The Canon of the New Testament

Here is a paragraph on the topic.

It may come as a surprise that some of the fine details of the Canon of the New Testament

were not authoritatively fixed until the Council of Trent, 16th Century, such as the passage of the Woman Taken in Adultery (which is not in the earliest manuscripts of John & seems to have floated loose from Luke) and certain single sentences in other places ...

The definitive Canon of the New Testament was not universally settled until the beginning of the Fifth Century. Certain books - Hebrews, the Apocalypse, and certain Epistles - were rejected by many Christian communities up until this time, and certain other books (The 'Shepherd' of Hermas, the Epistle of Clement to the Corinthians, and others) had been accepted in the corpus of Scripture. But in the Synod of Hippo (393) and the three Councils of Carthage in 393, 397 & 419 provided catalogues which are identical with the Catholic Canon of the present. Pope Innocent I, in 405, sent a list of the Sacred Books to Bishops Exsuperius of Toulouse, in Gaul. For the Catholic Church as a whole the content of the New Testament was now definitely fixed, and the discussion closed.

The final process of this Canon's development had been twofold:

positive, in the permanent consecration of several writings which had long hovered on the line between canonical and apocryphal; and

negative, by the definite elimination of certain privileged apocrypha that had enjoyed here and there a canonical or quasi-canonical standing. In the reception of the disputed books a growing conviction of Apostolic authorship had much to do, but the ultimate criterion had been their recognition as inspired by a great and ancient division of the Catholic Church.

Thus, like Origen, St. Jerome adduces the testimony of the ancients and ecclesiastical usage in pleading the cause of the Epistle to the Hebrews (De Viris Illustribus, lix).

† Notice that the ultimate criterion for the selection of books in the Bible was the Tradition of the Catholic Church. The Bible-only Christians are in a completely untenable position. The Bible is part of our tradition, it does not stand over and against it.