How did the early church decide which books to include in the New Testament?
The inspiration of Scripture is connected to the canon. We might make the case that the New Testament is inspired by God. We see God’s fingerprints on it, but exactly what books would fall into that category? How were the New Testament books chosen as part of the canon? This was a complicated process in some ways, but there are some general guidelines that drove the process.
A bunch of people who had authority in themselves did not get together and just pick the ones that they said were the right New Testament books. The books did not have authority in virtue of who chose them. That's not the way it worked.
The word "canon" means authority. That is, what are the authoritative works in themselves in the New Testament era that tell us about God and His plan for salvation? Before they were books for the New Testament, what was the canon?
Jesus trained 12 people (and more if you consider Paul after the cross) to take His message, and promised them in the upper room discourse in John 15 that He would bring to remembrance all the things that He had taught them so they would be able to communicate to others. Because of their close association with Jesus, this group of men became the standard, or the canon.
The early church looked to the apostles for the authoritative word about what was sound doctrinally. What happened when the apostles died? Was there a whole new generation of apostles that had the same authority? There’s no biblical evidence for that. Although the apostles were gone, their writings still remained in the early church. The things that they instructed us regarding are still here. Those things are the authority now that those men are no longer alive.
The central question with regards to the canon was: Does any particular book bear with it apostolic authority? Did a bona fide apostle who had authority write it, and therefore the authority would be in his word? Or was the book written by someone associated with a bona fide apostle close enough that it gives authority to his work? Luke would be an example of somebody associated with the apostle Paul. Mark would be associated with the apostle Peter, and therefore would have authority in that regard. You have others that were very tightly connected to the apostolic band like Jude, for example. James was clearly an apostle and the half-brother of Jesus, a leader of the early church. Consequently, these books had authority in themselves because of their authorship.
The early church didn’t just assemble a collection of books. Rather, there already was a collection of books that virtually everybody agreed had authority. There are a couple exceptions – 2 Peter, Revelation, and Hebrews – partly because they weren't exactly sure who wrote Hebrews, but this was something that they worked out.
The point that I want to leave with you is it's not a haphazard affair. It wasn't just a matter a voting by a bunch of people who saw themselves as the authority. Rather, it was an act of Christian leaders who recognized the authority inherent in those books principally because of the apostolic connection that those books had. That is the foundational way in which the New Testament documents were viewed as authoritative and part of the canon.