This article originally appeared in Biblical Illustrator Magazine.
The Word "canon (from the Latin, kanon) originally meant "measuring reed," but eventually developed the meaning "standard." Pertaining to the New Testament, the term refers to those books the church accepted as the standard that governs Christian belief and conduct.
Why? The need for canonicity
When the apostles were alive and operating in the first century, no great need existed for a canon to be defined. This was because the apostles were divinely appointed and ordained men who had in themselves the authority of the Lord Jesus (Matt. 10:40; 1 Cor. 9:1-2).(1)
The apostles got the church "off the ground," in a manner of speaking. They were God's authority on earth between the time of the Lord's ascension into heaven and the completion of the New Testament Scriptures, which would then become the final and continuing authority. As long as the apostles and their immediate disciples were alive, people could easily determine what constituted apostolic teaching. Certain developments, however, prompted the need for defining a canon of New Testament Scripture.
Rise of heresies
The rise of certain heresies occasioned the need for defining a New Testament canon. For example, a man named Marcion came on the scene around A.D. 144 advocating heretical views. He held to an Old Testament god who was harsh, judgmental, and vindictive, and a New Testament god who was loving, gracious, and kind. Marcion believed the New Testament god sent Jesus to redeem people from the Old Testament god. Because Marcion contended that the apostle Paul was the only preacher of the true word of God, he compiled his own Bible. He rejected the Old Testament as inferior; his "canon" consisted of the Gospel of Luke (with certain adjustments for things he did not like) and 10 of the Pauline epistles. He did not include the Pastoral Epistles or Hebrews. When Marcion and other heretics began to publish their views and establish canons themselves, the true followers of Christ necessarily had to refute them by defining what the whole church regarded as the canon.(2)
Roman persecution
During times of intermittent Roman persecution,(3) Christians were subject to imprisonment and even death if they possessed any of the Christian Scriptures. The possibility of imprisonment or death made it imperative to differentiate between which books the church would recognize as being a part of God's Word and any corollary or supplemental works.(4)
Apostles dying
As the second century wore on, the apostles' oral teaching was becoming less familiar to believers; and the apostles' disciples were beginning to die. Thus, Christians were being separated further from the apostles' authoritative teaching. This meant Christians placed less reliance on the apostles' oral teaching and more reliance on their writings and the writings of those under their supervision. Thus, the early believers recognized the need to define the canon of Scripture so later generations might know what apostolic doctrine was and was not.)5)
How? The criteria of canonicity
The basic criterion for recognizing books as being part of the New Testament is whether they were considered "God-breathed" (2 Tim. 3:16, NIV). Books do not become inspired because they are recognized as being canonical; rather, they are recognized as being canonical because they are inspired by God. Thus, the church did not "produce" the canon.
Three principal criteria seemed to emerge which the early church used in recognizing books that had been God-inspired and thus canonical:(6) apostolic origin, recognition by the church, and apostolic content.
Apostolic origin
Christ had commissioned His apostles to be His authoritative spokesmen after His ascension. Additionally, the Holy Spirit inspired and gifted these men, enabling them to write inerrant Scripture and teach inerrant doctrine. Therefore, the canonical books were to be related in some way to one of these authoritative, inspired apostles.(7) The early Christians essentially asked, "Is this particular work under question the work of one of the apostles?" Or, "If it is not the work of the apostle himself, was it produced under the supervision of and with the stamp of approval of one of the apostles?"
Jesus' apostles wrote most of the books in the New Testament.(8) For example, John and Matthew were apostles. Additionally, Paul accounts for roughly half of the books. Luke, who wrote two New Testament books, was not an apostle.(9) The early church, though, generally recognized him as Paul's protégé, advisor, traveling companion, and physician. Or consider the writer of the Gospel of Mark; although John Mark was not an apostle, early Christians generally recognized Peter as Mark's historical source.(10) These works thus meet the criterion of apostolicity.
Recognition by the churches
This principle asked how the earliest leading churches regarded the book.(11) If the churches at Ephesus, Jerusalem, Antioch, Rome, and Carthage, for example, accepted a book as authoritative, then chances were strong that the church as a whole would give it serious consideration for inclusion.
Content of the book
This criterion asked whether a particular book's content agreed with the doctrine the apostles taught orally or wrote when they were still alive. If anything was contrary to the apostles' actual teaching, it was considered spurious and not the Word of God. The early church leaders - those who had heard the apostles, or who at least had heard the immediate disciples of the apostles - recognized that as time wore on, these distinctions would become increasingly difficult to determine. This motivated them to determine and delineate the genuine New Testament canon in the earliest Christian centuries. This means the only apostolic doctrine we know today is what we get out of those written Scriptures.
So, all of this leads to what was perhaps the "prime" criterion, that being, "Was this book produced by an apostle or under the auspices of an apostle, and does it obviously correspond to the doctrine the apostles themselves taught when they were on earth as God's divinely appointed spokesmen?"
An example of this criterion at work is the Gospel of Thomas, a book that did not attain canonical status. This writing bears the name of an apostle, but it is not in accord with what the apostles taught. The book for many years was clearly recognized as a Gnostic-based forgery espousing the heresy of Gnosticism. The fact that it bears an apostle's name does not mean that it was apostolic; its content does not agree with apostolic doctrine.
When? The pivotal dates
What were the pivotal dates for the recognition and formal establishment of the New Testament canon? In the eastern church the 39th Paschal Letter of Athanasius, the Bishop of Alexandria, dates to A.D. 367. This document was the bishop's letter to the faithful written on the occasion of Passover. In this letter Athanasius mentions 27 books the church accepted as being the New Testament. In the western church the Council of Carthage met in A.D. 397. Part of the council's work was to publish the names of the 27 books that the church held to be genuine Scripture. Putting these two dates together makes evident that by the middle-to-late fourth century the church had no question about the 27 books that would comprise the New Testament. No really serious question has risen since.
Not all the books that the apostles wrote became Scripture. For example, Paul wrote four letters to the Corinthians, two of which are lost and thus not in the canon (1 Cor. 5:9; 2 Cor. 7:8). Nonetheless, the New Testament we possess today can be trusted.
Jesus, while on earth, did not specifically mention writings that would become what we know as the New Testament. He did seem to "pre-authenticate" the New Testament, however, when He told His disciples: "These things I have spoken to you while abiding with you. But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all that I said to you" (John 14:25-26, writer's translation).
The prophets of old spoke "as they were moved by the Holy Spirit" (2 Pet. 1:21, HCSB). We can affirm with confidence that those who penned the New Testament wrote in like manner. Their work is God's inerrant Word, entirely true, and the result of His sovereign oversight and provision. By God's grace and providence, the early church recognized those books that God inspired to be included in the New Testament canon.