You might have the impression that the selection process for the books and letters that became recognized as Scripture by the early Christians was purely arbitrary. If so, you would not be alone. The truth, however, is that each of the New Testament documents was subjected to a series of tests—formally and informally—to validate their acceptance as Scripture.
1. The Authority Test.
A primary consideration when deciding if a document should be regarded as Scripture was whether or not it bore the authority of the apostles. Were the words written or sanctioned by an apostle? As described by F.F. Bruce in The Canon of Scripture, “If a writing was the work of an apostle or of someone closely associated with an apostle, it must belong to the apostolic age. Writings of later date, whatever their merit, could not be included among the apostolic or canonical books.”
For example, consider the Gospels of Matthew and John. These biographies of Jesus were written by apostles and therefore carried apostolic authority. Alternatively, the Gospels of Mark and Luke were not written by apostles but by coworkers of the apostles, giving them apostolic authority, too.
Contrast that with the Shepherd of Hermas, which was not written until sometime in the 2nd century and therefore could not have possessed apostolic authority. While it may have been treasured by Early Church Fathers such as Irenaeus and Origen, it could not be viewed as having the same authority as the canonical Gospels.
In certain cases, New Testament books acknowledged the authority of each other. Peter endorsed the writings of Paul (2 Peter 3:15-16), Jude quoted from Peter (Jude 1:17-18), and Paul quoted from Luke (1 Timothy 5:18). The result is a cross-verification among the apostles themselves, validating that the writing could be accepted as authoritative.
2. The Consistency Test.
As Christianity emerged from Judaism, the Christian Scriptures appeared as a continuation of the Jewish Scriptures. Jesus Himself claimed that He came to fulfill the Jewish laws and prophecies, not to oppose or replace them. Therefore, any New Testament book accepted as Scripture by the early Christians had to be completely consistent with the Jewish writings of the Old Testament.
As an example, consider the book of Hebrews. The identity of the author of Hebrews is uncertain, though suggested possibilities include Paul, Barnabas, Luke, Apollos, Silas, or Priscilla. The book is believed, however, to have been written in the second half of the first century, possibly before AD 70. This supports the notion that it was written with apostolic authority—or at least during the Apostolic Age—even though the author cannot be verified.
Hebrews was not accepted just because it was written within the required timeframe, however. Rather, it was accepted because it so powerfully shows how Jesus fulfilled Old Testament prophecies, laws, and rituals. The book maintains a remarkable consistency with the Jewish Scriptures.
Beyond requiring that the New Testament books be consistent with the Jewish Scriptures, the consistency test was also applied from one New Testament book to the next. For instance, with some of the letters of Paul becoming recognized as Scripture early on, later works had to be consistent with Paul’s writings. Any inconsistency would be reason to either reject the later work or reevaluate Paul’s letters.
3. The Acceptance Test.
The books and letters of the New Testament were not compiled by bishops voting at a Church Council. Indeed, the conditions of the first few centuries would have made it too dangerous for such a council to meet. With the distances involved and the looming threat of persecution or execution, it would have been impossible for representatives from across the Church to come together to determine which documents would be accepted.
Instead, there were hundreds (possibly thousands) of copies of the New Testament documents being circulated very early in the life of the Church. Believers throughout the Roman Empire and beyond were experiencing the books first-hand and were evaluating for themselves whether the books were inspired, practical, and true.
Within a generation of the end of the Apostolic Age, every New Testament book and letter had been referred to by a Church leader as being authoritative. Christians everywhere were beginning to recognize the same group of Christian writings as Scripture. Across great distances and in diverse geographic and cultural regions, the same documents repeatedly rose to the top. (Incidentally, the preponderance of manuscripts in various regions virtually eliminated the possibility of the New Testament being engineered or edited for political reasons.)
Later on, when challenged by skeptics and evaluated by official Church Councils, the accepted documents continued to find widespread support. In the face of intense scrutiny over the past two thousand years, the same texts have continually been recognized by Christians as being the authoritative Word of God.
4. The Inspiration Test.
If a work is truly Scripture, it can be expected to possess a self-evident authority that confirms its inspiration. It should “ring true” and speak powerfully to the heart of the reader, challenging and transforming the reader in the process. Admittedly more subjective than the others, this fourth criteria was vital to the acceptance of the New Testament documents 2000 years ago and remains so today.
Debates have taken place regarding some books, as not all Christians have always agreed on the inspiration of every New Testament text. Yet the vast majority of Christians at any given time have attested to the inspiration of all the accepted texts. Believers throughout the centuries have testified to the power of God working in and through the words of the New Testament books, transforming lives in the process.
The 27 books of the New Testament gelled so quickly because it was natural for them to do so. They “fit” together. The documents are consistent with each other and with the Old Testament, sharing the overarching story of the love of God displayed through the life, death, and Resurrection of Jesus.