In these sections, Barth continues his discussion of the Trinity, and I must say, that after reading his discussion, it is no less a mystery.
Let us deal with his discussion of the vesigium trinitatis first. Are there vestiges of the Trinity in nature, culture, history, etc.? That is, because God created this world, might there not be signs or vestiges, little bits of this world that reflect the trinity of God? It seems reasonable. But, according to Barth, the answer is a resounding NO! Barth is sympathetic with the attempts to use such images as analogies to try and understand the Trinity, but views them as dangerous. And the reason is that there should only be one root of the Trinity and that is revelation attested by scripture. Only God can reveal his triune nature. We cannot first find it in nature and then derive the trinity of God from such. So, vestiges such as "spring, stream, and lake," "water, ice, steam," "Old Testament Age, New Testament Age, Age of the Church" are not really reflections of God's nature, but are attempts to understand the nature of God through more familiar images.
Now, on to Barth's discussion of the Trinity in §9. I will not rehearse his arguments here. They are the common arguments used in the Trinitarian controversies in the 3rd and 4th centuries. Barth is not really positing anything new, but he does suggest the replacement of the term "person" with "mode of being." That is, whereas the previous formulation was that there was "One God in three Persons," should now be "One God in three Modes of Being."
Since the beginning, Christians have attempted to explain two things: 1) they are monotheists, and 2) There is God the Father, God the Son, and God the Holy Spirit.
In trying to explain this, there is always a danger of falling into two primary heretical traps. On one side, the accusation of tritheism is apparent, namely that Christians worship three Gods. On the other side, the accusation of modalism is apparent, namely that Christians are speaking of one God who wears three masks. Barth admits this is a danger. He writes:
"We, too, are unable to avoid the fact that every step of ours in this field is exposed to danger, whether the threat comes from the tritheistic heresy or from the modalist heresy, or whether there be on either side suspicion of the opposite error." (CD I.1 §9.2 p. 368).Thus, in trying to avoid these errors, Barth employs philosophical language meant to steer a middle course, to say God is one essence, but exists in three distinct modes of being, yet at the same time that these modes of being are distinct, the unity is not dissolved, yet the unity does not swallow up the distinction. What?
The problem here is that the doctrine of the Trinity attempts to explain a mystery that cannot be explained. Humans have no analogy to the trinity, in fact, the concept of the Trinity defies basic logic. Three cannot be one and three at the same time. Yet, nonetheless, Christians profess their monotheism while at the same time professing that God exists as Father, Son and Holy Spirit.
I think the reason that I have never been taken with the explanations of the doctrine of the Trinity has to do with my personality type. I am an INTJ. INTJs love deep thought. We love logic games and puzzles, we love philosophical language and distinctions, so long as eventually we end up with a final product that can be directly applied to our real and concrete lives or the lives of those around us. INTJs are thinkers, but not thinking for thinking's sake, but rather thinking for the sake of application. The problem I have with discussions of the Trinity is not that I don't understand all of the philosophical language and the reasons for stating things as carefully as possible, but rather because, at the end of these discussions, I am no closer to actually understanding the Trinity in a way that has application. It is like a mental exercise with no payoff. At the end the mystery is still a mystery, and I am OK with that. As Barth writes:
"On all sides good care is thus taken to see that the mysterium trinitatis remains a mystery." (CD I.1 §9.2 p. 368).I would prefer to say that as God encounters us in the Bible, he does so as Father, Son, and Holy Spirit: One God, three modes of being. Beyond that, I prefer to think about other matters.