Barth has previously stated that the Word of God comes ubi et quando visum est Deo (where and when it pleases God). He has torn down the notion that the Word of God can be contained in the Bible or in human preaching. No human means, medium, or capacity can contain, hold, possess the Word of God. Now, Barth comes to the most personal, and perhaps the most universal of all human phenomena: experience.
Can we experience the Word of God. Absolutely, Barth is unequivocal on this matter. The knowability and possibility of experience of God's word is a presupposition of the church. If we cannot know or experience God's Word, then what use is there of even speaking of God's Word, or of believing God's Word at all. So, yes, we can experience God's word. Yet, we cannot possess it, even in our experience.
To make things clear, Barth refers to what he calls indirect Christian Cartesianism. This is of course based on the french philosopher Renee Descartes. Descartes wanted to find absolute certainty in life. So, he began by doubting everything that he could possibly doubt. In the end he doubted nearly everything, including his sense perceptions, for they could be the trick of some deceitful demon. Yet, the one thing he could not doubt was that he was thinking about doubting everything. The very fact that he was thinking was certainty in his own mind that he, in fact, existed. Hence, "I think therefore I am."
Barth has previously denounced direct Christian Cartesianism, railing against Schleiermacher and his heirs in their insistence on a capacity in humanity for divine relationship, that is, something in humans which allow them to commune with God. Now, Barth will dismiss "indirect" Cartesianism, which means that God imparts to humans this capacity, but then, once imparted, that capacity for human-divine communion passes from God to the man or woman as his or her possession. Barth will have none of this. For Barth, while the Word of God does carry with it this possibility of human acknowledgment, and does impart this to certain men and women at certain times, this capacity never passes to humans as a possession. No, it comes and it goes.
Therefore, there is no such thing as human certainty about the Word of God. There is no exercise similar to Descartes' in which the human can gain absolute certainty with relation to the Word of God. If that were the case, the Word of God would then be at the disposal of men and women and would no longer remain free. God's Word comes at his will in an event and an encounter with specific men and women at specific times, but the Word does not pass to humans. It retreats again at God's will and remains free.
Here is the money quote for me.
"If a man, the Church, Church proclamation and dogmatics think they can handle the Word and faith like capital at their disposal, they simply prove thereby that they have neither the Word nor Faith." (CD I.1 §6.3 p. 225).Barth's theology in this doctrine of the Word of God is a remarkable defense against the common propensity of humans to have certainty in their wielding of the "Word of God" or of the "Truth." Too often Christians have left their humility behind and stated this or that is the "Truth." We have a name for these people, and it is Bible beater. You know the ones, "God says this," "God says that," "The Bible condemns this," etc. Yet, what they usually mean is "I think God says this or that," or, "according to my interpretation the Bible says this." What it also often means is "I don't like what you are doing, and therefore, God condemns you." For Barth, no one possess the Word of God. The Bible does not even possess the Word of God. The Word of God speaks as he wills. Thus, perhaps, with Barth, we should all just say, we are seeking the Word of God, awaiting it in faith, standing on the promise, but we have no absolute certainty, only faith.