Barth started his CD by discussing about the task of dogmatics and prolegomena to dogmatics. He understood that there is no such thing as a neutral prolegomena. The How (method) of dogmatics is related to the What (content) of dogmatics. Barth then discussed the How of church dogmatics, i.e., the Word of God as the criterion of dogmatics. He discussed the Word of God in its threefold form, its nature, and its knowability. Afterwards, he discussed in details, now not only the form of the Word of God, but also its concrete content. Thus he will proceed with the doctrine of the revelation of God (Word of God revealed), the doctrine of the Holy Scripture (Word of God written), and the doctrine of Church proclamation (Word of God preached).
Who is God in His revelation? Well, we learnt that “God reveals himself. He reveals Himself through Himself. He reveals himself.” (I/1, 296) And thus “this signifies for the concept of revelation that God Himself in unimpaired unity yet also in unimpaired distinction is Revealer, Revelation, and Revealedness.” (295) To put it in other words, the whole doctrine can be summed up as “‘God speaks.’ ‘Deus dixit.'” (296) Thus, we are about to enter the discussion of the doctrine of the Trinity, of which this Revealer, Revelation, and Revealedness have distinct and specific name, that is the Father, the Son, and the Holy Spirit.