From The Theology of Karl Barth by Hans Urs von Balthasar, pp. 218-219:
Critics of Thomas Aquinas have often accused him of being at heart an Aristotelian philosopher who would recast revelation in this mold, thereby constricting it. Nor have critics been slow to accuse Barth of the same thing: taking a fully formed picture of the world — this time, that of German Idealism — and making it the standard for shaping and containing the biblical message.
But this comparison with Thomas Aquinas should give us pause, especially at this most critical juncture of our investigation. Barth himself after all accused Thomas of philosophism, clearly, then, something he wanted to avoid. For at least one fact about Barth is indisputable: Barth has always wanted to be a theologian and nothing else. He has always been aware, increasingly so, of this objection raised against him. He has taken it into account, confronted it: in this respect he is anything but naive.
He knows, and he has repeated it often, that every theologian has no choice but to work with human concepts and thought forms. And if he uses those concepts in which he first learned to think theologically, then he does so in clear awareness of the consequences and because he can find no better. He has made use of them, not as a philosophy per se, but as a helpmate for theological work, transposing them and submitting them to a necessary critique, sterilizing the instruments before using them in his theological operations.
He has made use of them the way Thomas did the Aristotelian categories, which to philosophy would seem illegitimate or at lest “supererogatory.” Fundamentally, we cannot object to such a transposition of categories. Revelation has never revealed that it has been predestined to be expressed in one, single human thought form (this is not to say anything against the content of a “perennial philosophy”). The Old Testament itself thinks and expresses itself in Babylonian and Iranian thought forms. Paul and John use Hellenistic, Platonic and perhaps even Philonic schemata and concepts. Was Platonism not a form of Idealism and is Schleiermacher not a Platonist? And has not Joseph Maréchal proven that certain basic intuitions of modern speculative philosophy are in complete agreement with those of Scholasticism, that the ontological and the transcendental modes do not finally contradict but complement each other?