The main reason why I study Bonhoeffer is that while evangelicalism is still stuck in an epistemological dead-end Bonhoeffer provided a solution in 1929. Here’s a brief explanation of how Bonhoeffer’s solution works.
To have epistemology as a starting point for doing theology alsways means starting with the self, the question of the self, the transcendence of the self. Any knowing is a knowing by the self, with limits set by the self. It is the self who determines what can be known and thus it is the self who determines under what parameters object, the other, God can be known. Therefore, epistemology results in the self as the ground for knowing God and the self as the arbiter of revelation.
If we truly want to do theology properly we need to start with revelation. This can only be done in a situation in which epistemology and ontology are unified, in which ontology provides a proper basis for epistemology and epistemology allows for being to be its true self.
Dietrich Bonhoeffer thus develops his person-theology. Christ is the incarnation as person existing in the church. Through Christ revelation is provided for a present accessible ontology in the form of the church as the Body of Christ. The act of epistemology has access to that ontology not by starting rom the self (because that is the self turned in on itself) but through faith. The ontology of revelation is only accessible through faith. Act and Being are one in the encounter with Christ.
Thus Bonhoeffer explores the notion of the Person of Christ and the sociality of the Church in his person-theology which is also a theology of sociality.