I read up on Barth’s doctrine of Scripture so you didn’t have to! Here are some of things I found possibly relevant. I have provided comment here and there to put the quotes in context.
Two places in the Church Dogmatics that Barth makes extended comment on the doctrine of Scripture are I/1, §4 and I/2, §19. The bulk of CD I/1 is devoted to the doctrine of revelation, which also provides the context for Barth’s doctrine of the Trinity. That is because the doctrine of the Trinity is an answer to the question “Who is God in his revelation?” (297). Before this, though, Barth provides a preliminary comment on the doctrine of Scripture. He will treat this more extensively in CD I/2, on which I will write a separate post, only after he has detailed the doctrine of the Trinity. Traditionally, Protestant dogmatics addresses the doctrine of Scripture before the doctrine of the Trinity. However,
“The reason why we diverge from this custom is this. It is hard to see how in relation to Holy Scripture we can say what is distinctive for the holiness of this Scripture if first we do not make it clear (naturally from Holy Scripture itself) who the God is whose revelation makes Scripture holy” (300).
“The doctrine of the Trinity itself is threatened by the same danger, the danger of irrelevant speculation, if we state it only at a later stage and do not give it the first word as that which gives us information on the concrete and decisive question: Who is God?” (301).
Barth begins CD I/1 with sections on the task of dogmatics and the prolegomena (§§1-2). He then addresses proclamation of the gospel, the central calling of the church:
“Proclamation is human speech in and by which God Himself speaks like a king through the mouth of his herald, and which is meant to be heard and accepted as speech in and by which God Himself speaks, and therefore heard and accepted in faith as divine decision concerning life and death, as divine judgment and pardon, eternal Law and eternal Gospel both together” (52; cf. 1 Thess 2:13; 2 Cor 2:17; 1 Pet 4:11).
Nonetheless, proclamation is not made proclamation by virtue of human beings proclaiming. God does not even need proclamation, though he chooses to use this. Proclamation is an act of obedience to the commission of God and where he chooses he makes it his own in such a way that speaks to people’s hearts:
“It is always and always will be man’s word. It is also something more than this and quite different. When and where it pleases God, it is God’s own Word. Upon the promise of this divine good-pleasure it is ventured in obedience. On this promise depend the claim and the expectation. But proclamation both as preaching and sacrament does not cease to be representation, human service” (71-2).
Barth includes the sacraments (as a Reformed theologian, baptism and the eucharist) alongside proclamation as the central calling of the church. He does not provide much comment on them here though because the context is revelation. Both proclamation and sacrament are related in that they are at once a fully human work and a work of God. Barth draws on the incarnation here to elucidate this. Just as Jesus is completely human and completely God, none of these being compromised in his being but rather upheld, so too are proclamation and sacrament human works in which God also works.
After addressing proclamation in §3, Barth goes on to address the doctrine of Scripture in §4, “The Word of God in Its Threefold Form.” The event of revelation is God with us, in Christ. This both proclamation and Scripture attest. In his work in proclamation, God directs his hearers back to himself in the person of Christ, by which he made himself known to human beings (revelation here also has a future element in which God will be fully revealed with the coming of the kingdom. Barth’s focus here though is on this retrospective aspect).
The middle term of revelation, Scripture, differs from proclamation:
“The distinction of the Head from the body and the superiority of the Head over the body find concrete expression in the fact that proclamation in the Church is confronted by a factor which is very like it as a phenomenon, which is temporal as it is, and yet which is different from it and in order superior to it. This factor is Holy Scripture” (101).
“With its acknowledgment of the presence of the Canon the Church expresses the fact that it is not left to itself in its proclamation, that the commission on the ground of which it proclaims, the object which it proclaims, the judgment under which its proclamation stands and the event of real proclamation must all come from elsewhere, from without, and very concretely from without, in all the externality of the concrete Canon as a categorical imperative which is also historical, which speaks in time” (101).
That is, if Scripture is just another form of proclamation then there is nothing by which the church can measure the validity of its proclamation. Not only would the proclamation of the church be disputable but Scripture itself. God would not have spoken. Moreover, Barth contends that the nature of Scripture as writing is essential to its role in relation to proclamation. An oral tradition, for example, lacks this same concreteness and can too easily be manipulated by successive generations. But the written word maintains a relative consistency from which it can confront the limits of proclamation. Anticipating the critique I had in mind here, that a written Scripture is as much open to abuse as an oral one, Barth writes,
“Nor will one banish the danger, but only conjure it up properly and make it acute, by making correct exposition dependent on the judgment of a definitive and decisive teaching office in the Church or on the judgment of a historico-critical scholarship which comports itself with equal infallibility. If we assume that one or other of these authorities is worthy of the Church’s highest confidence, then either way the Church goes astray in respect of the Bible by thinking that in one way or the other it can and should control correct exposition, and thereby set up a norm over the norm, and thereby capture the true norm for itself. The exegesis of the Bible should rather be left open on all sides, not for the sake of free thought, as Liberalism would demand, but for the sake of a free Bible. Here as everywhere the defence against possible violence to the text must be left to the text itself, which in fact has always succeeded in doing something a purely spiritual and oral tradition cannot do, namely, maintaining its own life against the encroachments of individual or total periods and tendencies in the Church, victoriously asserting this life in ever new developments, and thus creating recognition for itself as a norm” (106).
This is a necessary inference. If God works in proclamation such that he really does reveal himself in the midst of human words, then it is true here also with Scripture. Amid the vicissitudes of human interpretation, the written word maintains a kind of constancy against its interpretations which God brings to light again and again to call the church back to its roots in revelation.
Like proclamation, nonetheless, Scripture is human words through which God speaks. It is a witness to revelation, which is Christ. Of John the Baptist’s witness to Christ, then, Barth writes,
“Why and in what respect does the biblical witness have authority? Because and in the fact that he claims no authority for himself, that his witness amounts to letting that other [revelation] itself be its own authority. We thus do the Bible poor and unwelcome honour if we equate it directly with this other, with revelation itself” (112).
Yet this does not mean a denigration of Scripture. Rather, Barth seems to be reluctant to go anywhere which would effectively equate Scripture with God. He maintains, however, that it really is God’s Word:
“To hear the Bible as God’s Word means, therefore, that then and there, in the undoubtedly very modest, changing, perhaps increasing but possibly also decreasing compass in which it is true at any given time for an individual, we hear the human words of the Bible as the bearers of this eternal Word, based on this centre and having it in view again in everything they say. When the Bible itself is revelation in this way, it establishes the Church and makes its proclamation necessary and possible. The unity of revelation guarantees the unity of the biblical witness in and in spite of all its multiplicity and even contradictoriness” (116-117).
At the end of the section Barth asserts the unity of revelation in its threefold form.
It is useless to attempt to “understand the three forms of God’s Word in isolation. The first, revelation, is the form that underlies the other two. But it is the very one that never meets us anywhere in abstract form. We know it only indirectly, from Scripture and proclamation. The direct Word of God meets us only in this twofold mediacy. But Scripture too, to become God’s Word for us, must be proclaimed in the Church” (121).