The criteria for determining canonicity are difficult to determine precisely. Some books were quickly and widely received. Others appear to have been severely questioned and little used. Some books were accepted into the authoritative collection of Scripture in one locale but omitted in other places.

The most important criterion for determining canonicity is inspiration. Paul stated this principle in 2 Timothy 3:16 by suggesting that “all Scripture is given by inspiration of God.” Originally Paul’s statement referred to the inspiration of the Old Testament, but the term Scripture came to be used also in reference to New Testament writings (2 Pet. 3:16). An inference from Paul’s statement is that whatever God inspired is Scripture, and whatever God did not inspire is not Scripture. Notice that this use of the term inspiration is a precise and limited usage. The writings of a Christian teacher today might be inspiring, but we would not insist that they appear in the New Testament. When we speak of Matthew or Romans as inspired, we use the term inspired in a special sense.

How did early Christians determine the presence of inspiration? Not all New Testament books claimed inspiration. What method did the church use to demonstrate that the books in the canon deserved to be there? Three elements guided church leaders.

1. Church leaders often appealed to the agreement of the book with what they called “the rule of faith.” This meant that the teaching of the book followed the beliefs the church regarded as acceptable and correct.

2. The book had to demonstrate apostolicity. This criterion required authorship by an apostle or by the associate of an apostle (as in the instance of Mark and Luke).

3. The church applied the test of universality. This required that the book be accepted by a broad geographical segment of the church.

These three criteria can be described as orthodoxy, apostolicity, and universality.

The fact that the church accepted the present twenty-seven books as canonical does not suggest that the church created the canon or that the church caused the books to be thought of as inspired. The acceptance of these books indicates only that the church recognized their divine origin. God’s people had already sensed that these books had inherent authority. The church was ratifying what committed Christians had already accepted.

It is important to understand that early Christians produced and used many more writings than we have in our New Testament canon. The subapostolic writings were written in the period soon after the death of the apostles, and included among others, the Epistle of Barnabas, 1 and 2 Clement, the Epistles of Ignatius, and the Epistle of Polycarp to the Philippians. Among the subapostolic writings, the Didache, the Shepherd of Hermas, and 1 Clement briefly enjoyed canonical status in sections of the church. Dated somewhat later than these subapostolic writings, we also have a group of writings known collectively as the New Testament Apocrypha. These later writings included alternate gospels with such titles as The Gospel of the Hebrews, The Gospel of Peter, and The Gospel of Philip. This collection also includes legendary accounts of Jesus’ life, later acts of the apostles, and later apocalypses that are written as imitations of the Book of Revelation. The church sifted through these documents and determined that they lacked the marks of authenticity needed for inclusion in the canonical list. The fact that a document was written in ancient times did not prove that it was worthy of inclusion among the canonical writings of the period.

Christians did not use the criteria for canonicity in a mechanical fashion. Sometimes one criterion was more important than another. The opinion of a powerful church leader might also be important. These criteria, however, came to be generally adopted in the church during the period of the second century, and the church did not vary widely from them in succeeding centuries.

Lea, T. D., & Black, D. A. (2003). The New Testament: its background and message (2nd ed., pp. 71–72). Nashville, TN: Broadman & Holman Publishers.

The first Christians had none of the books of the New Testament, since the books were in the process of being written. However, they did possess the Old Testament, oral teaching about Jesus’ ministry and redemptive work (1 Cor. 15:1–4), and direct revelation from God coming through Christian prophets (Acts 21:10–14).

Evidence of the growth of the canon appears in the use of canonical writings by early Christian writers. The subapostolic writings make reference to the writings we now hold to be canonical. The use of the canonical writings in these and later documents is evidence of the acceptance of the canonical writings in various divisions of the church. This type of evidence represents the best proof available up to the end of the second century.

A second source of evidence appears in the opinions of certain writers or ecclesiastical councils.

• The Canon of Marcion, appearing in A.D. 140, provoked strong opposition among early Christians, for Marcion’s canon contained only a mutilated Gospel of Luke and ten of Paul’s epistles (excluding the Pastorals). Doubtless, the appearance of a heretical canon such as that of Marcion helped to prod Christians into naming the books they believed to be genuine.

• The Muratorian Canon, dating from A.D. 170, did not mention James, Hebrews, and the Petrine epistles, and expressed doubt about the Revelation of John, but it accepted the other New Testament writings as canonical.

• The Festal Letter of Athanasius in A.D. 367 accepted all twenty-seven New Testament writings.

• The Third Council of Carthage in A.D. 397 received the full complement of New Testament writings. After this time there was general agreement on the content of the New Testament canon.

A third source of evidence of canonicity comes from the contents of ancient manuscripts. For example, the fourth-century Codex Sinaiticus contains the entire New Testament and part of the Old in the sections that have been preserved. The New Testament portion contains the Epistle of Barnabas and the Shepherd of Hermas in addition to the twenty-seven canonical works. The contents of other ancient manuscripts provide similar evidence.

Lea, T. D., & Black, D. A. (2003). The New Testament: its background and message (2nd ed., pp. 72–73). Nashville, TN: Broadman & Holman Publishers.