In AD 325 the Council of Nicaea affirmed the divinity of Jesus in the creed of Nicaea. This led to the emergence, over fifty years later, of the Nicene Creed, which defines the faith of the Christian church world-wide. At the heart of both stands the affirmation that Jesus Christ is 'God from God, light from light, true God from true God, begotten, not made, of one being [homoousios] with the Father, through whom all things were made . . .' The intention of both is clear. They wish to affirm with unambiguous clarity that Jesus is to be identified as God incarnate - God has not merely come in a human being but as human. What is less obvious is that the issue at stake here concerns the very possibility of Christian God-talk. Without this decisive affirmation, it is questionable not only whether the Christian church would have continued to exist, but whether its existence would have been warranted. The whole raison d'être of the church is the recognition that Jesus is not simply a good person, or an inspired prophet, or a person with spiritual insight but, rather, the very presence of God identifying with humanity and revealing himself to humanity in a reconciling act of pure and unanticipatable grace.

Karl Barth's approach to the doctrine of God is manifest materially in his discussion of the doctrine of the Trinity, as also in the way in which he relates this doctrine to those of revelation, election, creation and reconciliation. To get to the heart of Barth's understanding of God, however, one is required to recognize its formal significance and, more specifically, the fact that his theology takes place within a church dogmatics. In contrast to so many major theological expositions in the history of thought, Barth refuses to treat the doctrine as if it had a self-contained locus within a 'systematic theology' or exposition of Christian doctrine. How Barth treats the doctrine of God and how he conceives the whole task of dogmatics are irreducibly interrelated. It is this interrelationship which constitutes perhaps the most distinctive facet of his whole approach and with which one must begin.