We’ll deal with both of these questions in turn:
How did the NT canon become established?
As each new part of the New Testament (NT) scriptures was written it would have become accepted by the Christian community because it was written by people they knew were authoritative.1 In this way the traditional canon of NT Scripture was built up as each new section of the NT was written.
It was only after the death of the last of the apostles, and in the face of developing false teachings, that the church felt the need to draw up a canonical list of what was regarded as scripture.2
Did the church decide what books the canon should include?
Bearing the above in mind, it is not a case of the church deciding what books should be in the canon. Rather, the church recognised which books were scripture. As Carson, Moo and Morris put it:
The church’s role is not to establish what books constitute scripture. Rather, the scriptural books make their own way by widespread usage and authority, and the church’s role is to recognize that only certain books command the church’s allegiance and obedience, and not others — and this has the effect of constituting a canon, a closed list of authoritative scripture.
Because the canon is made up of books whose authority ultimately springs from God’s gracious self-revelation, it is better to speak of recognizing the canon than of establishing it.3
The church followed the injunction to ‘test’ (1Thess.5:20-21; 1John4:1) which messages were from God, and which weren’t. By doing this they recognised which books where really scripture, and which books weren’t.
We know from extra-biblical writings that the bulk of what we call the New Testament was already firmly recognised during the second century A.D., with discussions about a few of the other books.4 The process of reaching a complete list would, understandably, take some time as people “tested” the (limited) books available to them,5 hampered further by the ‘slow and precarious’ nature of communication in those days.6 However, ultimately the church, through testing and dialogue, recognised that the 27 books, and only those books, that make up the NT were scripture.7
1. Additionally, certain of the Christians in the first century A.D. had the miraculous ‘ability to distinguish between spirits’ (1Cor.12:10) to tell what was really from God and what wasn’t (cf. 1Thess.5:20-21; 1John4:1).
2. B. F. Westcott, A General Survey of the History of the Canon of the New Testament, 5th edn (London: Macmillan & co, 1881), p. 5-6
3. D. A. Carson, Douglas J. Moo, and Leon Morris, An Introduction to the New Testament (Zondervan, 1992), p. 498,499
4. See, for example, the Muratorian canon (c. 170: overtly recognising 22 of the 27 NT books), the writings of Irenaeus (b. 130: overtly recognising 21 of the NT books — see under T in this table) and the Diatessaron (c. 170: a harmony of the four Gospels, Matthew, Mark, Luke and John).
5. The process would have been quicker had the Holy Spirit gifts still been available (see Note 1); however, by this time in the early church the Holy Spirit gifts had passed away (the church’s slow progress over the process of recognising the canon is, in fact, another extra-biblical evidence that the Holy Spirit gifts ceased early in the history of Christianity. See ‘Have the Holy Spirit gifts died out?‘ for more information).
6. B. F. Westcott, A General Survey of the History of the Canon of the New Testament, 5th edn (London: Macmillan & co, 1881), p. 4-5
7. ibid, p. 5