Systematic Theology and Historical Theology

I want to continue my look at Systematic Theology. In this post I will be considering the relationship between Systematic Theology and Historical Theology. I want to bring to light two major approaches to Historical Theology. The first approach is that it can be studied by schools or in a given period of time in history. In other words, this approach to theology is called the Synchronic approach.
The second approach is to trace the history of thought regarding a particular doctrine. This type of approach is called a diachronic approach. Now having these two approaches in the front of our minds we can begin to look at the need for this type of theology. As a philosopher I think Historical theology does a wonderful Job at making us aware of our own presuppositions. It has been stated by many people many times that Ideas are what move men to action. So in the context of theology it seems safe to assume that we did not get to where we are theologically by mere chance. Instead through out the history men have struggled with extrapolating a proper view of God, Christ, and man, as well as God's relationship to his creation. So in short one of the major values of Historical theology is to help us understand why we believe the way we do. The second value of historical theology is that it provides us with a grid in which to evaluate particular ideas that may arise in our time. What I mean by that is that if you hear a theology that stands in the face of Church history you better be able to show good evidence for it.
I want to give a warning here, I am not saying that tradition is the primary way of finding the truthfulness of a doctrine, but I am saying that it is part of the the grid.