This is a subsidiary post of Apostolicity and the New Testament.
The ancient church established a canon of new scripture (what came to be called the “New Testament”) that it added to what we call the Old Testament, together forming what Christians today call “the Bible.” Modern scholars tell us that the writings that qualified for inclusion in this new scripture were chosen by the ancient church based on various criteria. The essential criterion among these was apostolicity. That is, the writing must be traced to an apostle – an apostle being someone chosen by Christ to be a witness of His resurrection.
Not only is the criterion of apostolicity the sine qua non for inclusion in the New Testament canon, R. Laird Harris points out that it becomes even more critical the farther back in time we go. This makes sense because people tended to lose some focus on the criteria for canonicity once the canon was closed. That can certainly be seen today when people have to be taught or reminded of the criteria. The critical point for us to see is that no text could have made its way into the canon unless it was deemed apostolic.
Therefore, canonicity is a proxy for apostolicity. That is, if we want to know which ancient writings that the ancient church thought came from the apostles, all we have to do is look at their canon. Modern scholars may not agree with the choices that the ancient church made, but the die is cast. By that I mean that it is too late for antiquity to change its mind. The authorship of every document in the canon was deemed to be apostolic; otherwise, the ancients would never have included it. A modern scholar may disagree with the verdict of the ancient church and come up with a different one of his own, but he cannot induce the ancient church to change its mind. It’s too late for that.
There are no writings in the New Testament that antiquity did not deem to be apostolic. Neither were there any documents deemed to be apostolic that antiquity excluded from the canon. Therefore, if a writing is canonical, it was considered apostolic; if it was considered apostolic, it was made canonical.
So, to summarize, and to put the issue in blunt terms, we don’t need to care about the canon. “Canon” is an ecclesiastial term. It’s a way of saying “the church’s official books” which makes “canon” a church pronouncement. This would be like calling the books of the Old Testament “the official books of the ancient nation of Israel.” Such an announcement would be irrelevant to the crucial issue, which is that the Old Testament is the collection of writings from the prophets of God. Similarly, the New Testament is the collection of the writings of the apostles of Christ, who are ipso facto the spokesmen of God just as the prophets were. In other words, we are interested in a historical answer to the question of which writings are those of the apostles – not an ecclesiastical one. Therefore, when we hear that the ancient church “canonized” these 27 books, we rightly understand that to mean that they considered this collection as being all those documents which we have from the apostles. It’s the apostles who have authority – not churchmen.
The writings of the apostles would have been considered apostolic from the moment they wrote them. However, the view that they were canonical would take time. Since only what was considered as apostolic was ever ultimately considered canonical by the ancient church, we are right to view the two terms as synonymous for all practical purposes.