Nick asked: The $64 million question is: how do you know these inspired oral teachings were eventually enscripturated?
In his work, "Scripture and Tradition," (c) 1956, Oscar Cullman noted that something like this was precisely the Roman Catholic response to his 1953 work, “Peter: Disciple, Apostle, Martyr”.
One argument especially is brought forward: scripture, a collection of books, is not sufficient to actualize for us the divine revelation granted to the apostles. (Oscar Cullmann, “The Early Church,” London: SCM Press LTD., pg 57.Some things don’t change.
Fortunately, Cullmann had the background and resources in his day to research the issues and to think it through. One of the things that I’m most excited about in reading Kostenberger and Kruger’s “The Heresy of Orthodoxy” is that they make essentially the same argument, and relate essentially the same facts.
I’m not sure why this work hasn’t been picked up by more Protestants. Cullmann puts forth this argument:
1. For Paul, the paradosis (“oral tradition”), in so far as it refers to the confession of faith and to the words and deeds of Jesus, has a parallel in the Jewish concept of paradosis.
2. This tradition relates to the direct apokalypsis of the Lord to the Apostles. That is, the office of the Apostles was unique because they provided unique eyewitness testimony to the life of Christ.
3. This tradition lived and died with the apostolic office. No other source had the eyewitness authority of the Apostles.
4. The development of the canon was a conscious decision on the part of the earliest church, born from the consciousness of the heresies spinning out of control, to establish a superior written norm, and to stake out the boundaries of orthodoxy and heresy.
Essentially, he says, the early church made a key distinction between “apostolic tradition,” that is, what the Apostles taught orally and in writing, and “post-apostolic” or “ecclesiastical” tradition.
This is the place to speak about the establishment of the canon by the Church of the second century. This again is an event of capital importance for the history of salvation. We are in complete agreement with Catholic theology in its insistence on the fact that the Church itself made the canon. We even find in this fact the supreme argument for our demonstration. The fixing of the Christian canon of scripture means that the Church itself, at a given time, traced a clear and definite line of demarcation between the period of the apostles and that of the Church, between the time of foundation and that of construction, between the apostolic community and the Church of the bishops, in other words, between apostolic and ecclesiastical tradition. Otherwise, the formation of the canon would be meaningless.[It's important to note here that, while Cullman capitalizes the word "church," he uses the word in the proper sense; not in the sense that Roman Catholics use the word.]
We must recall the situation that led the Church to conceive the idea of a canon. About the year 150 there is still an oral tradition. We know this from Papias, who wrote an exposition of the words of Jesus. He tells us himself that he used as a basis the viva vox and that he attached more importance to it than to the writings. But him we have not only this declaration of principle; for he has left us some examples of the oral tradition as he found it, and these examples show us well that we ought to think of an oral tradition about the year 150! It is entirely legendary in character. This is clear from the story that Papias reports about Joseph Barsabbas, the unsuccessful candidate, according to Acts 1/23 f., for the post of twelfth disciple rendered vacant by Judas’s treason. Above all there is the obscene and completely legendary account [in Papias] of death of Judas Iscariot himself.
The period about 150 is, on the one hand, relatively near to the apostolic age, but on the other hand, it is already too far away for the living tradition still to offer in itself the least guarantee of authenticity. The oral traditions which Papias echoes arose in the Church and were transmitted by it. For outside the Church no one had any interest in describing in such crude colours the death of the traitor. Papias was therefore deluding himself when he considered viva vox as more valuable than the written books. The oral tradition had a normative value in the period of the apostles, who were eye-witnesses, but it had it no longer in 150 after passing mouth to mouth (Cullmann, 88-89).
What Cullman relates here is that the church (as reported by Papias) had greatly valued the living voice of the Apostles. But they recognized the thing that we (Protestants) have all along been saying: the “living voice” is not a reliable transmitter, after a point. As with the game of “telephone,” where a message becomes badly distorted after being passed from person to person, the value of this “living tradition” had seriously degraded.
The traditions reported by Papias are not the only ones. From the same period we have the first apocryphal Gospels, which were collections of other oral traditions. It is sufficient to read these Gospels, one of which tells of the infant Jesus making living sparrows, carrying water in his apron, and miraculously killing companions who were annoying him, or to read the numerous apocryphal Acts, in order to realize that the tradition, in the Church, no longer offered any guarantee of truth, even when it claimed a chain of succession. For all these traditions were justified by [various chains] of transmission reaching back to the apostles. Papias himself also makes this claim when he says that he got his information from people who had been in contact with the apostles. The teaching office of the Church in itself did not suffice to preserve the purity of the gospel (88-90).This selection is long enough for now. But I wanted to make the essential point: the early church did recognize the weakness of relying on "the living voice."
For more information, see also: Jason Engwer's series on The New Testament Canon.