inconsistent Old Latin (Vetus Latina) translations were in circulation.

Because of this, in 382 AD, Pope Damasus I (bishop of Rome) commissioned Jerome (a highly renowned scholar fluent in Latin, Greek, and Hebrew) to create a standardized Latin translation. His work would become one of the most influential projects in Christian history!

The Role of Scripture in the West:
Jerome began his translation work by revising the Gospels against the Greek manuscripts, but when he turned to the Old Testament, he made a controversial choice: instead of sticking only with the Septuagint, he went back to the Hebrew Scriptures wherever possible. While Jerome did still include the additional books found in the Septuagint (later called the Deuterocanonical books), he translated them separately, since no Hebrew versions existed for those texts. He called this approach Hebraica veritas (“the Hebrew truth”). His translation became known as the Latin Vulgate.

Not everyone agreed with Jerome’s approach, though! Figures like Augustine (Saint Augustine of Hippo, a respected bishop and one of the most influential theologians of the early Church) insisted that the Septuagint should retain its primacy, since it had been the church’s Bible from the beginning. But Jerome’s work stuck. The Vulgate became the official Bible of the Western church for over a thousand years. Meanwhile, Eastern Christians continued using the Septuagint. And just like that, a long-term difference was born.

The Great Schism (1054):
As centuries passed, these differences between the Latin-speaking West and the Greek-speaking East grew wider. The West emphasized the authority of the Pope, while the East preferred shared leadership among several major centers. Add in theological disagreements and cultural tensions, and eventually the “Great Schism” split the church in two. From this point forward:

• The West (Roman Catholic Church) was centered in Rome, used Latin as its language of worship, and the Vulgate as its standard Bible.
• The East (Eastern Orthodox Church) was centered in Constantinople, continued to worship in Greek, and preserved the Septuagint as its Old Testament base.

This split didn’t just divide geography; it created two distinct Christian traditions that developed their own liturgy, theology, and biblical heritage.

By the Middle Ages, the Catholic Church held enormous influence in Western Europe. It preserved Scripture and shaped culture, but it also faced serious criticism:

• Corruption and wealth: Some church leaders and clergy were often accused of abusing power, living in luxury, and/or exploiting the faithful.
• Indulgences: A particularly controversial practice was the selling of indulgences, or payments made in exchange for the promise of reduced time in purgatory.
• Spiritual hunger: Many ordinary believers longed for a more personal and Scripture-centered faith.

This was the world Martin Luther, a German Monk and professor of theology, stepped into in the early 1500s. In 1517, Luther nailed his 95 Theses to the church door in Wittenberg, Germany. He protested indulgences and called for a return to the heart of the gospel: salvation by grace through faith in Christ alone!

Luther’s initial goal was not to start a new branch of Christianity; he wanted to reform what already existed. But his challenge to church authority lit a fire that spread quickly across Europe.

At the heart of the debate was this question: Who has ultimate authority? The Church, or Scripture?

The Catholic Church upheld both Scripture and Tradition, with the magisterium (teaching authority of the Church) as the interpreter of both. Reformers, however, championed sola Scriptura (the principle that the Bible alone is the ultimate authority for faith and practice).

This conviction led to some major changes:

• Vernacular translations: Until then, the Latin Vulgate was the standard Bible in the West. Most people couldn’t read Latin, which meant Scripture was out of reach for the average believer. Reformers wanted the Bible in the languages of the people: German, English, French, Dutch, and more!
• Rise of literacy: As Bibles were translated, literacy spread, since people were eager to read Scripture for themselves.
• Bible-centered preaching: Scripture-centered sermons replaced many traditional forms of devotion in Protestant churches, making the Bible the heartbeat of worship!

Once the Bible was in people’s hands, debates over ‘Which books counted as Scripture?’ became unavoidable.

It’s important to note: Luther didn’t originally set out to change the Old Testament canon. Remember, his main battle was with church practices he believed contradicted the gospel. But as the Catholic Church defended certain teachings (such as purgatory, prayers for the dead, and indulgences), they often pointed to the Deuterocanonical books (sometimes called the Apocrypha).

For Luther, these practices felt like abuses of faith. And because the supporting texts came from books not found in the Hebrew canon, he began to question their authority entirely. So, in his 1534 German Bible, Luther included those extra books but moved them to a separate section between the Old and New Testaments. He called them “useful and good to read,” but not equal to the rest of Scripture. Later Protestant Bibles dropped them entirely. (Note: Luther was not the first to point out this distinction. He drew on earlier debates within the church, including Jerome’s preference for the Hebrew canon.)

The Catholic Church, facing the challenge of the Reformation, called the Council of Trent (1545–1563) to clarify doctrine and enact reforms. The council formally reaffirmed the canon of Scripture, including the Deuterocanonical books, as fully authoritative. This wasn’t a “new” decision so much as a reaffirmation of the canon that had been used in the Latin Vulgate for centuries.

From then on, Catholic Bibles contained 73 books (The Hebrew-based Old Testament + Deuterocanonical books + the New Testament) and Protestant Bibles contained 66 books (the Hebrew Old Testament + the New Testament).

Meanwhile, as the Reformation debates played out in Western Europe, the Eastern Orthodox Church continued using the Septuagint, which had an even broader collection of books. That’s why Orthodox Bibles today sometimes include texts like 3 Maccabees, Psalm 151, and the Prayer of Manasseh.

The Reformation also unleashed a wave of Bible translations that shaped the modern Christian world:

• Luther’s German Bible (1534): Brought Scripture to millions of German speakers and deeply influenced the German language itself.
• William Tyndale’s English Bible (1520s–30s): Cost him his life, but laid the foundation for later English Bibles, including the King James Version.
• King James Version (1611): Authorized by the English crown, it became one of the most influential translations in history.
• Other Languages: French, Dutch, Spanish, and Scandinavian translations soon followed, spreading Scripture across Europe.

A Note on Translation: The Bible was originally written in Hebrew, Aramaic, and Greek, and no translation can perfectly capture every wordplay, idiom, or cultural nuance of those original languages. Rest assured, though, this does not mean modern Bibles are untrustworthy. Faithful translations aim to preserve meaning rather than mirror wording exactly, which is why studying multiple translations is not only helpful, but encouraged.

The Bible you open today reflects this history:

• Protestant Bibles: 66 books, following the Hebrew canon.
• Catholic Bibles: 73 books, following the Hebrew canon plus the Deuterocanonical books.
• Orthodox Bibles: Even broader canon, rooted in the Septuagint.

This doesn’t mean one tradition “invented” or “removed” Scripture, but that different branches of Christianity preserved different ancient traditions.

The Reformation reshaped more than just church politics — it changed how Christians everywhere engage with the Bible. It gave ordinary people access to Scripture in their own language, clarified why different traditions have different canons, and left us with many of the translations we still use today.

Understanding this story helps us see not only why Bibles differ, but also how deeply Christians across history have valued God’s Word.