Knowledge of God is contingent upon God giving Himself to us and for us. If He simply leaves us awash in a neutered creation, meaning a creation without His Self-givenness, then all the creature has as resource are themselves. This is the status an unbeliever inhabits; a neutered reality that has no possibility for a true knowledge of the true God. There is nothing in the unbeliever’s mind’s-eye that would allow them to transcend the machinations produced by their own belly-buttons. They are simply people, as the ‘teacher’ might say: ‘under the sun.’ So, if this is the case, then why would Christians rely upon non-Christians to ideationally fund their conniving of God in categorical ways? And yet this is what has happened in the main; in the Great Tradition itself. Thomas Aquinas remains the best and most prominent example, particularly because he continues to be the go to saint that even Protestant theologians are resourcing in the current theological moment. Thomas clearly synthesizes Aristotle’s conceptions of immutability, impassibility, pure being so on and so forth into the way he grammarizes God. If this is so, and Aristotle was an unbeliever, and he was, then why should we have confidence that the God Thomas presents, by way of emphasis and categorical conjecture, coheres with the God revealed in Jesus Christ; with the God borne witness to in Holy Scripture?
Barth writes with his usual penetration. Barth challenges the commingling of the Church’s knowledge of God with the world’s. He wonders how there can be a point of contact between a soul that is in definitional enmity with God, and a soul that is union with God in Christ.
It may perhaps be pointed out that the establishment of our knowledge of God in this way is in fact possible and practicable, and that it vouches for its own legitimacy and necessity by its actual fulfillment. But what does it mean to be possible and practicable? And what does it mean that it vouches for itself? We have to do here with the attempt of man to answer the riddle of his own existence and of that of the world, and in that way to master himself and the world; with his attempt to strike a balance between himself and the world; even with his attempt to put these questions in the belief that he can regard the supposed goal of his answers or even the supposed origin of his questions as a first and final thing and therefore as God.
Barth’s doctrine of sin and theological anthropology needs to be acknowledged as we work through these things with him. As a Reformed theologian he operates with a heavy dose of humanity’s total depravity, and the noetic impact that has had upon humanity’s capacity to think God, or to know the real and living God in any meaningful way. Barth, in this sense, has a rather Augustinian conception of what has happened to humanity in the Fall; i.e. the belief that humanity is in bondage to themselves, that they cannot get beyond their own pericardial sac. He takes seriously the Mosaic notion: ‘Then the Lord saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually.’ And the Jeremiahian idea that: ‘“The heart is more deceitful than all else and is desperately sick; Who can understand it?’ Further, Barth might have the Pauline thinking in mind when Paul writes: ‘“There is none righteous, not even one; There is none who understands, There is none who seeks for God;. . .’ And: ‘So this I say, and affirm together with the Lord, that you walk no longer just as the Gentiles also walk, in the futility of their mind, being darkened in their understanding, excluded from the life of God because of the ignorance that is in them, because of the hardness of their heart; and they, having become callous, have given themselves over to sensuality for the practice of every kind of impurity with greediness.’ All of this is in line with what Martin Luther, in contrast to Erasmus, termed ‘the bondage of the will.’ Barth is full-fledged committed to the idea that natural humanity’s capacity to think God from its own resources can only result in a serious case of self-projection and idolatry.
Barth interrogates the legitimacy of the Church’s commingling with the world’s mind further:
It cannot even be discussed because, as we have seen from our debate with the Roman Catholic doctrine, it is possible only on the basis of a mortal attack on the Christian doctrine of God, and it certainly cannot be the case that this attack is the starting-point for the Christian doctrine of God, and with it, dogmatics, and therefore the question of pure doctrine. What good can come of it if at this point we immediately orientate ourselves in another direction than to the basis and essence of the Church? If we allow ourselves this liberty, how will it be with everything else? How are we going to treat the nature of God, and then creation, the Law, the covenant of God with sinful man? Can we ever speak properly of grace and faith if at the very outset we have provided ourselves with a guarantee of our knowledge of God which has nothing to do with grace and faith? Does it not necessarily change and even falsify everything if at this point we are guilty of enmity and conflict against grace?
As we read this we are reminded of the Apostle Paul’s language of being ‘unequally yoked’ with unbelievers:
Do not be bound together with unbelievers; for what partnership have righteousness and lawlessness, or what fellowship has light with darkness? Or what harmony has Christ with Belial, or what has a believer in common with an unbeliever? Or what agreement has the temple of God with idols? For we are the temple of the living God; just as God said, “I will dwell in them and walk among them; And I will be their God, and they shall be My people. “Therefore, come out from their midst and be separate,” says the Lord. “And do not touch what is unclean; And I will welcome you. “And I will be a father to you, And you shall be sons and daughters to Me,” Says the Lord Almighty.
We might even think that throughout Barth’s §26 he has something like the above passage from Paul in mind. Barth’s whole premise is that of Paul’s; i.e. that unbelievers and believers have nothing in common; the idea that believers are the temple of God, whereas unbelievers the temple, so to speak, of Belial or the devil. It is not simply a passive contrast, but an active reality wherein the unbelieving mind is at enmity with God. Barth reasons from these premises that the unbelieving mind, no matter how brilliant, like in the case of Aristotle, has no real contact with the living God. Barth’s contention is that the unbelieving mind is at such warfare status with God, that it has a desire to be its own god, that there can be no reliable connection between the self-desire, and the true God who is defined by an outturned givenness for the other (think of the triune persons in eternal fellowship).
If all of these things be so, then what place is there for a natural knowledge of God? There is none. And if there is none, then no matter how long the activity of synthesizing natural categories of God with revealed ones has been occurring, this activity ought to be repented of. This is challenging because it seems as if God has left Himself without a witness, or so the response might be. But for Protestants this shouldn’t worry us. We are already heirs of a tradition that believes the Gospel was corrupted for centuries by the Church’s teaching. It is unclear to me why Protestants constantly rely on the history of the Church as the bulwark wherein they hope to find stable solace in regard to a knowledge of God. If that bulwark has been built on an admixture of sand and rock there is only a façade of stability to begin with. The Protestant ought to be willing to repent of this foundation, and find solace in the voice of the living God as that is borne witness to afresh and anew in Jesus Christ and in Holy Scripture. This is what I see Barth calling the Reformed churches to: viz. that she would repent of frameworks that portend towards a knowability of God that are built on the foundations delivered not by the Church, simpliciter, but by the wits of unbelieving minds; minds that are naturally and constantly at warfare with the reality of the living and Self-revealed God.
 Barth, CD II/1 §26 (T&T Clark Study Edition), 83-4.
 Genesis 6.5
 Jeremiah 17.9
 Romans 3.11
 Ephesians 4.17-19.
 Barth, CD II/1 §26, 83.
 II Corinthians 6.14-18