In his book, Historical Theology, Geoffrey Bromiley notes that historical theology is neither simply church history, nor the history of theology. Rather, it is, itself theology. Historical theology, if it is to bear that name must be intelligible as being in and of itself a theological task. In other words, historical theology is itself actually a form of doing Christian dogmatics. It is not merely potential subject matter for dogmatics, historical theology, if it is indeed theology, is an act of dogmatics.
What might this mean for how we understand the nature of historical theology? I have one tenative suggestion. At the very least viewing historical theology as theology means is that the persons, movements, and realities considered in historical theology must cease be viewed merely as subject matter or bits of data to by considered from the standpoint of history. Rather, historical theology is theologizing historically about historical realities. Thus, to write a theology of Martin Luther, for example, I must not simply recount what Marting Luther thought about theological topics, rather I must write about the theological reality that Martin Luther was and is. In other words, I am not writing a description of Luther’s theological beliefs, but I am in fact writing a theology of Luther. I am making normative theological statements about his reality as a theological person within the drama of the Triune God’s redemption of the world in Christ. For me to write a theology of Martin Luther in a true sense I have to make sense of his existence, work, and impact within the framework of the historical economy of salvation actualized in the death and resurrection of Christ.
For historical theology to be true to its character as theology it must, minimally, not be simply the recounting of the theological beliefs of past thinkers, but rather as theologizing in a historical mode, situating historical realities, persons, movements, and events within the theo-dramatic narrative of Triune God. This, of course makes historical theology a far less safe endeavor. It is inherently risky to speak about the theological reality and signficance of historical persons as persons within God’s economy rather than simply as thinkers with which to agree or disagree. The task of historical theology is bigger than that, it is to narrate history in a doxological and theological mode that is neither hagiography nor an exercise of a hermeneutic of suspicion. Historical theology dares to bring theology to bear on the church’s own history, subjecting its members to the judgment of theology just as the historical theologian seeks to place himself under the judgments of history. As such historical theology may be second only to biblical theology in its ability to be dangerous, to oneself and others and should only be entered into with much trepidation.