Gregg Allison discusses two approaches to historical theology. There are two basic approaches commonly found in historical theology: synchronic and diachronic.
“The synchronic approach engages in the study of the theology of a certain time period, a particular theologian, a specific theological school or tradition, and the like. Examples of this approach include the study of the doctrine of the Trinity in the third and fourth centuries, the development of Christology in the fourth and fifth centuries, the theology of John Calvin, and neo-orthodox theologies of the Word of God” (Gregg Allison, Historical Theology.[1] This is the method used by Alister E. McGrath in Historical Theology: An Introduction to the History of Christian Thought (click to open).
In addition to the synchronic approach, there is the diachronic approach which “engages in the study of the development of thought on a given doctrine throughout the periods of the church’s history. Examples of this approach include the study of the doctrines of Scripture and sin as developed in the early church, the Middle Ages, the Reformation and post-Reformation period, and the modern period.”[2] This is the approach of Gregg Allison in his Historical Theology (click to open).
Charles Ryrie noted the importance of Historical Theology: “A student can be more efficient in coming to his own understanding of truth by knowing the contributions and mistakes of church history.”[3]
[1]Alister E. McGrath, Historical Theology: An Introduction to the History of Christian Thought (Grand Rapids: Zondervan, 2011), 29, Kindle Edition).
[2] Ibid., 29.
[3] Charles Ryire, Basic Theology, (Chicago: Moody Press, 1999), 14.