Sola fide. Faith alone is the material principle of the Lutheran Protestant Reformation, and it is principial for the Reformed basis of knowledge of God and self. But because of classical metaphysics this principle didn’t blossom into the full flowered reality it had inherent to it in inchoate ways. In other words, because of an undeveloped grammar, because of the constraints presented by classical substance metaphysics, the idea of faith grounded in the kerygmatic reality (Evangelical reality) was moribund (I’ll have to leave at the level of assertion) in the sense that its full potential was not realizable until later developments.
Whether or not you agree with my assessment, and the sort of ‘retrieval’ I’m thinking of methodologically, David Congdon describes how faith alone as a material reality vis-à-vis the Gospel has resource to function in ‘critically’ ‘realistic’ ways in how we understood God and his relation to us through the Gospel (kerygma); how we understand the undertaking of theological discourse as that is objectively determined by the reality of God, and subjectively inhabited in human agents as they are in vicarious union with God’s subject for us in the humanity of Jesus Christ (that is some of my own interpolation, in regard to constructive thought based upon my reading of Congdon). Here Congdon has just finished some technical philosophical discussion in regard to developing what ‘correlation’ entails, particularly among French continental philosophy, and how grasping that helps us better locate the sort of dialectical theologies that both Barth and Bultmann operate from. For our purposes we will not engage with the technical philosophical discussion and instead engage with some of the conclusions of that as Congdon details its implications for us in the theologies of Barth/Bultmann (and dialectical theology in general).
What, then, is distinctively theological about the kind of strong correlationism that characterizes dialectical theology? Simply this: that the correlation is established and grounded in God. The action of God in the saving event of revelation is what creates the correlation between God and the human person. This correlation is faith, understood as a gift of divine grace. Unlike other objects, the object of faith is the divine subject, who is the active agent in the relation to humanity. The divine fides quae establishes the human fides qua. The human person does not have this correlation at her disposal but can only receive it ever anew. It is thus a kerygmatic correlation in that God constitutes the relation in and through the event of the divine word. A strong correlationism thus accomplishes what critical realism seeks to maintain—a real divine subject only accessible in and through this subject’s self-giving in faith—without the unnecessary and misleading baggage associated with the words “critical” and “realism.”
This is important because God is understood as the personal object and subject of theology, and the gift of himself that he gives us in Christ comes with a corollary reality for us in that faith becomes the most fitting locus by which knowledge of this God can be ascertained by. In other words, there is no prior intuition that a person can come by in regard to knowledge of the Christian God; there is no naked knowledge of God in this understanding of correlation, as if human beings possess some sort of latent capacity (created grace) for an abstract knowledge of God. No, in this frame there is a ‘correlative’ component between our theology (nostra theologia) and God, but it isn’t idealistically determined by a free-floating or presumed upon human agency in the world of nature. Instead, knowledge of God, regulated by the Gospel (kerygmatic) is only accessible through the mediating faith of Christ. As we are in union with Christ’s knowledge of God for us, as he is in the center of God’s life as Godself, the faith we think from in regard to God is itself a reality generated by the ground that this faith breaks into. In short: dialectical theology and the Reformed faith it offers, a kerygmatic correlationist type, is one that is particularly shaped not by the human agent, but by the God who has spoken (Deus dixit).
 David W. Congdon, The Mission of Demythologizing: Rudolf Bultmann’s Dialectical Theology (Minneapolis: Fortress Press, 2015), 422.