Systematic theology constructs a well-thought-out worldview that enables the church rightly “to think God’s thoughts after him” and to set biblical truth over against its worldview competitors. The goal of systematic theology is “to bring every thought captive to Christ” (2 Cor. 10:1–5) for our good, for the life and health of the church, and most significantly for God’s glory.

Before we can understand why systematic theology is essential, we must first understand what it is. There’s no single definition of systematic theology, but at its heart it’s the discipline captured by the phrase “faith seeking understanding.”

Systematic theology builds on the results of biblical theology. Biblical theology is the exegetical discipline that seeks to grasp the entirety of Scripture as the unfolding of God’s plan from Genesis to Revelation. Starting with Scripture as God’s Word written through human authors—our final authority (sola scriptura) for what we think about God, ourselves, and the world—biblical theology seeks to “put together” the entire canon in a way that’s true to God’s intent.

Systematic theology then applies the truths gained in biblical theology to every aspect of our lives. It leads to doctrinal formulation—what we ought to believe and how we ought to live—warranted by the canon and done in light of historical theology.

In this way, systematic theology constructs a well-thought-out worldview that enables the church rightly “to think God’s thoughts after him” and to set biblical truth over against its worldview competitors. The goal of systematic theology is “to bring every thought captive to Christ” (2 Cor. 10:1–5) for our good, for the life and health of the church, and most significantly for God’s glory.

Here are four critical things we can’t do without systematic theology.

1. Know God

Systematic theology is necessary to know God rightly as the triune Creator-covenant God (and nothing is more important than this!). It’s true that God has revealed himself in creation, and we know him from what he has made (see Ps. 19:1–6; Rom. 1:18–32). But God didn’t create us to know him merely from our study of creation; he spoke to us in words through the prophets and ultimately through our Lord Jesus and his inspired words through his apostles (John 1:1–18; 2 Tim. 3:16–17; Heb. 1:1–2; 2 Pet. 1:20–21).

But to know God truly we must know not only all of Scripture but also how to “put together” (by theological formulation) all that Scripture teaches.

For example, think of God as triune. The doctrine of the Trinity is true to Scripture, but it’s also the result of careful reflection on all that Scripture teaches about God’s oneness as God and threeness as Father, Son, and Spirit, plus much more. The Trinity isn’t found in one verse or chapter but in the entirety of Scripture, and unless systematic theology is done correctly, we won’t know God rightly.

Or think of the divine sovereignty-human freedom relationship. Careful theological reflection on the entire canon is necessary in order to get this truth right, which matters greatly in our daily lives.

Apart from theology, our grasp of who God is and even our trust of him in this fallen world will be less than what it should be.

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