How Did the Early Church Know Which Books Belonged in the Bible?

As the number of Christian books grew, so did the need for the Catholic Church to discern which were truly authoritative, which were merely helpful, and which were positively harmful. This resulted in a process that gradually clarified which books did and didn’t count as Scripture.

The guiding principle for Christians was Jesus Christ himself, so the question became which books he would consider authoritative. Since he presented his ministry as the fulfillment of Old Testament prophecy, this meant the Old Testament was Scripture. Like most Jews, Jesus recognized a range of works beyond the Pentateuch as Scripture, but we have no record of him providing a list of them.

Christians therefore turned to Jesus’ appointed teachers—the apostles—for guidance. In their own writings, the apostles overwhelmingly used the Greek Septuagint translation of the Old Testament, so Christians naturally adopted the Septuagint. The apostles hadn’t warned Christians away from any of the Septuagint’s books, so the Christian community used the entire Septuagint tradition, which at this time had fuzzy boundaries.

Jesus made the apostles authoritative teachers in their own right, so their writings could also be recognized as Scripture, as could the writings of men the apostles trusted, allowing Peter’s companion Mark and Paul’s companion Luke to write Gospels. But there were limits to who could author Scripture, and this gift ceased with the close of the apostolic age. No new Scripture was written after this time.

All this gave the Catholic Church general principles for identifying which books could be Scripture, but it didn’t settle the question regarding which particular books belonged in the Bible.

So how did the Holy Spirit guide the Church into recognizing the canonicity of particular books?

The answer involved Tradition. When the New Testament authors originally gave their books to the Church, it was with the understanding that they were authoritative for the Faith. The evangelists, St. Paul, and the others didn’t view themselves as simply making suggestions or proposing ideas. They saw themselves as passing on authoritative teachings of the Christian faith to their congregations.

A key way this happened was through the liturgy. Since most people were illiterate and could not afford their own copies of the scriptures, they depended on hearing them read in church. In the A.D. 150s, Justin Martyr describes a typical Christian liturgy and notes it involved reading “the memoirs of the apostles or the writings of the prophets,” following which the congregation would be instructed to apply these to their lives:

On the day which is called Sunday we have a common assembly of all who live in the cities or in the outlying districts, and the memoirs of the apostles or the writings of the prophets are read, as long as there is time. Then, when the reader has finished, the president of the assembly verbally admonishes and invites all to imitate such examples of virtue. Then we all stand up together and offer up our prayers, and, as we said before, after we finish our prayers, bread and wine and water are presented. He who presides likewise offers up prayers and thanksgivings, to the best of his ability, and the people express their approval by saying “Amen.” The eucharistic elements are distributed and consumed by those present, and to those who are absent they are sent through the deacons.

The congregations received the books handed down from the apostles on the understanding that they are authoritative. They knew and trusted the New Testament authors. Indeed, they had entrusted their eternal souls to their teachings. Consequently, they accepted the New Testament books in faith and handed them on in the churches as authoritative.

A tradition was thus established that these books were the genuine article. In the case of many, the tradition spread so quickly and strongly that there was never any doubt among Christians about their status. Thus, people never doubted the inclusion of books like Matthew or Romans in the canon.

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