The word in Greek means a ‘rule’ or ‘standard’ and is applied to those books in the Bible which have been recognized as authoritative, but in both OT and NT the process of finalizing the canon was gradual and controversial.

Jews agreed that the Pentateuch in its final form after the Exile was fundamental. After that, the Prophets, which included Joshua and the historical books, as well as the major and minor prophets, became accepted but not by the Samaritans. Finally, the section called the Writings (Ketubim) (consisting of eleven other books in Hebrew), was eventually settled in the 1st cent. CE, though not always in the same order. The rabbis who taught at Jamnia are regarded as having a responsibility for finalizing the collection, and what they did above all was to exclude those books which were written in Greek and were widely read amongst Greek‐speaking Jews. These came to be known as the Apocrypha. But the notion of a fixed OT canon was very loose in the 1st cent. and it is noticeable that the epistle of Jude (verses 14–16) quotes from the book of 1 Enoch as though it was scripture, although it was not accepted as canonical.

Christians, living in the Hellenistic world, naturally accepted the Greek OT, the Septuagint (LXX), as their scriptures. This contained the books excluded from the Hebrew canon such as the Wisdom of Solomon, Ecclesiasticus, 1 and 2 Maccabees; and when Jerome was translating into Latin he learnt from Jewish scholars that these were regarded as secondary (even by Hellenistic Jews). So he refused to include them in his Latin Bible. However, Jerome's view did not prevail, and, called ‘deuterocanonical’ (second‐level), they were incorporated into the Vulgate from the Old Latin version and retained their authority, as has always continued to be the doctrine of the Roman Catholic Church. At the Reformation the books of the Apocrypha were excluded by Protestants from authoritative scripture; so, when Article 6 of the Anglican Thirty‐Nine Articles declares that the OT (Hebrew books) and the NT contain all things necessary to salvation, it is asserting that these books contain the maximum number of scriptural writings that can be regarded as having authority for Anglican Christians. The books of the Apocrypha are, however, usually printed between the two Testaments and passages from them are included in lectionaries for optional use in public worship.

But the fact is that it took time also for the NT list to be finalized, and many occasional sayings of Jesus (known as agrapha) and several whole books are sometimes quoted by the early Fathers as authorities even though they are not within the final canon of twenty‐seven, for which the indisputable criteria were the insistence on the unity of God, whose created world is in principle good, and the reality of Jesus' incarnation. The main stages of the process of recognition were:

  • 1. Epistles addressed to various Churches were preserved by them, and in due course the letters of Paul formed a collection. Conceivably, this was the contribution of Onesimus; and the epistle to the Ephesians could have been an editorial introduction to the corpus, summarizing Paul's essential thoughts. Oral traditions about Jesus were constantly repeated and much valued as the ‘living tradition’ (Papias) but in due course this was cast into the written form of the four gospels, which are regularly quoted from the middle of the 2nd cent. CE onward. The adoption by Christians of the codex (book), in place of the roll, was probably an influence now on the composition of the canon. Four gospels conveniently contained in a single codex tended to sideline alternative rivals.
  • 2. The heretic Marcion, about 140 CE, issued his own NT consisting of most of Luke and ten epistles of Paul, apparently in opposition to a larger collection already circulating in the Catholic Church, though his influence has been exaggerated.
  • 3. Irenaeus, about 180 CE, quotes most of the NT books as having an authority equal to that of the OT.
  • 4. The Muratorian Fragment, probably from about 190 CE, gives a list which includes four gospels (Matthew by inference—the beginning of the document is missing) Acts, thirteen epistles of Paul, the Johannine epistles, Jude, and the Revelation, but not Hebrews, James, or 1 and 2 Peter. The Shepherd of Hermas is allowed for private reading, and it is conceded that the Church is divided about the Apocalypse of Peter.
  • 5. Clement of Alexandria (d. 215 CE) admits fourteen epistles of Paul (Hebrews is included). There is no mention of James, 2 Peter, 3 John; but he accepts the Shepherd of Hermas.
  • 6. Eusebius (d. 340 CE) has a threefold classification; he notes the accepted, the disputed, and the rejected books. His first category includes the four gospels, Acts, fourteen epistles of Paul, 1 Peter, 1 John, and (with hesitation) Revelation. In the second category, James, Jude, 2 Peter, and 2 and 3 John are regarded as widely approved, but much less so are the Didache, Acts of Paul, the Apocalypse of Peter, the Shepherd of Hermas, and the epistle of Barnabas. The totally rejected books are the gospels of Peter, Thomas, and Matthias.
  • 7. Athanasius of Alexandria wrote a letter in 367 CE giving the list of twenty‐seven NT books (and some others for private reading only) and this provides the earliest evidence of the final canon for Eastern Christendom.
  • 8. Augustine's criterion was universal acceptance and his North African Church followed Athanasius in 393. Jerome published his Vulgate in 405 and this was decisive in the West for establishing the content of the canon. But Jerome admitted the epistle to the Hebrews and Revelation reluctantly and only on the ground that they had been recognized by early Fathers.
  • 9. The Council of Carthage (397 CE) forbade non‐canonical books to be read publicly, and appended the authorized list, of twenty‐seven books.

The provision of the authorized canon was a defence of orthodox Catholicism against heresies such as Gnosticism and Montanism. Among the criteria for gaining admission to it were: authorship by or recollections of an apostle; the reliability of the witness to Jesus Christ; and wide consensus of the Churches.

At the Reformation, Martin Luther translated all the books of the OT and the NT into German, but relegated the OT Apocryphal books to an appendix—and also James, Hebrews, Jude, and Revelation (not a precedent followed by modern Lutheran Churches).