The sheer reality of Jesus Christ is, Barth argues ( Church Dogmatics The Doctrine of the Word of God, Volume 1, Part 2: The Revelation of God; Holy Scripture: The Proclamation of the Church , 31 ), the demonstration that God is “God not only in Himself but also in and among us, in our cosmos, as one of the realities that meet us.” This does not involve any curtailment of God’s power, but is itself a demonstration of His power:

“The reality of Jesus Christ, consisting in the fact that God is this Man and this Man is God, invariably asserts that God can cross the boundary between Himself and us; or expressed in general terms, between His own existence and the existence of that which is not identical with Himself. However strictly this boundary line may be drawn and remain drawn - and we do not find it easy to think strictly enough about it - it is no obstacle to him in the act of His revelation. His nature as God compared with our nature as men, His nature as Lord, Creator, Reconciler and Redeemer compared with ours as creatures and sinners doomed to die, does not limit Him in such a way that, in spite of all, He cannot be God within the sphere indicated by this nature of ours. His majesty so great that even in the lowliness of his God-existence of His in our sphere, even when identical with one of the realities of our cosmos which meet us, and precisely in the midst of this lowliness, it can still be majesty, indeed in that very way it can show itself to be majesty.”

He supports this by citing a remarkable passage from Nyssa’s Great Catechism (24):

“For that something pre-eminently great should be wrought out by Divine power is, in a manner, in accordance with, and consequent upon the Divine nature; nor is it startling to hear it said that the whole of the created world, and all that is understood to be beyond the range of visible things, subsists by the power of God, His will giving it existence according to His good pleasure. But this His descent to the humility of man is a kind of superabundant exercise of power, which thus finds no check even in directions which contravene nature. It is the peculiar property of the essence of fire to tend upwards; no one therefore, deems it wonderful in the case of flame to see that natural operation. But should the flame be seen to stream downwards, like heavy bodies, such a fact would be regarded as a miracle; namely, how fire still remains fire, and yet, by this change of direction in its motion, passes out of its nature by being borne downward. In like manner, it is not the vastness of the heavens, and the bright shining of its constellations, and the order of the universe and the unbroken administration over all existence that so manifestly displays the transcendent power of the Deity, as this condescension to the weakness of our nature; the way, in fact, in which sublimity, existing in lowliness, is actually seen in lowliness, and yet descends not from its height, and in which Deity, entwined as it is with the nature of man, becomes this, and yet still is that.”

Barth offers a daring gloss: Unlike flame that is “bound to its own nature” as “the very sign of its creatureliness,” God’s greatness is “not tied down and limited by His own nature.” By this Barth means that God’s transcendent power, which is high, can “bow down to that which is lowly and itself appears in lowliness” yet “without descending from its height.”