What Is Biblical Theology?

In his justly praised and highly regarded Biblical Theology: Old and New Testaments, Geerhardus Vos tells us what biblical theology is: "Biblical Theology is that branch of Exegetical Theology which deals with the process of the self-revelation of God deposited in the Bible" (5).

Note well the key words "process" and "self-revelation." Process speaks to the temporal aspect of biblical theology, its unfolding of revelation across time. Self-revelation, which many rationalists will deny, speaks to how this unfolding of biblical theology is God's witness to himself and his ways in the history of the outworking of his redeeming love in the Son of God.

How does it differ, you might ask, from systematic theology? Vos tells us this as well, and does well in his telling of it:

Biblical Theology occupies a position between Exegesis and Systematic Theology in the encyclopaedia of theological disciplines. It differs from Systematic Theology, not in being more Biblical, or adhering more closely to the truths of Scripture, but in that its principle of organizing the Biblical material is historical rather than logical. Whereas Systematic Theology takes the Bible as a completed whole and endeavors to exhibit its total teaching in an orderly, systematic form, Biblical Theology deals with the material from the historical standpoint, seeking to exhibit the organic growth or development of the truths of Special Revelation from the primitive pre-redemptive Special Revelation given in Eden to the close of the New Testament canon (v–vi).

—Geerhardus Vos, Biblical Theology: Old and New Testaments (Carlisle: The Banner of Truth Trust, 1948).