Biblical theology is the sub-discipline of Christian theology that aims to understand and synthesize what scripture, or the Bible, tells us about God and other theological topics. As such, biblical theology is primarily distinguished from other types of theology by the methodology it uses to draw its conclusions. Specifically, the method of biblical theology exclusively focuses on the study and interpretation of scripture.
Biblical theologians may focus on one part of scripture—e.g., the New Testament, or the Old Testament (i.e., the Hebrew Bible)—or they may take all of scripture as their source of theology. George Eldon Ladd’s A Theology of the New Testament is a famous example of New Testament theology, while John Goldingay’s three volume Old Testament Theology is an excellent recent example of Old Testament theology.
To gain a clearer understanding of what biblical theology is it will be helpful to try to distinguish it from systematic theology. The two theological sub-disciplines are distinct in several ways.
Scripture: The Only Source of Biblical Theology
First, the methodology of biblical theology (noted above) makes it distinct from systematic theology. While many systematic theologians use the Bible as a source, most also draw on other sources in formulating their theology. For example, in formulating a doctrine of creation—an account of how and why God created the world and its inhabitants—systematic theologians routinely draw on scientific data, such as the conclusions of astronomy and evolutionary biology (e.g., see Hans Schwarz’s Creation). Similarly, in formulating a doctrine of human nature, a systematic theologian might well draw on the conclusions of recent neurological science that bear on whether human beings have a soul distinct from the body. These scientific sources are not used by biblical theologians, who restrict themselves to a description of the theology evidenced in Scripture, except insofar as such sources help with biblical interpretation.
Biblical Theology as Descriptive
Second, biblical theology is distinct from systematic theology in that it does not necessarily take up questions of what is true or false about various theological topics. Whereas systematic theology asks the question, “What is true of such and such theological topic?”, biblical theology asks the question, “What does the Bible say about such and such topic?” Or, if we want to be more careful, biblical theology asks, “what does the NT say, or what does John say, or Paul say?” The point of biblical theology, then, is to determine the distinctive elements of each collection, book, or author. Biblical theology is thus analytical and descriptive; questions of truth or falsehood, or of the relevance or irrelevance of various topics or conclusions are not necessarily central.
While a biblical theologian might be committed to the view that what Scripture teaches is true and relevant—in which case she might take the conclusions she draws about the theology of the Bible to be true and relevant—she also might not take this view, and so she might not take her conclusions to be true or relevant as such (though she probably takes them to be true conclusions about what the Bible teaches). In the first instance, then, the point of biblical theology is simply to analyze and describe. Going further to ask questions about the truth or falsehood of biblical theological claims—and in what sense such a claim might be true or false—leads to new ground. Such an approach pushes outside of biblical theology and toward systematic theology.
Biblical Theology and the Topics of Scripture
Third, the range of topics addressed by a biblical theologian is narrower than the range addressed by a systematic theologian. For the biblical theologian, the Bible sets the range of topics to be discussed. If the Bible takes up the topic, then so must a biblical theology; if the Bible does not take up the topic, then biblical theology has nothing to say on the matter.
For example, the recently controversial theological topic of the inerrancy of Scripture is not, itself, in the Bible; it is extra-biblical. (Of course, the inspiration of Scripture is addressed in the bible, though inspiration is different from inerrancy.) Thus, the inerrancy of Scripture is not, strictly speaking, a topic of biblical theology. Rather, the topic of the inerrancy of Scripture is one that certain systematic theologians considered in an attempt to respond theologically to modern questions that are not directly addressed by Scripture, such as the extent to which Scripture is a reliable source of historical and scientific truth.
Biblical Theology: The Meadow and the Greenhouse
Finally, it may be helpful to distinguish biblical and systematic theology by way of an analogy. Flowers may grow both in a natural meadow and in a human-made greenhouse. In the meadow we tend to see more variation; we might even see particular flowers that don’t fit the ordinary characteristics of a species (e.g., an albino flower). However in the greenhouse, the flowers tend to be much more uniform. Biblical theology might be compared with flowers growing in the meadow: we might come across exceptional biblical claims that seem not to fit neatly with the message of other parts of scripture. Thus, biblical theology can be somewhat messy or untidy, especially since the Bible was written by many different authors during very different time periods. Systematic theology, on the other hand, is more like the greenhouse flowers: systematic theologians are in the business of synthesizing a single coherent viewpoint that is not as sensitive to exception and variation.