Here’s the same problem elsewhere in Barth (again relying on Hunsinger’s treatment):
This encounter with God, he argued, was mediated, not immediate, and was given by grace, not by nature. The encounter was objectively mediated by Jesus Christ, and given only by the free decision of God. The condition for its possibility was thus extrinsic, not intrinsic, to human nature ( How to Read Karl Barth , p. 40).
Here, the problem again is Barth’s doctrine of creation. Despite his hostility to natural revelation, and implicitly to an idea of nature having an autonomy, this is precisely what he ends up with. If humanity or human nature is always already grace and gift, then the whole problem dissolves. Insofar as Barth failed to posit creation as grace, he actually grants considerable autonomy to nature, such that “nature” does not always already possess its reality only in and as encounter with God.
Again, perhaps poorly stated, but I see this nature/grace scheme running along everywhere in Barth, with massive problems resulting. Even while he attacks the scholastics for granting autonomy to nature (some innate capacity for human response residing in human nature) he has granted a far more wide-ranging and fundamental autonomy to nature (because human nature exists but has no innate relationship with God).