Barth, in one sweeping sentence, shows us why the self-consciously postmodern theology of our era will not pass the test of time. Although perhaps this kind of theology does not wish to pass such a "modern" test!
In theology, at least, we must be more far-sighted than to attempt a deliberate co-ordination with temporarily predominant philosophical trends in which we may be caught up, or to allow them to dictate or correct our conceptions.
Of course it should be remembered that Barth wrote this on the brink of his engagement with the existential philosophy of Sartre and Heidegger. Perhaps all those works that show us how Richard Rorty illuminates the thought of Pseudo-Dionysius the Areopagite have a place, after all.