1. "I am the way, and the truth, and the life; no one comes to the Father, but by me." (Jn 14.6) "Truly, truly, I say to you, he who does not enter the sheepfold by the door, but climbs in by another way, that man is a thief and a robber... I am the door; if anyone enters by me, he will be saved." (Jn 10.1, 9)
Jesus Christ, as he is attested for us in holy scripture, is the one Word of God which we have to hear and which we have to trust and obey in life and in death.
We reject the false doctrine, as though the church could and would have to acknowledge as a source of its proclamation, apart from and besides this one Word of God, still other events and powers, figures and truths, as God's revelation.
Karl Barth wrote the draft of the Barmen Declaration. He modified it as others, including Martin Niemöller, suggested improvements. In his Church Dogmatics*, Barth discusses the significance of this first article.
First, he thought the Barmen Declaration was important because, through it, the Church—for the first time ever—confronted natural theology and rightly rejected it. Perhaps the Church had waited until 1934 to confront and reject natural theology because only then did Olympian church leaders, who believed in it, threaten so convincingly to make it the “standard and content of Church proclamation and theology” (173).
What was this new form of natural theology that so threatened the Evangelical Church in Germany in 1934? It was the demand that (1) Germany’s new political leader should take his place in the Church alongside Jesus Christ and that (2) his party’s way of thinking should take its place alongside the Bible as the content of the Church’s theology and proclamation. Soon enough, this demand to stand alongside Jesus and Bible in the Church became the command to subordinate Jesus and Bible and then reject them altogether.
Barth noted that this harmful adoption of Olympian worldviews had plagued the Church for centuries. First a few Christians find interesting some form of natural theology and ask the rest simply to allow them to talk about it. As they grow in number and influence, these Christian Olympians demand rather than ask that others also look at Jesus and the Bible through this new worldview. Soon enough Jesus and the Bible are both subordinated to it and then finally rejected. Over the centuries, this “also” which soon enough became an “only,” insisted that, in our modern times, God best revealed himself, not in the Bible, but “in reason, in conscience, in the emotions, in history, in nature, and in culture and its achievements and developments” (173). Christians were supposed to accommodate all of these “also’s” which quickly enough drove them to abandon Jesus Christ as witnessed to by the Bible.
Mercifully, Jesus did not abandon his wayward Church through the centuries. He always maintained the “only” of the Bible in its midst against the counterclaims of others demanding and even coercing the “only” of their natural theology.
Again, the German Christians demanded that a new political leader and the ideology of his party be given priority. This had plenty of historical precedent. From the beginning of the 1700s the Church had granted such a priority to humanism, Idealism, Romanticism, positivism, nationalism, and socialism: “they had all wanted to have their say in the Church. And in face of these clear precedents there could be no basic reason for silencing this new nationalism of race” (174). Indeed, the perception was that this latest form of natural theology “seemed to raise like a tidal wave the ship of the Church which many people felt had run aground, and at last, at long last to  be trying to bear it back again to the high seas of the real life of the nation and therefore into the sphere of reality” (174-5). By affirming the latest natural theology, church members believed they would recover their lost relevance and outsiders would again regard them with respect and join their churches.
Barth thought the rejection by the Confessing Church of natural theology, especially in its latest toxic form, could have far-reaching consequences for good:
For [1a] when in Barmen Jesus Christ as attested to us in Holy Scripture was designated as the one Word of God whom we have to trust and obey in life and in death; [1b] when the doctrine of a source of Church proclamation different from this one Word of God was repudiated as false doctrine; and [1c] when, in the concluding article of the whole Declaration, the acknowledgment of this truth and the repudiation of this error were declared to be the indispensable theological foundation of the German Evangelical Church— an assertion was made which…if taken seriously, contained in itself a purifying of the Church not only concretely from the new point at issue, but from all natural theology (175).With acknowledgment of all natural theologies as falsehoods and disloyalty to Jesus, the next question for the Confessing Church became: how far would they be willing to go in repenting of it? Writing in 1940, Barth observed:
The accumulated errors and vacillations in the Confessional Church are connected with the fact that the insight expressed at Barmen—Jesus Christ is the one Word of God whom we have to trust and obey—did not at first correspond to the flesh and blood reality of the Church but contradicted it, and had still to be repeated, attained and practiced in a wearisome struggle. When this did not happen, no other attitude could be reached in practice than that of partial retreats and compromises. Where it did happen, it carried with it automatically the will and power to resist. The German Confessional Church has either the power of the ecumenical gift and task which  it received and accepted at Barmen, or it has no power. It either fights for the purification of which the Evangelical Church has long been in need and is everywhere in need or in reality it does not fight at all (176).At Barmen, the Confessing Church affirmed that Jesus Christ, as attested by the Bible, is the one Word of God which we have to hear and obey. Barth acknowledged that this affirmation was a miracle: “The fact is that, when nothing else was left for the Church, the one Word of God who is called Jesus Christ remained” (176). He remained alive and well as he does today.
Jesus Christ remained alive and well and savior of his Church solely by grace; that is, without the Confessing Church earning or deserving this unmerited favor at all. “What might have been expected was that…the Church would now be tired and its eyes blurred and it would be inwardly exhausted, so that it would succumb all the more easily and this time for good to the assault of the blatant temptation [of natural theology]. But the fact is that this did not happen. The Word of God still remained, in spite of everything, in the same Church in which it had been so often denied and betrayed” (176).
Jesus Christ remains the only truth who sets us free to love (God especially) and leads us into eternal life (including renewed vitality now). Despite all obstacles, the Tufluvian Christians of the Confessing Church could, with renewed vitality, begin “reading the Bible again, confessing again its clear assertions, and therefore uttering the cry of need and of joy from Barmen. And they could at once stand and hold their position on this ground after all other grounds had crumbled under their feet” (176).
The Confessing Church, Barth emphasizes, was not heroic in battling false gods and their falsehoods. It was “only the witness of a situation in which simultaneously there took place a remarkable revelation, as there had not been for a long time, of the beast out of the abyss [Revelation 11:7], and a fresh confirmation of the one old revelation of God in Jesus Christ. It was obliged to notice what was going to be seen on this occasion—that Satan had fallen from heaven like lightning [Luke 10:18, Revelation 12:9] and that the Lord is mighty over all gods. What it noticed on this occasion was the fact of the unique validity of Jesus Christ as the Word of God spoken to us for life and death” (177).
Having witnessed the miracle of Christ’s sure help in contrast to the certain harm of all worldly leaders and worldviews, Christ then called the Confessing Church to testify to its salvation by Christ through sharing this Good News with the whole Body of Christ. “It will be lost if it forgets this testimony, or no longer understands it, or no longer takes it seriously; the power against which it stands is too great for it to meet it otherwise than with the weapon of this testimony. And it may well be decisive for other Churches in the world, for their existence as the one, ecumenical Church of Jesus Christ, whether they on their side are able to hear and willing to accept the message of the Confessional Church in Germany” (177).
To the Confessing Church in Barmen, Jesus Christ again revealed himself to be our one Lord and Savior as he said he was in the Bible: “I am the door” John 10:7, ESV) and “I am the way, and the truth, and the life. No one comes to the Father except through me” (John 14:6, ESV). “The Church lives by the fact that…it chooses the way, knows the truth, lives the life, goes through the door, which is Jesus Christ alone. Moreover, it is not on its own authority,…but on the basis of the necessity in which Jesus Christ himself has said that no man comes to the Father but by Him, and that any by-passing of Him means theft and robbery [John 10:1], that the Church makes its exclusive claim, negating every other way or truth or life or door apart from Him” (177).
*Church Dogmatics, II.1, “The Doctrine of God”; Chapter V, “The Knowledge of God”; Section 26, “The Knowability of God”; Subsection 2, “The Readiness of Man”; pp 172-8.