Good quote here from John Frame (author of an excellent introduction to systematic theology):
We need a clearer understanding of what theology is. Many, I think, regard theology as discovering something within the Bible, sometimes called a “system.” On this view, the challenge of theology is to see who can reproduce this system in the fullest detail. In our circles, many assume that Calvin and the Westminster Standards did it best; they got the system right. So our theology must be a reproduction of theirs. This concept of theology encourages, I think, the “golden age” view of things and the necessity of holding rigidly and in detail to past models.
Let me suggest instead that the work of theology is the work of application. It takes the Scriptures and uses them to answer our present questions and to meet present needs. This is Paul’s concept of doctrine: teaching that is sound (health-giving) (1 Tim. 1:10, 6:3, 2 Tim. 4:3, Tit. 1:9, 2:1). Thus, as Jones says, its focus is upon the present and future, not only the past. And so theology is bound to the mission of the church.
Read the whole thing.
(As an aside, Frame really needs to start publishing these articles directly to his blog!)