John Webster offers too good of a sketch on a theory of revelation for me to simply pass it by without sharing it for you (and I’ll be using it in my doctoral study as well—which my topic has changed already, I’ll share what it is in an addendum at the end of this post). He synopsizes what I have often been after in many of my posts on the same locus. Let’s 
read along with him, and then I’ll close with some concluding reflections (and that addendum).
The broadest outline of a diagnosis would be something like this: For a good deal of the history of Christian theology before the modern era, the concept of revelation (whether explicitly articulated or, more often, merely implied is usage and patterns of argument) has its place as a part of a larger framework of convictions about God and God’s relation to human persons. Although the concept is often associated with ideas of “veil-lifting,” it is primarily concerned not with the communication of esoteric information but with the disclosure by God of God’s character, purposes for, and requirements of humanity. So construed, the notion of revelation thus implies that knowledge of the being and ways of God is God’s own gift, not the fruit of human creativity or searching. Because it is revealed, knowledge of God is the gift of divine grace and participation in God’s self-knowledge. Further, in characterizing God as the giver of knowledge of God, the concept of revelation thereby also characterizes human persons as recipients (rather than producers) of such knowledge. Accordingly, revelation and faith are closely correlated: faith is the anthropological counterpart of revelation. “Faith” is here understood not as mental assent but as trustful, receptive disposition of the self toward the self-disclosure of an agent beyond the self. The loci of such self-disclosure are variously identified as, for example, inner illumination, Holy Scripture heard as God’s Word, or the authoritative tradition of church teaching. All such loci are, however, conceived as relative to God’s supreme self-disclosure in and as Jesus Christ, and to the activity of God the Holy Spirit in enabling perception of and response to God’s gracious gift of knowledge of God. Understood in this way, the concept of revelation, classically conceived, is more than an epistemological category, furnishing a foundation for subsequent Christian belief. Revelation does not just answer the question of how claims to knowledge of God can be authorized; rather, it is a consequence of prior convictions about the prevenience of God in all God’s relations with humanity.
With the rise of fundamental theology and philosophical prolegomena to theology in the early modern period, this coinherence of the conception of revelation with grace, Spirit, and faith began to disintegrate. The Enlightenment critique of revelation was prepared in some measure by Christian theology itself, when natural philosophy was granted the task of establishing on nontheological grounds the possibility and necessity of revelation. The effect of this development was to loosen the bonds which tie the concept of revelation to its home in the dogmatic structure of Christian theology or even to sever the bonds altogether. This happened as the notion of revelation was redeployed, being assigned a job in apologetics or foundations. This “shift from assumption to argument” is also associated in some measure with the rise of scholastic styles of theological systematization in both Protestant and Roman Catholic circles. More particularly, increasing reliance on Aristotelian methods of argumentation and the quasi-Cartesian search for indubitable certainty in theology did much to undermine the correlation of revelation and faith. In effect, revelation shifts from being an implication of Christian conviction to furnishing the grounds from which Christian conviction can be deduced.[1]
The difference as Webster slices it: premodern/precritical = confessional; modern (with certain scholastic incipient antecedents) = apologetical. I think this represents a nice concise synopsis of the general prolegomena present within the history vis-à-vis a theory of revelation. I will simply leave it for your edification.
Addendum: As I have consulted further with my doctoral guide I will be writing, most likely, on the theologies of Bruce McCormack juxtaposed with Eberhard Jüngel’s respective readings of Karl Barth’s Christology and the implications of that for Divine freedom in the trinitarian being. So, it will really be a post-Barthian endeavor, in fact. I have read in this area, as well, for many years. But I will have to bone up further on Jüngel, who I have read, but not fully like McCormack, and it has been some years since I broke a page on one of his books or essays. Anyway, this should be fun!
[1] John Webster, The Culture of Theology, edited by Ivor J. Davidson and Alden C. McCray (Grand Rapids, Michigan: Baker Academic, 2019), 119-20.