What criteria were used to determine the canon of Scripture?
The doctrine of canonicity is the church's affirmation of the belief that the 66 books of the Bible comprise the only inspired books that there are. And because they are inspired, no other books are; they have a unique divine authority by which we follow in our life and belief what they teach.
How did the church come to the decision about these 66 books being the normative standard for faith and practice?
1. Written by a recognized prophet or apostle
This did not cover every book of the Bible; in fact there are some books for which we simply do not know who the author is. Hebrews is one book that took a long time for the church to recognize; now, don't have in mind that the church just decrees that now this is authoritative. But it did take longer on some books than others for the church to come to recognize as authoritative. The book of Hebrews took longer because who is the author? By a number of other criteria (which we will come to), it is clear that Hebrews is inspired; it belongs in the canon, but authorship caused it to be accepted late. But many of the books of the Bible are able to be accepted by the fact that they are written by a recognized prophet, by Isaiah, Jeremiah, Ezekiel, Moses, Paul or Peter. So there are a lot of books that are pretty clear cut because of the author.
2. Written by those associated with recognized prophet or apostle
These are books written by those associated with a recognized prophet or apostle who obviously learned from the apostle or prophet, and therefore the book is recognized really as under his supervision or teaching or instruction. The clearest case of this would be Luke and Acts. They comprise a lot of the New Testament in terms of total pages. That is a big volume of our New Testament that is not written by an apostle, but Luke traveled with Paul and learned from Paul. As he explains in Luke 1, he worked very hard to represent accurately from sources which he gathered what was true about Christ, his life, ministry, teaching, death and resurrection. So close proximately to an apostle or prophet was an important aspect.
3. Truthfulness (Deut. 18:20-22)
Truthfulness of the writing. If anything were found in a writing that was not true, it would be dismissed as not from God. God himself said in Deuteronomy 18:20-22 that if a prophet claims to be speaking from me, and what he said is not true, then he has not spoken from me. It is not from the Lord if that is the case. You can see why inerrantists are so insistent on the accuracy of the Bible. God himself goes on record. If it is from God, it has to be accurate.
4. Faithfulness to previously accepted canonical writings
This is where Hebrews shines, in terms of the Church's acceptance of it. Hebrews not only agrees with, but helps explain and bring to greater clarity, what has been taught in the Old Covenant (Old Testament); it is now seen anew in Christ and the New Covenant is so beautifully displayed.
5. Confirmed by Christ, prophet, apostle (e.g. Luke 24:44; 2 Pet. 3:16)
The whole Old Testament, although this was not convincing to Jewish scholars (to Judaism in the first century); the Christian Church has had no difficulty accepting the 39 books of the Old Testament because of what Jesus said in Luke 24:24-27,44. You will recall when Jesus met the two on the road to Emmaus and was talking with them. That is clearly a reference to the Old Testament that was used and accepted in the days of Jesus.
Now the New Testament becomes, as we have alluded to, a more difficult matter in some books. 2 Peter 3:16 is interesting. There is obviously an awareness in the first century, an apostolic awareness, that more Scripture was being written. Paul himself understands what he wrote was the Word of God. Peter, in 2 Peter 3:16, understands what Paul wrote as Scripture. Paul himself refers to his own writings with language like that. 1 Thess 2:13 For this reason, we also constantly thank God that when you received the Word of God, which you heard from us, you accepted it not as the word of men, but for what it really is, the Word of God, which also performs its work in you who believe.
6. Church Usage and Recognition
Ultimately, what happened was that these letters circulated and more and more groups of Christian people were edified by these writings and came to witness together that these writings were from God. The Church used these writings and was deeply edified by them; they were believed over time that they were from God, and so the final acceptance of the recognition of the 66 books of the Bible as Scripture took place at the Senate of Carthage in A. D. 397. That is not to say that prior to that there was not wide recognition of most of the Bible (we are talking here mostly about the New Testament; the Old Testament Books were never in question because of the dominical approval in Luke 24 when Christ says the Law, the Prophets and the Writings). Some of the New Testament books took longer for them to accept, but most of them were accepted by the first century. There were some that took longer: 2 Peter, 2 John, 3 John, Jude, Hebrews. Those took longer. But by 397, at the council of Carthage, they were accepted by the Church and have been ever since as canonical.