How Do We Know Which Books Belong in the Bible?
Short Answer
We know which books belong in the Bible because the books of Sacred Scripture were inspired by God and entrusted to the Church, and the Church, guided in preserving the deposit of faith, gradually recognised, received and ultimately defined which writings belong to the canon of Scripture.
This distinction is essential. The Catholic Church did not make Matthew, Romans, Hebrews or Tobias inspired. A book is inspired because the Holy Ghost is its divine author. The Church's authority does not create inspiration; rather, it enables the faithful to know with certainty which books God actually inspired. The First Vatican Council expressed this precisely: the books are sacred and canonical because, having been written under the inspiration of the Holy Ghost, they “have God as their author” and were entrusted as such to the Church.
The historical evidence is important because there was no universally agreed, complete table of contents handed to Christians on the day of Pentecost. Some books were accepted almost everywhere from very early times; others were disputed for centuries. Hebrews, James, 2 Peter, 2 and 3 John, Jude and the Apocalypse were among the New Testament books whose reception varied. In the Old Testament, Tobias, Judith, Wisdom, Ecclesiasticus, Baruch, the Machabees and portions of Esther and Daniel were disputed in various places. At the same time, respected writings such as the Shepherd of Hermas, the Didache, the Epistle of Barnabas and the Apocalypse of Peter were sometimes read and highly esteemed but were ultimately excluded from the biblical canon.
The canon therefore provides a concrete historical example of why Christianity cannot be reduced to “the Bible alone.” Before a Christian can appeal to “the Bible,” he must first know which books constitute the Bible. Scripture itself does not contain an inspired table of contents identifying all its books. The answer was preserved and settled within the life, Tradition and authority of the Catholic Church.
Why This Question Matters
Every Christian doctrine argued from Scripture presupposes a more basic question: which writings are Scripture?
A Protestant and a Catholic can agree that “all scripture, inspired of God, is profitable to teach” in 2 Timothy 3:16–17
But this passage does not tell Timothy whether Hebrews is inspired, whether the Apocalypse belongs in the New Testament, whether the Shepherd of Hermas should be included, or whether Tobias and Machabees belong in the Old Testament.
Similarly, 2 Peter 3:15–16 already places writings of St Paul alongside “the other scriptures,” showing that apostolic writings were recognised as Scripture during the apostolic period itself. Yet the passage does not provide a complete list of Paul's authentic epistles, much less a catalogue of all Old and New Testament books.
This is not a minor academic problem. If the Epistle of James is not Scripture, its teaching cannot be invoked as inspired revelation. If Machabees is not Scripture, its testimony concerning prayer for the dead has a fundamentally different authority. If the Gospel of Thomas were inspired, Christianity would have to receive it. The boundary of the canon determines what Christians acknowledge as the written Word of God.
The canon question therefore leads naturally to the companion articles
Why Isn't the Bible Alone Sufficient as the Rule of Faith?,
What Are Sacred Scripture and Sacred Tradition?, and
What Authority Did Christ Give to His Church?
What the Catholic Church Teaches
Inspiration Comes from God
The first principle is that God, not the Church, makes Scripture inspired.
The First Vatican Council (1869–1870), in the Dogmatic Constitution Dei Filius of 24 April 1870, taught that the canonical books were not made Scripture merely because the Church subsequently approved human writings. Rather, because they were written under divine inspiration, they have God as their author and “were as such committed to the Church.” This prevents a common misunderstanding of the Catholic position.
The reasoning is not:
The Church chose certain books, therefore those books became inspired.
It is:
God inspired certain books; Christ established a Church charged with preserving His revelation; that Church recognised, guarded and authoritatively identified the books entrusted to her.
The difference between the ontological question—What makes a book inspired?—and the epistemological question—How can we know which books are inspired?—is fundamental.
God answers the first. The teaching Church is central to the second.
The Canon Is Part of the Deposit Handed Down to the Church
The Council of Trent (1545–1563), Session IV, 8 April 1546, taught that supernatural revelation comes to the Church through the written books and the apostolic traditions handed down from Christ and the Apostles. It then deliberately gave a catalogue of the biblical books “lest a doubt may arise” concerning which books were received.
Trent did not claim to manufacture Scripture. It received the books in continuity with the Church's preceding Tradition, liturgy, councils and papal judgments. First Vatican I later reaffirmed both the Tridentine canon and its divine inspiration.
Scripture Itself Points to an Authoritative Church
The complete doctrine of the Church's teaching authority is treated elsewhere, but the principle is relevant here.
St Paul calls the Church of the living God “the pillar and ground of the truth” in 1 Timothy 3:15.
Christ commands that the obstinate offender finally be brought before “the church” and immediately speaks of the power of binding and loosing in Matthew 18:17–18.
He tells His authorised messengers:
“He that heareth you, heareth me” Luke 10:16.
These passages do not constitute an inspired table of contents. Rather, they establish the broader ecclesial setting within which revelation was preached, transmitted, preserved and recognised.
How the Biblical Canon Formed
The word canon came to mean the recognised collection or catalogue of inspired books.
Catholic theology traditionally distinguishes between protocanonical and deuterocanonical writings. This does not mean that the latter possess a lower degree of inspiration. It refers principally to differences in the history of their universal recognition: the deuterocanonical books encountered more prolonged questioning before their status was definitively settled.
A Large Core Was Recognised Very Early
Canon formation did not begin with a completely blank slate. The four Gospels, Acts, most Pauline epistles, 1 Peter and 1 John enjoyed widespread early reception. By the late second century, St Irenaeus of Lyons (c. AD 130–202) could argue in Against Heresies (c. AD 180), III.11.8, that the Church possesses four Gospels and no more. His theological symbolism for the number four is not itself proof of canonicity, but his argument is strong historical evidence that Matthew, Mark, Luke and John already constituted a recognised fourfold Gospel collection.
Irenaeus therefore witnesses not merely to isolated Christian books, but to an already established ecclesial reception of a defined group of Gospel writings. Yet agreement about the central books did not mean that every boundary had already been universally settled.
Some New Testament Books Were Genuinely Disputed
Eusebius of Caesarea (c. AD 260–339) gives one of the clearest early descriptions in his Ecclesiastical History (c. AD 325), III.25.
He distinguishes books widely acknowledged from writings whose standing remained disputed. Among writings recognised by many but still contested he names:
| Later canonical book | Evidence of early dispute |
|---|---|
| James | Listed by Eusebius among disputed writings. |
| Jude | Disputed but known and received by many. |
| 2 Peter | Its apostolic reception was questioned. |
| 2 John | Not universally received. |
| 3 John | Not universally received. |
| Apocalypse | Accepted in some places and rejected or questioned in others. |
| Hebrews | Its authorship and reception were especially disputed in parts of the West. |
Eusebius also knew Christian writings such as the Shepherd of Hermas, Epistle of Barnabas, Didache, Acts of Paul and Apocalypse of Peter. These enjoyed varying degrees of respect and circulation but did not ultimately enter the Catholic canon.
This historical fact matters greatly.
If every inspired book had been self-evidently canonical to every sincere Christian simply from its contents, it is difficult to explain why ancient churches which shared the same faith could differ for substantial periods over Hebrews, James, 2 Peter or Revelation—or why some highly orthodox writings could approach the canonical boundary without entering it.
St Athanasius and the Twenty-Seven-Book New Testament
St Athanasius of Alexandria (c. AD 296–373) provides an especially important milestone. In his Thirty-Ninth Festal Letter of AD 367, he names precisely the twenty-seven books now contained in the Catholic New Testament: the four Gospels, Acts, seven Catholic Epistles, fourteen Pauline epistles including Hebrews, and the Apocalypse. This is an important witness to the maturing consensus.
Yet Athanasius simultaneously illustrates why canon history cannot be reduced to the opinion of a single Father. His Old Testament enumeration differs in certain respects from the later Tridentine catalogue. He includes Baruch with Jeremiah but places Wisdom, Ecclesiasticus, Judith and Tobias among books appointed for reading rather than within his strict canon.
Athanasius is a Father and Doctor of immense authority. He is not, however, individually the infallible Magisterium.
St Augustine Appeals to the Judgment of the Churches
St Augustine of Hippo (AD 354–430) gives perhaps the clearest patristic description of the ecclesial method of discerning canonical Scripture.
In On Christian Doctrine (c. AD 397), II.8.12, Augustine tells the biblical interpreter to consider the judgment of the Catholic churches, giving particular weight to churches of apostolic authority. Where reception differs, the broader and weightier ecclesial testimony is to be considered.
This is striking. Augustine does not tell every Christian to examine a book privately and wait for an interior sensation identifying divine inspiration. He points to the reception and authority of the Catholic churches.
He then gives an Old and New Testament catalogue containing Tobias, Judith, the two Machabees, Wisdom and Ecclesiasticus together with the full twenty-seven-book New Testament.
Augustine therefore witnesses both to the Catholic canon itself and to the ecclesiastical principle by which disputed books were evaluated.
St Jerome Shows That Individual Fathers Could Differ
The historical evidence must not be artificially simplified.
St Jerome (c. AD 347–420), the great biblical scholar responsible for much of the Latin Vulgate, preferred what he understood as the Hebrew Old Testament canon. In his Prologue to the Books of Kings, often called the Helmeted Prologue, he placed Wisdom, Ecclesiasticus, Tobias and Judith outside his strict canonical reckoning.
This is a genuine historical difficulty for anyone who imagines that every Father always held precisely the later formally defined Catholic canon. But it is not a difficulty for the Catholic principle itself.
Jerome was an extraordinarily learned Father and Doctor, but his personal scholarly judgment was not a definition of the Church. Other Fathers—notably Augustine—took a different position. Liturgical usage, African councils and Roman authority continued to receive the books Jerome questioned. Pre-Vatican II Catholic scholarship frankly acknowledged that Jerome's influence produced continuing academic hesitation concerning some Old Testament books during the Middle Ages even while ecclesiastical usage retained them.
The disagreement among Fathers therefore demonstrates why the final question cannot be reduced to:
“Which Father can I quote?”
The question must ultimately be:
What did the Church herself authoritatively receive and define?
Councils, Popes and the Settlement of the Canon
Canon formation occurred gradually. The following stages should not be confused with one another.
Hippo and Carthage
Regional African councils played an important role. The Synod of Hippo in AD 393 and councils of Carthage in the late fourth and early fifth centuries adopted lists corresponding substantially to the later Catholic canon. The surviving African Code promulgated at the Council of Carthage in AD 419 states that nothing besides the canonical Scriptures is to be read in church as divine Scripture and enumerates Tobias, Judith, the two Machabees and the complete twenty-seven-book New Testament.
These were regional councils, not ecumenical councils. They did not by themselves constitute a solemn universal dogmatic definition.
Their importance is historical: they demonstrate what major portions of the Catholic episcopate were receiving as Scripture centuries before the Reformation.
Pope Innocent I
In AD 405 Pope Innocent I (r. 401–417) answered Bishop Exsuperius of Toulouse concerning the books received into the canon.
His list contains Tobias, Judith, two books of Machabees and the complete New Testament, including Hebrews, James, 2 Peter, 2 and 3 John, Jude and the Apocalypse.
This is particularly significant because it constitutes Roman papal testimony to substantially the same canon later promulgated at Trent more than eleven centuries afterwards.
A Caution Concerning the Council of Rome of 382
Many Catholic apologetic presentations state simply that Pope Damasus I settled the canon at a Council of Rome in AD 382.
That statement requires qualification. A canon list identical or substantially identical to the later Catholic list is traditionally attributed to Damasus and the Roman synod. However, the surviving list is transmitted within the Decretum Gelasianum, whose textual history is complex, and scholars have disagreed over how confidently the canon section can be attributed to the synod of 382 itself. Older Catholic scholarship defended its Damasan attribution, while modern textual scholarship has raised substantial questions.
Nothing essential to the Catholic argument depends upon resolving this historical question. Hippo, Carthage, Innocent I, Augustine, Florence and Trent provide independent evidence. This is a useful example of the distinction between Catholic doctrine and a disputed historical attribution.
The Council of Florence
Long before the Protestant Reformation, the Ecumenical Council of Florence (1438–1445) supplied another major landmark.
In Pope Eugene IV's Cantate Domino, the Decree for the Jacobites promulgated in 1442, the Church enumerated the books she received and venerated, including Tobias, Judith, Wisdom, Ecclesiasticus, Baruch and the two Machabees together with the full New Testament.
This fact is important because it disproves the claim that the Catholic Church first introduced these books in reaction to Martin Luther. Florence's enumeration preceded Luther's revolt by approximately three quarters of a century.
The Council of Trent
The Protestant controversy made a solemn settlement necessary. At Session IV of the Council of Trent, 8 April 1546, the Church expressly catalogued the books of both Testaments and declared that they were to be received “as sacred and canonical,” including all their parts as traditionally read in the Church and contained in the ancient Latin Vulgate.
Trent's decree includes Tobias, Judith, Wisdom, Ecclesiasticus, Baruch, 1 and 2 Machabees, the traditional portions of Esther and Daniel, and all twenty-seven books of the New Testament.
At this point the matter was no longer an open theological or historical question for Catholics.
The First Vatican Council (1870) reaffirmed Trent and attached an anathema to denial of the canonical and divinely inspired character of the complete books and their parts enumerated there.
Did the Council of Trent Add Books to the Bible?
No. That claim confuses formal dogmatic definition with the beginning of belief.
Catholics were using Tobias, Judith, Wisdom, Ecclesiasticus and the Machabees many centuries before Trent. Augustine treated them as canonical. African councils included them. Innocent I listed them in AD 405. Florence enumerated them in 1442. Medieval Vulgate manuscripts normally contained them, and they were read within the ecclesiastical life of Western Christianity.
What is true is that some Fathers and medieval theologians questioned the status of particular deuterocanonical books. Jerome is the best-known example.
Catholic history does not need this fact concealed.
Solemn definitions frequently occur precisely because earlier discussion or later controversy has made clarification necessary. The definition of AD 1546 did not mean that the Church had no Bible in AD 500 any more than the definition of Christ's two natures at Chalcedon in AD 451 means Christians had no belief about Christ before Chalcedon.
The Council settled with final doctrinal authority a boundary whose central contents had been recognised from antiquity but whose edges had experienced genuine historical dispute.
Why Church Authority Is Necessary to the Canon Question
The history gives us several facts that must be held together.
First, many biblical books bear strong internal and historical evidence of apostolic authority. Christianity did not arbitrarily choose writings from a pile of indistinguishable documents.
Second, apostolic origin or association, doctrinal orthodoxy, liturgical usage, antiquity and widespread reception all played important roles in discernment.
Third, none of these functions as a mechanically self-applying inspired test.
Hebrews does not name its human author. 2 Peter was questioned partly because of doubts concerning authorship. The Shepherd of Hermas was orthodox and widely esteemed but not apostolic Scripture. Revelation was certainly ancient yet remained disputed in substantial portions of the East. Some Old Testament books were received differently depending upon whether emphasis fell upon Greek Christian usage or a narrower Hebrew collection.
The Church had to distinguish among them. This does not place the Church above the Word of God. The Church is subject to revelation. She has no authority to turn an uninspired book into the Word of God or to remove an inspired book God entrusted to her.
Rather, it means that the same divine providence which inspired Scripture also preserved the Church in recognising the revelation committed to her.
The Main Objection
A strong Protestant objection can be stated as follows:
Scripture receives its authority from God, not from the Church. Inspired Scripture possesses divine qualities by which God's people recognise it, while the Holy Ghost bears witness in the believer's heart. The Church can testify to the canon but cannot infallibly determine it, because that would place the Church above Scripture.
This is not a caricature. The Westminster Confession of Faith (1647) states that Scripture's authority depends not upon the testimony of man or Church but upon God its author. It acknowledges that the Church's testimony can move Christians to esteem Scripture, while grounding final certainty in the internal work of the Holy Spirit.
John Calvin similarly insisted in his Institutes of the Christian Religion, I.7, that the Church does not confer divine authority upon Scripture.
That first proposition is actually compatible with Catholic doctrine.
Response
The disagreement concerns what follows from it. Catholic doctrine also denies that the Church creates Scripture's divine authority. Vatican I explicitly rejects that notion. Scripture possesses divine authority because God is its author.
But this still leaves another question unanswered:
How does the Christian know with divine certainty which particular books God inspired?
Saying that inspired books are self-authenticating does not adequately explain the historical evidence. Christians who revered Scripture and professed the same basic apostolic faith nevertheless disputed Hebrews, James, 2 Peter, Jude and Revelation. Some accepted books later excluded; others questioned books later universally received.
Nor does an internal testimony of the Spirit provide an objective public canon capable of binding the entire Church unless one already knows how authentic divine testimony is distinguished from sincere private conviction.
Augustine's approach was markedly ecclesial: consult the reception of the Catholic churches and especially churches possessing apostolic authority. The Catholic position therefore avoids both extremes.
It does not say:
“A book is inspired because churchmen voted for it.”
Neither does it say:
“Every individual Christian can infallibly recognise every inspired book directly for himself.”
It says that God inspired definite writings, committed revelation to His Church, and providentially brought the Church to an authoritative recognition of those writings.
This explains both the divine origin of Scripture and the historical process by which the canon became universally certain.
Common Objections
“But St Jerome Rejected the Deuterocanonical Books”
Jerome certainly questioned the canonical status of several of them, and his testimony should not be obscured. But Jerome was one Father, not the whole Church.
Augustine disagreed. African councils disagreed. Roman ecclesiastical practice disagreed. Innocent I's list included the books. Florence later received them, and Trent finally settled the question.
Using Jerome's opinion to override the subsequent judgment of the Church would therefore require treating one Father's biblical scholarship as possessing greater doctrinal authority than the Church whose Father and Doctor he was.
The patristic evidence matters enormously, but no single Father is individually infallible.
“If the Canon Was Not Defined Until Trent, Catholics Could Not Have Known the Bible Before 1546”
This confuses knowledge and ecclesiastical reception with a final dogmatic definition.
The four Gospels were firmly established extraordinarily early. Much of the New Testament was universally acknowledged long before Nicaea. By the late fourth century the full twenty-seven-book New Testament appears in Athanasius, Augustine and major ecclesiastical lists. The traditional Old Testament was embedded in Christian liturgical and manuscript usage even while some scholars debated the precise standing of certain books.
A solemn definition becomes necessary principally when serious controversy requires the Church to close a previously disputable question.
Trent therefore represents the definitive settlement of the canon, not the historical invention of the Bible.
“Wasn't the Canon Decided at the Council of Nicaea?”
No reliable evidence shows that the Council of Nicaea in AD 325 determined the biblical canon. The history of the disputed books after Nicaea itself makes such a claim implausible, and surviving conciliar evidence does not record such a canonical decree. Pre-Vatican II Catholic scholarship likewise distinguished the later fourth-century canon discussions from Nicaea.
What We Can and Cannot Conclude
Established Catholic doctrine: The books enumerated by the Council of Trent, complete with their canonical parts, are divinely inspired Sacred Scripture. Their inspiration comes from God, not from a later human act of approval. They were entrusted as inspired books to the Church. Vatican I definitively reaffirmed these principles.
Established historical fact: The biblical canon developed in its explicit, universally recognised form over time. A substantial central body of Scripture was accepted very early, while certain Old and New Testament books experienced genuine periods of dispute.
Established historical fact: Fathers did not always agree on every disputed book. Athanasius, Augustine and Jerome provide particularly clear examples of differing Old Testament enumerations or classifications. Eusebius records continuing disputes concerning several New Testament books.
Established historical fact: Regional councils at Hippo and Carthage, Pope Innocent I, the Council of Florence and finally the Council of Trent all form identifiable stages in the history of the Catholic canon.
Theological conclusion: The historical canon problem strongly supports the necessity of an authoritative ecclesiastical witness capable of settling questions concerning the contents of revelation. This conclusion coheres with the Catholic doctrine of the Church's teaching authority, although the complete proof of that authority rests upon the broader evidence treated in the dedicated articles on the Church and Sacred Tradition.
Disputed historical question: The precise documentary relationship between the canon list traditionally associated with Pope Damasus and the Roman synod of AD 382 and the later Decretum Gelasianum remains debated. Catholic belief in the canon does not depend upon resolving that attribution.
Disputed historical question: The date of the Muratorian Fragment has also been debated by modern scholars. Its traditional late-second-century dating remains influential, while some scholarship has argued for a later date. The Catholic case does not depend upon fixing its date.
What we cannot conclude: We cannot say that every Father always possessed an identical explicit canon, that the councils “made” uninspired books inspired, that Trent invented the deuterocanonical books, or that a single fourth-century council instantly ended all discussion everywhere.
The real history is more complicated—and more instructive.
Conclusion
The Bible did not descend from heaven as a bound volume containing an inspired table of contents. God inspired particular writings through human authors. The apostolic Church received those writings within a living body of revelation, worship and teaching. Some books were recognised almost universally from very early times; others were questioned in particular regions. Some highly respected Christian writings approached the boundary of Scripture but were ultimately excluded.
The Early Church therefore had to distinguish apostolic Scripture from merely ecclesiastical literature, authentic revelation from apocrypha, and inspired writings from books that were holy and useful without being inspired.
The Fathers provide indispensable evidence, but they sometimes differed. Regional councils helped clarify ecclesiastical reception. Roman judgments strengthened that reception. Florence enumerated the traditional books before the Protestant Reformation. Trent finally defined the canon when controversy made a solemn decision necessary. Vatican I reaffirmed both the canon and the reason for its authority: these books have God as their author because they were written under the inspiration of the Holy Ghost and were entrusted as such to the Church.
The answer to “How do we know which books belong in the Bible?” is therefore not that the Church invented the Bible, nor that every Christian independently discovers the canon for himself.
God gave the Scriptures; the Catholic Church received, preserved, recognised and authoritatively identified them.
That historical fact leads directly to the next question: if the very contents of Scripture are known through the Church's Tradition and authority, can Scripture reasonably be separated from the Church and made the sole independent rule by which the Church herself must be judged?
That question is examined in Why Isn't the Bible Alone Sufficient as the Rule of Faith?
Primary Sources
Sacred Scripture: 1 Timothy 3:15
Sacred Scripture: 2 Timothy 3:14–17
Sacred Scripture: 2 Peter 3:15–16
St Irenaeus of Lyons (c. AD 130–202), Against Heresies (c. AD 180), III.11, especially III.11.8, on the fourfold Gospel. Against Heresies III.11
Eusebius of Caesarea (c. AD 260–339), Ecclesiastical History (c. AD 325), III.25, distinguishing acknowledged, disputed and rejected writings. Ecclesiastical History III.25
St Athanasius of Alexandria (c. AD 296–373), Thirty-Ninth Festal Letter (AD 367), §§3–7. Festal Letter 39
St Augustine of Hippo (AD 354–430), On Christian Doctrine, II.8.12–13, on the judgment of the Catholic churches and the canonical books. On Christian Doctrine II.8
St Jerome (c. AD 347–420), Prologue to the Books of Kings (Prologus Galeatus), on his Hebrew-canon preference. Jerome's Prologue to Kings
Council of Carthage (AD 419), Canon 24 of the African Code, listing the canonical books. Council of Carthage, Canon 24
Pope Innocent I, Letter to Exsuperius of Toulouse (AD 405), ch. 7, §13, catalogue of canonical books. Letter of Innocent I to Exsuperius
Council of Florence / Pope Eugene IV, Cantate Domino, Decree for the Jacobites, 4 February 1442, containing the biblical catalogue. Cantate Domino — Vatican text
Council of Trent, Session IV, Decree Concerning the Canonical Scriptures, 8 April 1546. Council of Trent, Session IV
First Vatican Council, Dogmatic Constitution Dei Filius, 24 April 1870, ch. 2 and Canon 2.4. Dei Filius — official Vatican Latin text
Further Reading
George J. Reid, “Canon of the Old Testament,” The Catholic Encyclopedia, vol. 3 (New York: Robert Appleton Company, 1908). A useful pre-Vatican II Catholic survey that does not conceal the historical disputes over the deuterocanonical books. Canon of the Old Testament
George J. Reid, “Canon of the New Testament,” The Catholic Encyclopedia, vol. 3 (1908). Detailed treatment of the New Testament antilegomena and the gradual fixation of the canon. Canon of the New Testament
A. J. Maas, “Scripture,” The Catholic Encyclopedia, explaining the traditional distinction between protocanonical and deuterocanonical books. Scripture — Catholic Encyclopedia
J. P. Kirsch, “Muratorian Canon,” The Catholic Encyclopedia, vol. 10 (1911), for the traditional account of the Muratorian Fragment. Muratorian Canon
Related Questions
Why Believe the Bible Is the Word of God?
Why Isn't the Bible Alone Sufficient as the Rule of Faith?
What Are Sacred Scripture and Sacred Tradition?
What Authority Did Christ Give to His Church?
What Is Apostolic Succession, and Why Does It Matter?
Did Christ Intend Christians to Belong to One Visible Church?