Few questions generate as much confusion — and suspicion — as "who decided which books would be in the Bible?" Novels, documentaries, and popular theories suggest secret votes, manipulative emperors, and books "banned" for political convenience. The historical reality is far less dramatic, and at the same time far more solid: the biblical canon was not born from a single decision, but from a long, communal, and verifiable process of recognition.
Understanding how the Bible was formed is not just an academic exercise. It's a question of trust: why do we trust that these 66 books — and not others — carry God's authority? This guide walks through the formation of the Old and New Testaments, the criteria the church used to recognize inspiration, the councils that confirmed the canon, and why different Christian traditions have slightly different book lists.
This topic connects directly to the reliability of the biblical text as a whole. If you haven't yet read about what the inerrancy of Scripture means, it's worth reading in sequence — one article deals with the origin of the books, the other with the reliability of what is written in them.
What Is the Biblical Canon? Definition and Origin of the Word
The word "canon" comes from the Greek kanon, which originally meant a measuring rod — a fixed standard used to check whether something was straight, correct, aligned. Applied to Scripture, the word came to mean the official list of books recognized as inspired by God and therefore normative for Christian faith and practice.
It's important to note the difference between canonizing and making authoritative. The church did not confer authority on the biblical books by way of a vote, the way a law gets approved. The process ran the other way: the books were already considered authoritative by communities of faith — read, quoted, and used in worship — and the canon simply formalized, documented, and delimited a recognition that already existed.
The Protestant Bible gathers 66 books: 39 in the Old Testament and 27 in the New Testament. Catholic and Orthodox Bibles include additional Old Testament books, called deuterocanonical or apocryphal, depending on the tradition — a point this article explains in more detail further on.
How the Old Testament Canon Was Formed
The Old Testament didn't appear all at once — it was composed over more than a thousand years, by different authors, across different periods of Israel's history. The Torah (the first five books) was recognized as sacred Scripture very early, likely already settled by around the 5th century BC. The Prophets and the Writings were progressively added over the following centuries.
By the first century of the Christian era, the Jewish people already operated with broad consensus about which books made up their sacred Scriptures. The Jewish historian Flavius Josephus, writing around 95 AD in Against Apion, describes 22 sacred books — a different grouping from ours, but one that corresponds to the same content as today's 39-book Protestant Old Testament, simply organized and counted differently.
A common myth attributes the closing of the Old Testament canon to a supposed "Council of Jamnia," held by Jewish rabbis around 90 AD. More recent historical research questions this version: there is no solid evidence that Jamnia was a formal council with the authority to decide the canon. It is more likely to have been an academic discussion about books already widely accepted for generations — not a decision that created the canon out of nothing.
Jesus and the apostles, when quoting "the Law, the Prophets, and the Psalms" (Luke 24:44), were already referring to a recognized and stable collection of Hebrew Scriptures in their own time, decades before any later rabbinic debate.
The Septuagint and the Apocryphal Books
Starting in the 3rd century BC in Alexandria, the Hebrew Old Testament was translated into Greek — a translation known as the Septuagint (or LXX, traditionally attributed to 70 translators). This version became the most widely read Bible in the Hellenized Mediterranean world, including among many Jews of the diaspora and, later, among most New Testament writers, who frequently quote the Old Testament from it.
The Septuagint, however, circulated with an additional set of writings — books like Tobit, Judith, Wisdom, Sirach, Baruch, and 1-2 Maccabees — that were not part of the Palestinian Hebrew canon. These books are today called "deuterocanonical" by Catholic and Orthodox tradition, or "apocryphal" by Protestant tradition.
Jerome himself, translator of the Latin Vulgate in the 4th century, already made this distinction. He championed the principle of hebraica veritas — the priority of the original Hebrew text — and classified the books unique to the Septuagint as useful for edification, but not on the same level of doctrinal authority as the canonical Hebrew books. Even so, he included them in the Vulgate under ecclesiastical pressure, and Augustine, his contemporary, held a more favorable position toward including these books.
This disagreement between Jerome and Augustine in the 4th century is, in practice, the same disagreement that would centuries later divide Catholics and Protestants over the Old Testament — not a new dispute, but a tension present since the church's earliest centuries.
How the New Testament Canon Was Formed
Unlike the Old Testament, the New Testament was written over a relatively short period — most scholars place its 27 books between roughly 45 and 100 AD, within the apostolic period or shortly after it. From very early on, these writings were already treated as Scripture.
Colossians 4:16
"And when this epistle is read among you, cause that it be read also in the church of the Laodiceans; and that ye likewise read the epistle from Laodicea."
2 Peter 3:15-16
"...even as our beloved brother Paul also according to the wisdom given unto him hath written unto you... which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction."
1 Timothy 5:18
"For the scripture saith, Thou shalt not muzzle the ox that treadeth out the corn. And, The labourer is worthy of his reward."
Around 170 AD, the so-called Muratorian Fragment — the oldest known list of New Testament books — already recognizes most of today's 27 books, including the four Gospels and most of Paul's letters. One factor that accelerated the need for clarity was Marcion, a heretical leader who, around 140 AD, proposed his own reduced canon — just an edited version of Luke and ten of Paul's letters, rejecting the entire Old Testament. The orthodox church's reaction to Marcion helped, by contrast, speed up the clear articulation of what was already widely accepted.
The Criteria for Canonicity: How the Church Recognized the Inspired Books
The early church did not apply a single, mechanical test to accept or reject books. Historians identify, however, three recurring criteria used — more descriptively than prescriptively — to explain why certain writings were already recognized as Scripture.
Apostolicity — the book was written by an apostle or by someone in close association with an apostle (like Mark, associated with Peter, or Luke, Paul's companion). This criterion explains why many popular but late or anonymous writings were never seriously considered for the canon.
Orthodoxy — the book's content had to conform to the "rule of faith" already taught by the apostles and passed down in the churches. Later Gnostic texts, such as the so-called "Gospel of Thomas," were rejected precisely because they contradicted established apostolic teaching, not by arbitrary decision.
Catholicity — the book had to enjoy broad and continuous acceptance across churches, not just circulate in one isolated region. Books like Hebrews, James, 2 Peter, 2-3 John, Jude, and Revelation — the so-called antilegomena, or "disputed books" — took longer to reach this universal consensus, but were eventually recognized.
It's worth acknowledging honestly: the process wasn't instantaneous or free of debate. Eusebius of Caesarea, a 4th-century historian, explicitly documents different categories — "recognized," "disputed," and "spurious" books — showing that the church took its time reaching a consensus, rather than simply decreeing one from the top down.
The Councils That Confirmed the Canon: Hippo and Carthage
The earliest known document to list exactly the 27 New Testament books we have today — not one more, not one less — is Athanasius of Alexandria's Easter Festal Letter, written in 367 AD. Athanasius wasn't inventing a new list: he was putting into writing the consensus that already circulated widely among the churches of his time.
"These are the springs of salvation, so that he who is thirsty may be satisfied with the words they contain. In these alone the teaching of godliness is proclaimed. Let no one add to them or take anything from them." — Athanasius of Alexandria, Festal Letter of 367 AD, referring to the list of the 27 New Testament books.
A few decades later, the regional councils of Hippo (393 AD) and Carthage (397 and 419 AD), in North Africa, under strong theological influence from Augustine, formally ratified that same 27-book New Testament list. It's crucial to understand the nature of these councils: they were regional assemblies, not a "universal ecumenical council" convened specifically to vote on the canon — and they confirmed, rather than created, a consensus that had already existed for generations.
Was the Canon "Decided" by the Church or Simply Recognized?
This is perhaps the most important question in this article, because popular theories — popularized by fiction like The Da Vinci Code — suggest that Emperor Constantine or a later council "chose" which books to include for political reasons. The historical evidence does not support that narrative.
Constantine convened the Council of Nicaea in 325 AD — but that council addressed the nature of Christ (the Arian controversy), not the biblical canon. There is no reliable historical record of any vote on which books to include in the Bible at that council. The confusion between Nicaea and the formation of the canon is a widely spread historical error in popular culture, with no basis in the council's own original documents.
One especially telling piece of evidence comes from before any council: during the Diocletian persecution, in the early 4th century, Christians were arrested and killed specifically for refusing to hand over copies of Scripture to Roman authorities for burning. That martyrdom only makes sense if the books were already treated as sacred decades before any formal council "approved" them. The councils publicly recognized an authority that the persecuted church already lived out and defended with its own life.
Why Catholics, Orthodox, and Protestants Have Different Canons
Despite all this shared history, Christian traditions today don't have exactly the same Old Testament — and understanding why helps avoid common misunderstandings between believers from different churches. For anyone wanting to explore this topic more broadly, the article on Catholics vs. Evangelicals also covers other points of doctrinal disagreement beyond the canon.
Protestant Tradition — 39 OT books
Follows the Hebrew canon, the same one recognized by the Jewish people and cited by Josephus in the first century.
Catholic Tradition — 46 OT books
Includes seven deuterocanonical books, plus additions to Esther and Daniel.
Eastern Orthodox Traditions — broader canon
Some Orthodox churches also include 3-4 Maccabees, Psalm 151, and other additional writings.
An important point — often overlooked in this debate — is that this divergence only affects the Old Testament. The 27-book New Testament canon is, in practice, universal: Catholics, Orthodox, and Protestants fully agree on which books make up the New Testament, a consensus in place since the 4th century, with no significant exception in any major historic Christian tradition.
How This Strengthens Our Confidence in the Bible Today
Understanding how the canon was formed shouldn't shake confidence in the Bible — quite the opposite, it should strengthen it. The process wasn't arbitrary, rushed, or controlled by a single political power. It was a communal, gradual, and carefully verified recognition, sustained by communities of faith who, in many cases, paid with their own lives for the conviction that those specific books came from God.
This doesn't mean there are no honest questions today about the exact boundaries of the Old Testament canon among traditions — as this very article has acknowledged. But it does mean Christian confidence in the Bible doesn't rest on a legend about secret councils or arbitrary decisions: it rests on a documented historical process, open to scrutiny, and on a community that recognized — not invented — the voice of God in its Scriptures. Anyone wanting to go deeper into reading this recognized text faithfully will find a good next step in the article on how to interpret the Bible without taking verses out of context.
How the Bible Was Formed — Summary
- 📜Canon: from the Greek kanon, "ruler" — the official list of books recognized as inspired
- 📖Old Testament: 39 books, Hebrew canon already stable in the first century, per Josephus
- 🇬🇷Septuagint: Greek translation (3rd century BC) that also included apocryphal/deuterocanonical books
- ✝️New Testament: 27 books, already quoted as "Scripture" as early as the 1st century (2 Peter 3:16)
- 🔎Criteria: apostolicity, orthodoxy, and catholicity — used to recognize, not create, authority
- ⛪Councils: Hippo (393) and Carthage (397/419) ratified an already-existing consensus
- ⚖️Differences: Catholics, Orthodox, and Protestants differ only on the Old Testament, not the New
- 🙏Application: knowing this history strengthens, rather than weakens, confidence in Scripture
Continue reading about the authority of Scripture:
What Is the Inerrancy of Scripture? Definition, Biblical Basis and Objections How to Interpret the Bible Without Taking Verses Out of Context Catholics vs Evangelicals: What the Bible Says How to Read the Bible from Beginning to End Without Giving Up