Barth's metaphors have to do with seeing, Luther's with hearing. This makes sense in light of how they understand divine revelation. Barth views divine revelation as the unfolding of a single subject (God) in an act of revealing himself in time. He does this by echoing his eternal decision to be "one who loves in freedom" in the temporal narrative of Jesus. This temporal narrative is "unveiling" is further echoed in "Jesus, Bible and proclaimed Word" which echoes the Father, Son and Spirit, as "revealed, revealer, revealing." Barth's view of revelation is essentially analogical. Analogy has to do with a kind of visible similitude between things and therefore envisions human knowledge (following Aristotle) as a kind of intellectual vision.
Luther's theology works on the basis of hearing. In other words, God's agency manifests itself through the law which is present and visible through all creation. Human can observe how the world works and see what God's legal will is. They can also see this in the horrific act of judgment that God causes to take place in salvation history. Nevertheless, God promises his grace and enacts under his act of judgment and under act of weakness. The supreme one is the cross. We are told that Jesus is God and that the cross is an act of grace. Nevertheless, all we see is weakness (a weak, beaten and dying Christ) and condemnation (i.e. a symbol of Israel's sin and continuing exile). Contrary to this, we hear "surely he was the Son of God" and "today you will be with me in paradise." Consequently, revelation's hiddenness is transcended only by hearing the Word. Proper knowledge of God is set against analogical and visible knowledge of God, and placed in the realm of hearing.
Interesting stuff---I'd have to say that these two views are easily reconciled as the human experience with God's revelation of God's self has always been both visual and audible. And as we know God's fullest and final self-revelation was in Jesus Christ Himself---who was both seen and heard as the Word of God Himself. The Trinitarian implications of both of these views can be seen in these ways: Jesus Christ as the Word of God actualized, the Bible as the encounter in which we realize that Jesus Christ is the One True and Living Word of God and the Kerygmatic preaching of Jesus Christ the One True and Actual Word of God in which our Divine Election of and by God is revealed. This Election is most fully realized in the Cross and can only point to Jesus' self-sacrificial death upon the Cross. In this sense also the Word of God, God's revelation of God's self in Christ is both seen and heard as God in Christ is both the subject and object of our faith: the whole content and character of the Christian revelation.
Karl Barth also said in Credo: Volume IV of his Church Dogmatics:
It can be asserted and proved with the utmost definiteness and accuracy that the great theological-ecclesiastical catastrophe of which the German Protestantism of the moment is the arena, would have been impossible if the three words Filium eius unicum ["his only Son"] in the properly understood sense of the Nicene trinitarian doctrine had not for more than two hundred years been really lost to the German Church amongst a chaos of reinterpretations designed to make them innocuous. This catastrophe should be a real, final warning to the evangelical Churches, and, especially to the theological faculties of other lands, where, so far as trinitarian dogma is concerned, no better ways are being trodden. Christian faith stands or falls once and for all with the fact that God and God alone is its object. If one rejects the Bibhcal doctrine that Jesus Christ is God’s Son, and indeed God’s only Son, and that therefore the whole revelation of God and all reconciliaion between God and man is contained in Him—and if one then, in spite of that, speaks of ” faith ” in Jesus Christ, then one believes in an intermediate being, and then consequently one is really pursuing metaphysics and has ready secretly lapsed from the Christian faith into a polytheism which will forthwith mature into further fruits in the setting up of a special God-Father faith and a special Creator faith, and in the assertion of special spiritual revelations. The proclamation of this polytheism can most certainly be a brilliant and a pleasant affair, and can win continuous and widespread approbation. But real consolation and real instruction, the Gospel of God and the Law of God, will find a small and ever-diminishing place in this proclamation. (49-50 – emphasis mine)
And with that I close---so what are your thoughts?