When we speak of theology as “theoretical” we are not speaking about something uncertain or non-factual.
The term “theory” comes from the Greek term theoria. It means “to contemplate.” Theoretical theology is what happens when we think, or contemplate, theologically. To put it more simply, theoretical theology is theology as it is known.
Theoretical theology is what we encounter while reading a system of theology, like Herman Bavincks Reformed Dogmatics or Thomas Aquinas’ Summa Theologiae.
Scripture itself witness to the place of theoretical theology. There is an emphasis through Scripture placed upon the knowledge of God.
In Psalm 100:3 we read, “Know that the LORD, He is God; It is He who has made us, and not we ourselves; We are His people and the sheep of His pasture.” In Colossians 1:9, the apostle Paul writes, “For this reason we also, since the day we heard it, do not cease to pray for you, and to ask that you may be filled with the knowledge of His will in all wisdom and spiritual understanding…”
In Colossians 1:10, the prayer is that the Colossian church would increase “in the knowledge of God…” And in Colossians 2:2, they would attain “to all riches of the full assurance of understanding, to the knowledge of the mystery of God, both of the Father and of Christ…” The apostle Peter greets his audience, saying, “Grace and peace be multiplied to you in the knowledge of God and of Jesus our Lord…” (2 Pet. 1:2)
While all these uses of knowledge certainly move beyond a mere theoretical apprehension of doctrinal facts, a theoretical grasp of theology must be received by the intellect before the same can affect the will of man.
To use a popular illustration: theology is “head knowledge” before it becomes “heart knowledge.”
Theoretical theology is theology as it is known by the creature. There is another way of considering theology as practice, or practical theology. If theoretical theology is known, practical theology is that same theology lived.