Theology is the study of God’s revelation for our edification. We may think of different ways of doing theology through various disciplines or branches. There is not necessarily one “correct” way of classifying theological branches. Generally what is meant by “branch” is a kind of doctrinal study—that is, the branches are concerned with what the Bible teaches. Falling under doctrinal studies would be biblical, historical, systematic, and philosophical theology.
Each branch provides its own unique flavor or fruitfulness for the theologian. It would be inappropriate to think of one branch as superior in value to the others. Instead, the branches function interdependently. For we could not do philosophical theology without systematic theology; we could not do systematic theology without biblical theology; and historical theology could not function without at least one of the other branches. I will define and further differentiate between them (plus two additional ones), which may in turn allow the reader to identify which branch is of most interest.
Biblical Theology
The best way to understand biblical theology is the study of an isolated biblical text in consideration of the overall biblical narrative. As such, it relies heavily on the works of biblical exegesis (original languages) and historical-cultural studies for interpretation. Biblical theologians will center their attention on an individual passage, book, author, or a particular grouping of books. Something to the effect of the “theology of Paul,” “theology of non-Pauline epistles,” or “theology of minor prophets.” The goal is to uncover the message and teachings of Paul or the non-Pauline epistles or the minor prophets (etc.) in relation to the entirety of Scripture. Biblical theology may serve as the foundation for the other branches.
Historical Theology
If we are to avoid making the same mistakes, theologians must account for the doctrinal beliefs held by the church throughout her lifetime. Such is the task for the historical theologian. This branch of theology is not so much interested in the doctrine of the Atonement, for instance, but what the church believed about the doctrine of the Atonement throughout her history. Its objective is therefore twofold: first, to understand what was believed by the church (or a particular theologian) at a certain point in history; and second, to show how the beliefs of the church (perhaps regarding a particular doctrine) have developed over time.
Systematic Theology
No doubt systematic theologians benefit from the fruits of biblical and historical theology. This branch of theology is all about systematically surveying, organizing, and articulating the biblical concepts. Essentially systematic theology aims to answer the question, “what does the Bible teach about…?” (e.g., sin, God’s attributes, love, forgiveness, salvation, angels). Taking forgiveness as an example, the systematic theologian would respond by citing and explaining a number of different passages across the various books of Scripture (Jer 31:34; Ps 32:5; Mic 7:18; Dan 9:9; Mt 6:14-15; Lk 6:37, 23:34; Col 3:13; Eph 1:7, 4:32; Jam 5:16; 1 Jn 1:9; and so forth).
Similar to biblical theology, systematic theology weighs the interpretation of various biblical passages. Unlike biblical theology, systematic theology is not as interested in the progressive biblical narrative as it is the chosen theological concept. Although perhaps not its intent, systematic theology also varies from the other branches in its tendency to provide practical application through its detailed description of theological concepts with practical implications (such as forgiveness). The overarching theme of systematic theology is to arrange coherent and structured explanations of theological concepts.
Philosophical Theology
Make no mistake, philosophical theology is first grounded in Scripture. The work of philosophical theologians is nearly identical to that of systematic theologians. Where this branch of theology differs is its openness to expand beyond what can be known in Scripture and into philosophical exploration. Take God’s relationship to time as an example. Despite what many theologians may state, and while we do have a number of passages worth citing on this topic (e.g., Gen 1:1; Ps 90:4; Is 57:15; 2 Tim 1:9; 2 Pe 3:8), the Bible does not provide a clear understanding of God’s relation to time—whether he is omnitemporal or timeless or otherwise. Therefore, if theologians are to construct a coherent and extensive view of God’s relationship to time, they must utilize the tools of philosophy. They do so by creating philosophical models of theological concepts. Take the doctrine of the Trinity as an example of a philosophical model. The Bible grants deity to three persons—Father, Son, and Holy Spirit—while also maintaining God oneness. Scripture does not give us much more than that, therefore we require the tools of philosophy to create models, such as “God is one substance and three persons” or “God is equipped with three sets of rational faculties.” Philosophy also helps elucidate theological terminology and improve clarity. In conclusion, philosophical theology seeks to give explanations of theological concepts that are insufficiently explained in Scripture or illuminates those that are sufficiently explained.
Natural Theology
Natural theology differs from the other branches as it is not doctrinal nor grounded in Scripture. If Scripture is utilized, the natural theologian will not consider it authoritative for the interest of their studies. Although it has much in common with philosophical theology, the two are distinct. Natural theology seeks to provide evidence for God’s existence using the tools of philosophy, science, and history. While natural theology is hardly concerned with what the Bible teaches, it is appropriate to think of natural theology as a branch of theology since it focuses on what we can know about God’s existence from divine general revelation.
Practical Theology
Practical theology reflects on the works of the other branches and applies its teachings to everyday Christian life. Practical theologians critically discern how theological knowledge can help live out the Christian virtues; and they subsequently evaluate how contemporary church practices match those theological truths. Since our definition of theology includes edification, this branch of theology should not be overlooked.
I included a chart of the different branches.
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