How the Biblical Canon Was Formed
Every Scripture is God-breathed and profitable for teaching, for reproof, for correction, and for instruction in righteousness,2 Timothy 3:16 · World English Bible
Original Language & Text
The word 'canon' means the official list of books that belong in the Bible. Jewish and Protestant Old Testaments have 39 books. But the Old Testament used by most early Christians was a Greek translation called the Septuagint. It included extra books, like Tobit, Judith, Wisdom, Sirach, Baruch, and 1-2 Maccabees, plus extra sections in Daniel and Esther. Catholic and Orthodox Bibles still include these extra books today. Protestant Bibles leave them out, following the shorter Jewish list. Interestingly, the New Testament book of Jude quotes a book called 1 Enoch, which the Ethiopian Orthodox Church treats as scripture but most other churches do not. This shows that a New Testament writer quoting a book does not automatically mean that book belongs in the Bible. For the New Testament, the final list of 27 books first appears, fully spelled out, in a letter written by a church leader named Athanasius in the year 367 CE.
Key Terms in the Original Language
“measuring rod, rule, standard” (Gal. 6:16, Phil. 3:16) — the direct root of the English word “canon”
The word's shift from Paul's sense of a rule of conduct to the later technical sense of “the fixed list of authoritative scriptures” happened gradually over the 2nd–4th centuries, tracked in more detail on the canon timeline.
“writing, Scripture” (2 Tim. 3:16, “all Scripture is God-breathed”)
When this verse was written, “Scripture” for its author almost certainly meant the Hebrew Bible, since most of the New Testament itself was not yet written or collected — a fact relevant to how the verse is later used in debates about the New Testament's own canonicity.
History & Authorship
The Bible's list of books did not come together all at once; it took shape over centuries. For the Old Testament, the first five books (the Torah) were likely settled first, followed a couple centuries later by the books of the Prophets. The rest, called the Writings, were agreed on last, and Jewish teachers kept discussing the exact list well into the rabbinic era. A later Jewish gathering around 90 CE is sometimes linked to closing the list, but many scholars today doubt it actually settled anything. For the New Testament, a teacher named Marcion made his own shorter list in the mid-100s CE, rejecting the Old Testament and keeping only a trimmed Luke and ten of Paul's letters. This pushed mainstream Christians to define their own list more clearly. A document called the Muratorian Fragment, usually dated to around 170-200 CE, names most New Testament books as authoritative and mentions others as still disputed. Later, the scholars Origen and Eusebius sorted books into groups: universally accepted, disputed, and rejected. Regional church meetings at Hippo (393 CE) and Carthage (397 and 419 CE) confirmed the same 27-book New Testament used today, though these were local meetings, not decisions binding the whole church at the time. It wasn't until the Council of Trent in 1546 that the Catholic Church formally locked in its Old Testament list, including the extra books, partly in response to Protestants who had rejected them.
How This Debate Developed
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c. 140
Marcion's canon
The first known attempt at a fixed Christian canon (a trimmed Luke and ten Pauline letters) prompts the wider church to define its own.
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c. 170–200
Muratorian Fragment
The earliest surviving list of New Testament books recognized as authoritative.
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367
Athanasius's Festal Letter 39
First surviving list matching exactly the 27 New Testament books used today.
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397
Council of Carthage
Ratifies the same 27-book New Testament list in the West, formalizing what was already broad consensus.
The Popular / Mainstream View
Most Catholic, Orthodox, and Protestant believers think church leaders did not invent or force the list of Bible books onto everyone. Instead, they believe communities of faith slowly recognized which books were truly inspired by God, based on things like whether an apostle wrote it, whether churches used it regularly in worship, and whether it fit with core Christian teaching. In this view, councils and leaders like Athanasius simply confirmed an agreement that had already grown naturally among believers, rather than creating the list by command, and many who hold this view believe God guided the whole process.
Minority & Alternative Views
Canon formation involved real church politics
Some historians point out that choosing which books belonged in the Bible involved real arguments and church politics, not a smooth, peaceful agreement. Different groups, such as followers of Marcion and various Gnostic Christian groups (movements with their own alternate spiritual teachings), had different lists of sacred writings. Some texts that 'won' were partly chosen because they fit well with the church's growing power structures at the time, not only for the reasons later theology emphasizes.
Different Bibles today show the list was never fully closed
Today, Catholic Bibles have 73 books, Protestant Bibles have 66, Eastern Orthodox Bibles vary (sometimes 76 or more), and Ethiopian Orthodox Bibles have over 80, including books like Enoch and Jubilees. Some scholars say these differences show that deciding the Bible's contents was never one final decision for the whole church. Instead, it was worked out differently in different regions, and debates over certain books (Hebrews, James, 2 Peter, Jude, and Revelation in the East, and the extra Old Testament books generally) continued from the 300s all the way to the 1500s and beyond.
Other ancient writings show wider early Christian diversity
Discoveries like the Nag Hammadi library, found in 1945, which contains Gnostic gospels and other writings, and the Dead Sea Scrolls show that many more religious texts circulated among Jews and Christians in ancient times than the ones that eventually made it into the Bible. This suggests today's Bible reflects a selection made from many real options, not simply the only writings that ever existed.
What Scholars Say
Historians widely agree that choosing the Bible's books was a slow process lasting centuries, not one final decision. A core group of books, like the first five books of the Old Testament, the four Gospels, and Paul's major letters, gained wide acceptance earlier than disputed books like Hebrews, James, 2 Peter, Jude, and Revelation, which some regions kept debating into the 300s CE and later. No serious historian disputes that the different Old Testament lists, Jewish/Protestant versus Catholic/Orthodox/Ethiopian, reflect real historical differences rather than one single ancient tradition everyone agreed on. Different faith traditions disagree on how to explain this history in theological terms, seeing it either as God guiding a natural process or as a more human, situational one, but the basic historical facts and timeline are not seriously disputed by scholars of any faith background.
What the Confessions Say
Reformed
“The books commonly called Apocrypha, not being of divine inspiration, are no part of the Canon of the Scripture; and therefore are of no authority in the Church of God, nor to be any otherwise approved, or made use of, than other human writings.”
Westminster Confession of Faith (1646), 1.3
Catholic
“The Synod... receives and venerates... all the books both of the Old and of the New Testament... as also the said traditions... with an equal affection of piety and reverence.”
Council of Trent (1546), Fourth Session, De Canonicis Scripturis
Sources & Further Reading
- Bruce M. Metzger, The Canon of the New Testament
- Lee Martin McDonald, The Formation of the Christian Biblical Canon
- The Muratorian Fragment (c. 2nd-4th century CE)
- Athanasius of Alexandria, 39th Festal Letter (367 CE)
- Council of Trent, Decree on Sacred Scripture (1546)
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- What role did the Muratorian Fragment and Athanasius's 39th Festal Letter play in the historical process of defining the New Testament canon?
- How do scholars like Bruce Metzger and Lee Martin McDonald differ in how "closed" or contested they consider the canonization process to have been?
- What does the existence of divergent canons — Catholic, Protestant, Eastern Orthodox, Ethiopian — suggest about whether canon formation was ever fully settled?
- What does material from Nag Hammadi and Qumran reveal about the wider range of early Jewish and Christian literature that did not make it into any canon?
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