Knowledge of God is the key, that is to the ‘secret of creation.’ If “Jesus Christ is indeed the real ground of creation,”[1] then in order to know what in fact creation is for, we must first know its Creator. But as Karl Barth underscores, in a rather Athanasian key, if Jesus is the ground of creation, and if Jesus is indeed the ‘Son of the Father,’ then to know the 
inner-ground, the secret of creation is first to know Jesus, to know the Son. As such, prior to knowing what and who creation is for, as the case may be, we must first come to know the Creator not as brute Creator, but as Father of the Son. It is from this frame of reference the Christian principially will come to think God all the way down; down into the flesh and blood humanity of the Son become man in Jesus Christ. This implicates, it even contradicts the classical theistic and/or scholastic mode for attempting to know God. This ‘mode’ thinks God by a prior means, by speculating upon the creation, with the philosophers, before coming to know God as Son of the Father; and thus, as Father of the Son. Because they fail to think God from God’s Self-revelation in Jesus Christ, all the way down, they end up thinking from an abstract place about both the who-ness and what-ness of the living God. Once they establish that God exists (like Thomas in his Prima pars), they then are ready to think God as Son of the Father. But you see what this step does: It inherently ruptures the creation from the Creator, such that the former, at an epistemological level, comes to predicate the latter at an ontic level. Barth rightly excoriates such epistemologies as failures at more accurately knowing the living God; he rejects this type of natural theologizing at the very get-go, as would his patron saint, Athanasius.
What many of the Reformed of today might find troubling is that Barth can appeal to the namesake of the Calvinists himself, John Calvin. Barth can find commentary from Calvin on cognitio Dei (‘knowledge of God’) that militates against the natural theology of the scholastics Reformed. Even if Calvin has some dissonance, ultimately, that is when it comes to presenting a coherent position on knowledge of God, vis-à-vis his duplex cognitio Dei (‘twofold knowledge of God’), it is precisely in this dissonance that ripe fruit can be plucked by Barth in service of making his case for the inner reality of creation being God’s covenant life of grace for the world in Jesus Christ; and thus, to know creation as creation is to first know it as that is gift in God’s life of grace for the world come down in the Son of Man, Jesus Christ. Here Barth plucks Calvin’s fruitfulness found in what better place, but Calvin’s commentary on Genesis. Note how he puts Calvin to his services:
To my knowledge, the strongest testimony of theological tradition in this direction is Calvin’s foreword to his Commentary on the Book of Genesis (1554). In this work he recalls 1 Cor. 1:21: “For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.” What Paul obviously means is: it is in vain for God to be sought by reference to visible things, and indeed that anything should remain, except so that we should be brought straight to 
Christ. Therefore we should make our beginning not with the things of this world, but with the gospel, which puts forth one Christ with his cross and holds us in him. In view of this, Calvin’s conviction is also: indeed it is vain for any to philosophize in the manner of the world, unless they have first been humbled by the preaching of the gospel, and have instructed the whole compass of their intellect to submit to the foolishness of the cross. I say that we will find out nothing above or below that will lift us to God, until Christ has educated us in his school. Nothing further can be done, if we are not raised up from the lowest depths and carried aboard his cross above all the heavens, so that there by faith we might comprehend what no eye has ever seen, nor ear ever heard, and which far surpasses our hearts and minds. For the earth is not before us there, nor its fruits supplied for daily food, but Christ himself offers himself to us unto eternal life; nor do the heavens illuminate our bodily eyes with the splendor of the sun and stars, but the same Christ, the light of the world and the sun of righteousness, shines forth in our souls; nor does the empty air spread its ebb and flow around us, but the very Spirit of God quickens and enlivens us. And so there the invisible kingdom of Christ fills all things, and his spiritual grace is diffused through all things. To be sure, this ought to prevent us from looking to heaven and earth as well and in this way fortifying ourselves in the true knowledge of God. For Christ is the image, in which God not only allows his breast to be seen, but also His hands and feet. By ‘breast’ I mean that secret love, by which we are enfolded in Christ; by ‘hands’ and ‘feet’ I understand those works which are set before our eyes. But: As soon as we have departed from Christ, there is nothing is so gross or trivial that we can avoid being mistaken as to its true nature. (C.R. 23, 10 f.). We do not find in Calvin any more detailed explanation or exposition of this programmatical assertion either in the Commentary on Genesis or in the relevant passages in the Institutio. Yet there can be no doubt that he has given us a stimulus to further thinking in this direction. The step which we ourselves have attempted along the lines he so impressively indicated is only a logical conclusion which is as it were set on our lips by the statements of the fathers, although they did not draw it for themselves.[2]
As Barth notes, whilst Calvin mined the depths of the fathers, he took them in a direction that they didn’t go in the type of explicit ways that he took them; that is with reference to ‘knowledge of God as Redeemer’ vis-à-vis ‘knowledge of God as Creator.’ As an extension of this constructive reception on Calvin’s part, that is of the implications provided for by the fathers, Barth constructively receives Calvin’s insights and applies them in a Christ concentration that Calvin only provided for in an incipient way. The material point of the matter is that as Barth has underscored, to know what creation is about we first must know who the Creator is; and the only way we can do that, according to Barth, and more importantly, according to Holy Scripture, is to understand that Christ is the ‘firstborn from the dead.’ That is to say, to understand that creation’s ultimate telos has always already been the Christ, as David Fergusson aptly notes: “the world was created so that Christ might be born.” It is this type of patristic theo-logic, to think God as Son of the Father (per Athanasius), that Barth is appealing to, and pressing Calvin into his services in this way; such that to think creation rightly, according to Barth, is to first think the ‘Son of the Father’ in Jesus Christ. It is as we are confronted with this effervescent reality of God’s life come with hair, toenails, flesh and blood, that creation comes to life, just as sure as the Son of Man fell into the ground as a seed, died, and sprung to life in the greenness of new creation, as the consummation and ground of creation’s final existence and reality. And it is union with Christ (unio cum Christo) by the Spirit that the ontological ground of creation, as that comes as a prius for us in Jesus Christ, gives epistemological life for us as we see the face of God, and thus creation’s ultimate reality, in Jesus Christ’s vibrant smile for us.
The moral: to attempt to think God from nature, from a natural theology, and in extension, as natural law, is to think a projection of ourselves into the vestiges of creation and name those vestiges Father, Son, and Holy Spirit. This is to say, it is idolatry to attempt to think God outwith principially thinking Him from the evangelical contours of His life for the world in the fullness of life for us in Jesus Christ. It is only as we repose in this analogia relationis (‘analogy of relation’) that has eternally co-inhered between the Father and Son by the Holy Spirit, that we have any hope of knowing the God who has eternally inhabited the supra-physical reality of His triune life of plenitudinous joyousness.
There are many today, particularly those attempting to resource the scholastics Reformed of the 16th and 17th centuries, respectively, who are introducing the evangelical churches to a god connived from speculative categories; as if God might be known and grammarized in the abstract ways we noted earlier. They would have people think that God is a monad, and our only hope for knowing Him is if first he elected us individually (so the decretum absolutum), and then secondarily, as a result of being one of His ‘elect’ we might come to have capacity to observe Him as His vestiges of infinitude, eternality, and immutability lay latent on the soil of the earth and atmosphere of the heavens, as those are discovered by our powers of abstract rationales and creativity. Indeed, I may have misspoke, even the pagan philosophers, like Plato and Aristotle, according to these ‘resourcers,’ have the capacity to see God’s vestiges in the creation, what they require, and what only the elect of God have been gifted with is a superadditum of ‘grace perfecting nature,’ of ‘revelation perfecting reason,’ such that the theologian can finally make the leap from God’s effects in the created order to their final cause and repose in the Unmoved Mover of actus purus (‘pure being’) who they name Father, Son, and Holy Spirit. Barth is countering this; he is putting Calvin to work to counter this; and he is intimating that certain church fathers are odds with this type of ‘classical theistic’ reasoning that would attempt to think creation, and thus its Creator, in abstraction from the primacy of Christ, and our union with Him as the ground and basis for a genuine knowledge of the genuine and living God in Jesus Christ.
Be Blessed
[1] Karl Barth, Church Dogmatics III/1 §40 [031] The Doctrine of Creation: Study Edition (London: T&T Clark, 2010), 30.
[2] Ibid., 30-1. [italics mine, they represent the translation of Calvin’s Latin]