From a paper I recently wrote on Luther’s “Theology of the Cross”:
“No theologian receives a longer entry in the index volume to Karl Barth’s Chruch Dogmatics than Martin Luther… It suggests that Luther was a towering figure in Barth’s mind.” In this article, George Hunsinger details several aspects of Barth’s theology that are heavily influenced by Luther. “Theology of the Cross” is one of the specific areas of influence, but the other areas are directly related to it as well: Christocentric theology, primacy of the word of God, simul iustus et peccator, and grace and freedom. In fact, Barth’s most distinctive theological notes can be seen as a transposition of Luther’s theology of the cross: “The christocentrism for which Barth is so famous would hardly have been thinkable without Luther’s reformation breakthrough.” He follows Luther in using paradox to explicate this: “This One is the true God… the One whose eternity does not prevent but rather permits and commands Him to be in time and Himself to be temporal, whose omnipotence is so great that He can be weak and indeed impotent, as a man is weak and impotent.” Yet, Barth refuses to follow Luther into his “hidden God” dilemma:
What is not so obvious, however is how far Luther really thought he could overcome this difficulty by his advice that we should worry as little as possible about the Deus absconditus and cling wholly to what he called God’s opus proprium, to the Deus revelatus, and therefore to the God revealed in Jesus Christ. For how can we do this genuinely and seriously if all the time…there is not denied but asserted a very different existence of God as the Deus absconditus, a very real potential inordinate in the background?
The cross is “the deepest revelation of God’s being, not its contradiction.” Barth is able to avoid this because he relativizes all of theology, including the cross, to the person of Christ himself: “The articulus stantis et cadentis ecclesiae is not the doctrine of justification as such, but its basis and culmination: the confession of Jesus Christ, in whom are hid all the treasures of wisdom and knowledge.”Christ is the starting point of all doctrine, not merely one aspect of his work, whether justification or his accomplishment on the cross. By shifting theology from a cruci-centric to a Christo-centric theology, he is able to include the absolutely necessary piece which is “Theology of the Cross” within a framework in which it can do its best work. “In a way that was foreign to Luther, he integrated the hidden God and the revealed God, making them two different aspects of the one God taken as a whole… yet such powerful themes as substantive christocentrism, the theology of the cross, the primacy of God’s work… are no small legacy for one great theologian to have bequeathed to another.” In seeking to appropriate the Theology of the Cross, Barth, and not the Lutherans seems to be our best example.
 George Hunsinger, “What Karl Barth Learned from Martin Luther.” Lutheran Quarterly XIII (1999), 125
 Ibid, 132
 Karl Barth, Church Dogmatics, IV/1, The Doctrine of Reconciliation (ed. G.W. Bromiley and T.F. Torrance, trans. G.W. Bromiley; Peabody, MA: Hendrickson Publishers, 2010), 129
 Barth, Church Dogmatics, vol. II/1, The Doctrine of God , 542
 Hunsinger, “Barth,” 135
 Barth, Church Dogmatics, IV/1, 527
 Hunsinger, “Barth,” 147