No single man and no single council decided the contents of the Bible. The canon took shape slowly, first through the usage of the Churches, which read certain writings and not others. Bishops such as Athanasius, and then regional councils such as Hippo in 393 and Carthage in 397 and 419, later drew up lists that reflected this usage.
Criteria forged in the face of heresies
In the second century, movements such as Gnosticism, Montanism or Marcion, who kept only part of Paul’s letters and rejected the Old Testament, forced the Church to specify which writings were authoritative. The Muratorian fragment, often dated to the late second century, is the oldest known list of New Testament books.
Four criteria emerge from this: antiquity, apostolic origin, use in the Churches and conformity with the faith received. Inspiration alone was not enough: some Fathers regarded as inspired writings that were not retained, such as the Shepherd of Hermas.
Athanasius, the councils and the emperor
In 367, Athanasius of Alexandria gave for the first time exactly our 27 books of the New Testament. His list did not prevail all at once: Gregory of Nazianzus left out Revelation, John Chrysostom several letters. Augustine acknowledged that not all books have the same authority and advised following the most numerous and most important Churches.
Politics also played a part. Diocletian’s persecutions, in 303, forced believers to choose which books to hide. Then Constantine ordered fifty copies of the Scriptures from Eusebius of Caesarea, which required their limits to be fixed. The councils of Hippo and Carthage listed the books, but they were regional: no ecumenical council of the early Church ever ratified the New Testament canon.
And the Old Testament?
The idea of a Jewish council at Jamnia, around AD 90, which supposedly closed the Jewish canon, has now been largely abandoned by historians. Among Christians, the limits of the Old Testament became a subject of conflict again in the sixteenth century: the Reformers rejected the deuterocanonical books, and the Council of Trent, which opened in 1545, confirmed them. This slow formation can be seen as a reason for doubt, or on the contrary as a reason for confidence.