I don’t think people realize that Barth (Torrance) isn’t attempting to figure out the riddle of individual belief, as if he can identify a causal system that explains it all. He limits Himself to what is revealed in the Theanthropos, the Godman, Jesus Christ. We know why Jesus believes, trusts the Father; and we know that He does so for us in our stead; and so from thence we know that people believe God because of God’s action in humanity, in the Son. Barth isn’t worried about solving the “causation” enigma, per se; at least not by referring to some speculative metaphysics of causation. But this is why people constantly claim that Barth’s theology must reduce to universalism; even though Barth’s theology only really reduces to the freedom of God to be God as God has always already and eternally been, and continues to be.