Someone once asked me why we need professional theologians.

Nowhere in Scripture are we admonished to remain at the milk level of our understanding of our faith. In fact, we are explicitly told to study and prove out that which we believe.

There are many that sincerely believe this or that, but sincerity is never the test of the validity of one's belief. Sincere people around the world have constructed idols from their beliefs and go off worshiping them. There are many that eschew any sort of appeal to the masters that have preceded us, thinking that they are able to discern complex doctrines by simply reading the Scriptures, or wrongly assuming anything men have written outside of the Scriptures is unworthy of study or consideration. Very few persons can lay claim to a solitary achievement of mastery of the complexities of doctrine--that is why we read the texts of those few while checking them against the Word of God.

The study of God, theology, is every Christian's calling in order that we may prove out our beliefs, be ready to defend them, and not bring shame to God.

Thus, theologians are something like grammarians than like scientists or detectives. Such theologians show us (from the Bible) how to think, and how not to think, about God, and thusly how to talk about Him. What we should say, and what we should not say. Such theologians do not control what we may say; they indicate the rules of intelligible speech.

For a brief introduction to theology, see:

What is Theology - Christian Forums

AMR