What I found wonderfully odd in its first appearance in I.1 is that Barth's way of getting to speaking of what Scripture is was in contrast to the Roman Catholic doctrine of apostolic succession. He makes a plea that Protestants be careful to reject the Roman doctrine for the right reasons; apostolic succession cannot be fully rejected as such, but only in its peculiar Roman form in which the manner of succession relates to formal office rather than spiritual service. That is, the spiritual service of the Roman pontiff is seen as included within and guaranteed by the possession of the formal office of the bishop of Rome. As wrong as this is, it is right, argues Barth, that we see the present Church as succeeding the apostles. The Church's proclamation of the Gospel, which is what makes the Church what it is, must rest on a basis external to itself; the Church does not contain its own Gospel, but points past itself to an expectation of a future revelation of God in Christ based on the decisive past revelation of God in Christ. This basis of the Church's proclamation in Jesus Christ is passed from Christ to the world by the apostles so that the Church cannot point to itself as the proper validation of its message but must point to the apostles and therefore seek to succeed them as proclaimers of Christ. However, this succession has to take the proper form. In Roman Catholicism, the current successor of Peter in essence replaces Peter so that in pointing to apostolic testimony for the validation of its proclamation, the Church merely points to itself as the apostolic Church. Barth, however, argues that the current Church in its succession of the apostles cannot seek to replace them but must stand always under them. Scripture is what allows us to succeed the apostles in this way.
Now that I've set it up, here is the paragraph that made me happy and I wanted to share:
The apostolic succession of the Church must mean that it is guided by the Canon, that is, by the prophetic and apostolic word as the necessary rule of every word that is valid in the Church. It must mean that the Church enters into the succession of the prophets and apostles in their office of proclamation, and does so in such a way that their proclamation freely and independently precedes, while that of the Church is related to it, is ventured in obedience on the basis of it, is measured by it, and replaces it only as and to the extent that it conforms to it. It must mean that the Church always admits the free power of their proclamation over it. As far as the idea of a living succession is concerned everything depends on the antecessor being regarded as alive and having free power over against the successor. But if, as here, the antecessor has long since died, this can happen only if his proclamation has been fixed in writing and if it is acknowledged that he still has life and free power over the Church to-day in this written word of his. On the written nature of the Canon, on its character as scriptura sacra, hangs his autonomy and independence, and consequently his free power over against the Church and the living nature of the succession.