In his commentary The Epistle to the Romans Barth argued that the God who is revealed in the cross of Jesus challenges and overthrows any attempt to ally God with human cultures, achievements, or possessions. Many theologians believe this work to be the most important theological treatise since Friedrich Schleiermacher's . In the decade following the First World War, Barth was linked with a number of other theologians, actually very diverse in outlook, who had reacted against their teachers' liberalism, in a movement known as dialectical theology. Other members of the movement included Rudolf Bultmann, Eduard Thurneysen, Emil Brunner, and Friedrich Gogarten.
The nativity mystery “conceived from the Holy Spirit and born from the Virgin Mary”, means, that God became human, truly human out of his own grace. The miracle of the existence of Jesus, his “climbing down of God” is: Holy Spirit and Virgin Mary! Here is a human being, the Virgin Mary, and as he comes from God, Jesus comes also from this human being. Born of the Virgin Mary means a human origin for God. Jesus Christ is not only truly God, he is human like every one of us. He is human without limitation. He is not only similar to us, he is like us.
This means to Barth, God's presence in our world, His presence as man among men and therefore God's revelation to humanity. It also means humanity's reconciliation with God. To Barth, this happened and still happens, it is the substance of the Christmas message. This God is conceived where we all are conceived. He is born of Mary. She who conceived and bore Him, plays our part in the wonder of Christmas, for it concerns us. God has come to us. "Disguised in our flesh and blood, is the Eternal God."
The Nicene Creed says: Et incarnatus est de Spiritu Sancto ex Maria virgine et homo factus est. In Barth's theology – in contrast to much of the contemporary liberal theology – this statement is interpreted to mean the dogma of the Virgin Birth. It means that Jesus as a human does not have a father, in the same way that as the Son of God he has no mother. The Holy Spirit, through whom Mary conceived, is not just any spirit, it is God himself whose act must be understood spiritually and not physically. Mary is "full of grace" according to Barth, but this grace is not earned but totally given to her. This is quite similar to Catholic teaching, in which Mary, "by sheer grace," received the fullness of grace from God at the moment of her conception, that she might give her consent at the annunciation. Barth argues that the Church adopted its doctrine of the perpetual virginity of Mary not because of Mary, but in defence of its Christology.
Mother of God
Karl Barth states that as a Christian and theologian, he does not reject the description of Mary as the "Mother of God." To him, this is a legitimate expression of Christological truth. The description of Mary as the "Mother of God" was and is sensible, permissible and necessary as an auxiliary Christological proposition.
Critique of the Catholic view
Barth on the other hand sees the term "Mother of God," as "being overloaded by the so-called Mariology of the Roman Catholic Church". He considered the Roman Catholic veneration of Mary a terrible mistake and heresy.
Where ever Mary is venerated, and devotion to her takes place, there the Church of Christ does not exist.
Mariology is an excrescence, i.e., a diseased construct of theological thought. Excrescences must be excised.
He warns however, of extending this critique too far: And, Barth equally attacks Protestant theology on this issue: "For justice sake, one has to say, that the Protestant rejection of Roman Catholic mariology and Marian cult is dishonest, as long as Protestantism is caught in the same unreal problem". He was a close friend of Hans Urs von Balthasar, who published about him. Barth’s dogmatic theology was partly based on Thomas Aquinas, although he departed from Aquinas on many characteristically Catholic points.
