Barth, CD I/2, p.842:

... [we] exclude the possibility of a romantic dogmatics, a dogmatics which does not start honestly from the Church of the present day, but goes back more or less successfully to the past and critically or uncritically tries to think and speak from the standpoint of a past century of the Church. Now it is implied in what we have defined as its confessional attitude that dogmatics has to think and speak in constant contact with the history of the Church, in the unity of the Church of all time. But this does not mean that it must pretend to be a primitive Christian dogmatics or one belonging to the 4th or 16th or 17th century, though if it did, in many respects it would no doubt be more imposing, profound and pious, more rich in content, than if tried to be simply a modern dogmatics speaking in and to the Church of the present. If we think we can meet the needs of the contemporary generation by retiring to the secure ground of a better epoch of the past, and engaging in a process of excavating and rehabilitating, we may obtain the specious results which can always be obtained when ghosts are conjured. But we must add that the Church is not edified by magic of this kind, and that therefore dogmatics must divest itself of romantic as of every other form of magic. The ghosts even of the true Church of the past may lead the Church astray and into temptation no less than the spirits of the present.

How perfectly put!

Barth, CD I/2, pp.829-832:

In this sense, and corresponding to our own direction into the Church, we have marked off the Evangelical Church as the Church of Jesus Christ from the three heresies: Neo-Protestantism, which at almost every point resembles the Evangelical Church in organization and administration but is essentially alien to it in spirit; Roman Catholicism; and the Eastern Orthodox Churches. But even when Neo-Protestantism is strictly excluded as foreign to it, as in this discussion, it is obvious that the Evangelical Church is not a unity. At least three great forms are to be distinguished in it. And to some extent they have distinguished themselves with the same definiteness as if it were a question of an opposition between the Church and one of the heretical sects. These are the Lutheran, the Reformed and the Anglican branches of the Evangelical Church. Let us admit at once that when we speak of the Evangelical Church and therefore of the Church generally in this presentation of dogmatics we mean the Evangelical Reformed Church, in conformity with our own Church position, and the fathers and the dogma to which we owe loyalty in obedience to the Word of God until we are led by that same Word to something better...

Even within the Evangelical Church we have only the one choice, which is no choice. A false choice jeopardizes the whole character of dogmatics as Church dogmatics. We must take upon ourselves a necessary opposition to other types of Evangelical dogmatics. We cannot practice indifferently Anglican, Lutheran or Reformed dogmatics, but only Reformed dogmatics. By this we mean the dogmatics of the particular Church which was purified and reconstituted by the work of Calvin and the confession which sealed his testimony.

As Reformed thinkers, it is impossible for us to say of the Anglican and Lutheran Church, as we do of the Roman Catholic Church, that in them also there is a Church; we must say of them what in view of their doctrine may seem strange and difficult to approve, that in another form they are the one Church of Jesus Christ just as much as is the Reformed Church. The grounds of objection and division are not heresies but specific errors, specific theological notions, badly, misleadingly, erroneously and arbitrarily construed, of a type which may easily arise within the Reformed Confession itself without necessitating disruption...

What we feel is that, though their doctrine is imperiled by what we consider their errors, it does not exclude them from the one Church which is ours.

Well, then.  All clear now?

Barth, CD I/2, p. 808:

...there exists in the Church, before heresy arises... the possibility that a false moralistic earnestness will dominate proclamation, as though it is man's affair whether it is victorious or defeated, as though man has to make the Word of God powerful by the weight of his own will, as though it lies in man's hands to compel decisions about it. When this is the case, the Church strengthens itself to serve the Word of God, as though it is a matter of the organization and running of a business, or the instituting and carrying through of a great law-suit, or the deployment and operations of an army... it is impossible to handle the truth this way.  As a rule, this kind of ecclesiastical earnestness involves a trimmed and therefore a truncated version of the truth. It may not be guilty of actual heresy, but it presupposes a deviation which sooner or later will lead to heresy.

Barth, CD I/2. p. 808:

The truth which the Church has to preach will not be the truth of God if it does not have also its own characteristic beauty. But this very beauty can seduce the Church into treating it as we do other beautiful things, i.e., a dilettante contemplation and enjoyment. But it is beautiful only in order that its work may be done all the more joyfully. If instead of calling to decision it becomes an object of contemplation, it ceases to be the truth.

Complex argument, hard to represent in a brief extract. Barth, CD I/2, p. 803:

Let us suppose the ideal case. We have a form of teaching which in its origin and first appearance, in spite of and in all its human conditioning, can only be traced back to the faithful and true hearing of the Word of God, so that what it says may be defined as the realization of pure doctrine and as the unadulterated proclamation of the Word of God. Why should we not say so at once, even if we can do so legitimately only in faith? But then the teaching goes beyond the stage of origin and first appearance. It passes from the first mouth to the second. Or it is even stated a second or third time by its first exponent. And even in the ideal case, it inevitably becomes dubious. For there is uncertainty whether this still happens in the originally faithful and true hearing of the Word of God. Perhaps the teacher concerned and the teaching church which follows him and uses his formula are already listening to themselves; to the fine and strong and timely things which they themselves have thought about the matter; to the joyful and pleasant sound which the words in question had in their mouths; to the echo of the approval and applause which they encountered; to the consequences of being publicly committed through speaking in this way to the persuasive power of a rapt congregation which wants to hear again and again what has been so wonderfully stated. Even affirmations, denials, syntheses and reservations which, as made in the original hearing of the Word, were well founded and legitimately impressive and - we will suppose - the purest doctrine, now take on a certain independence, or appear only as facile arguments, useful stones in structures with which, as originating in the Word of God, they had nothing to do, and which perhaps themselves derive from quite another source than the hearing of the Word of God. In short, the equivocal phenomenon of Church proclamation has again developed from what we will suppose was the unequivocally pure doctrine of the beginning. This development cannot be arrested. This is how it has always gone at the crises of Church history. As such, the teaching of the Church is not guaranteed even for a single moment against the possibility of immediately losing what we will suppose is its recently attained purity, and of again becoming something very different from the speech which obediently listens. A formula may be ever so simple, clear and powerful, an exposition and sequence of thoughts may be ever so transparent and compelling, but it is not guaranteed against this risk. It cannot be protected by any personality, however trustworthy, or any fellowship of believers, however faithful. Here at the very centre of its life the Church experiences the fact that it is in the world. Its proclamation begins, as we will suppose, in the Spirit, but immediately and at every point it shows a tendency to end in the flesh.

Later, on p. 807:

At every moment and in every situation the danger threatens that members of the Church may want the Word of God without God, bringing it under their power and understanding, and applying it according to their own good pleasure... No heresy has ever had the original intention of being heresy; it has become so only when and where a first unintended lapse from obedience has not been noted and resisted in time.

Barth, CD I/2, p. 750-751:

The human impossibility of the Church's proclamation consists simply in the impossibility of the attempt to speak of God....

Of God it is impossible to speak... If we speak of Him, we are no longer speaking of Him. In this matter we cannot do what we want to do and we cannot attain what we should like to attain. This is the iron law under which all Church proclamation without exception stands. That what happens here is frailty is far too weak an expression for the real situation. This is not frailty. This is death. This is not difficulty. It is sheer impossibility. What happens here is not something imperfect. Measured by the standard of what is intended, it is simply nothing.

If there is proclamation, if the attempt does not fail, it is just at the point where success is achieved that it can and will be understood, not as human success, but as a divine victory concealed in human failure, sovereignly availing itself of human failure.

Barth, CD I/2, p. 748-749:

If we consider what men are doing in the Church, ourselves or others, it is only by a crude self-deception that we can come to the conclusion that the Word of God is really being preached there. And when we have grown tired of this self-deception, if we still consider men in the Church, we shall arrive at the diametrically opposite but no less arbitrary conclusion, that the Word of God is not being preached in the Church...

What has to happen in order that the proclamation of the church may be the Word of God, and that men in the Church may really proclaim the Word of God, has already happened, as, generally speaking, everything that has to happen in order that the Church may live as the Church of God has already happened. Provision has been made that in the Church men may again and again believe and hope and love, that in it the name of God may be constantly invoked in thankful prayer, that in it the disciples of Jesus may ever and again suffer, and that in it brother may find brother and receive his help.

All that has been provided. No presupposition is required from us. We are not even asked whether we see it all performed and fulfilled by ourselves or others. Our business can only be that of accepting as something which has happened for us and to us that which has already been performed and fulfilled in Jesus Christ in respect of the whole life of the Church. It is always in this acceptance that the Church lives its life as created by Jesus Christ and rooted in him.

The same is true in relation to the proclamation of the Word of God, which is only one of the functions of the Church. It can only be a question of accepting what has already been created and founded in Jesus Christ. It is not we who have to care for the truth and validity of the identification of proclamation in the Church with the Word of God. We have to accept that it is so and allow it to be true.

Because Jesus Christ is risen, because God's revelation and testimonies are therefore given to the Church, it receives and holds His commission, which means that it has Himself in its midst as the Lord of its speaking, the Lord who in and through its speaking bears witness to Himself. Humanly speaking, it is a stark impossibility which stares us in the face - that men should speak what God speaks; but it is one which in Jesus Christ is already overcome. At the hands of those for whom it was in fact an impossibility, it brought as a blasphemer to the cross the One for whom it was not an impossibility, in order that it might be revealed in His resurrection as the new possibility for man, to be imparted by Him to His prophets and apostles and to be conveyed by their witness to the Church.