Christians agree on much of the Bible, but their tables of contents differ. Understanding those differences involves history and a question about authority: how does a community recognize a writing as Scripture?
Begin with the terms
A canon is the collection received as sacred, authoritative writing. Most Protestant Bibles have 39 Old Testament books and 27 New Testament books. Catholic Bibles have 46 and 27, with longer forms of Esther and Daniel. Orthodox collections vary. Numbers alone can mislead: a tradition may count one writing as two books, or print a work in an appendix without giving it the same status.
Deuterocanonical is a Catholic name for Old Testament writings whose recognition involved historical discussion; it does not mean they are less inspired. Protestants commonly call these writings Apocrypha. Orthodox writers may use “longer canon” or other terminology. These names reflect different views of which books belong in Scripture.
The Protestant case: the Hebrew collection as the boundary
Many Protestants argue that Christians should receive the Old Testament collection associated with the Hebrew Scriptures of Judaism, while distinguishing other valuable ancient Jewish writings from Scripture. They connect this with Paul's account of Israel being entrusted with God's words in Romans 3:1–2. A church can recognize divine authority without creating it.
Michael Kruger’s The Apocrypha develops a Protestant defense using Jewish reception and differing early Christian judgments. The Westminster Confession, chapter 1, gives the Reformed standard. Its list excludes the Apocrypha from doctrinal authority. Protestant practice still varies: some editions print the additional books for reading and instruction.
The challenge: early Christian use was more varied than a single uncontested list, and Greek-speaking Christians read broader collections. Catholics and Orthodox ask why later Jewish boundaries should settle the Christian collection. The Protestant response: widespread use is evidence of importance, but does not alone establish inspiration; ancient Christian disagreement itself makes an appeal to a single uniform larger canon difficult.
The Catholic case: recognition through apostolic Tradition
Catholic teaching argues that Scripture was received within the church's continuing transmission of apostolic faith. The community that preserved and recognized the New Testament also had authority to identify the Old Testament writings it received. Catholics connect the books' use in Christian history with the church's continuing responsibility to identify and teach Scripture.
The Catholic Catechism, paragraphs 120–130, gives the list and its connection with apostolic Tradition. Dei Verbum, especially chapters 2–3, develops the authority argument behind it.
The challenge: Protestants ask whether church decisions can settle a collection whose authority must come from God, especially when early writers disagreed. The Catholic response: discernment does not manufacture inspiration. It identifies inspired books through a community Catholics believe God guides. Later formal definitions need not mean that the books were newly invented or first valued then.
The Orthodox case: Scripture within worship and Holy Tradition
Eastern Orthodox Christians emphasize the books received and read in the church's worship, especially its use of the Septuagint, the ancient Greek translation and collection of Jewish writings. Scripture belongs within Holy Tradition: the continuing life and transmission of apostolic faith. For Orthodox Christians, how the church has read and prayed with a book matters alongside its place in a printed list.
The Orthodox Church in America's Essential Orthodox Christian Beliefs, chapter 7, discusses the canon, ancient variations, and the Septuagint in detail. Greek and Slavic editions can differ in contents or placement. Ethiopian and Eritrean Orthodox Tewahedo traditions have their own broader collections; they should not be collapsed into one Eastern Orthodox number.
The challenge: variations raise the question of how a reader can know the precise boundary. The Orthodox response: a book's reception, liturgical use, and place within a particular church deserve attention; not every historical difference can be resolved by treating a single modern printed edition as the universal rule.
How to compare the arguments fairly
Ask which authority each argument treats as decisive: the Hebrew collection, the church's formal teaching, or reception within its inherited life. Then ask what evidence supports that authority. Avoid shortcuts such as “one person removed everything” or “one council invented the Bible.” Neither describes the whole history.
You can read a book without first settling its canonical status. Check which tradition your edition follows and which notes were added by its editors. When someone appeals to a disputed book, ask how its place in Scripture affects the argument. Return to What is the Christian Bible? for the larger map.
Sources & further reading
A question in the margin is a good place to begin.