Theology is the doctrine of God. Systematic theology is the presentation, in a systematic form, of that doctrine. But the doctrine of God, in the very nature of the case, is related to everything that enters into our knowledge. All our world depends upon Him and, hence, it follows that a systematic presentation of the doctrine of God involves a general view of the world through God. It must contain the ideas and the principles which enable us to look at our lives and our world as a whole and to take them into our religion instead of leaving them outside.
What, however, we have specially to deal with is not theology, but Christian theology – that knowledge of God which belongs to us as Christians and which is traced back to Christ. We know that Christ claimed to possess a unique and perfect knowledge of God and to impart that knowledge to His disciples. If we are really Christians, we must be sharers in it. We must know God. And our task, when we theologize, is to define our knowledge, to put it in scientific and systematic form and to show, at least in outline, that general view of the world which it involves. The Christian religion, it has been said truly enough, is not a revealed metaphysic. Still less is it a revealed natural science. Nevertheless, the Christian mind which would understand the truth which it possesses – which would not keep its religious convictions in one compartment of the intelligence and all its other operations in others – must not be afraid of as much metaphysics as is implied in this general view of the subject.
From: Studies in Theology: Lectures Delivered in Chicago Theological Seminary by James Denney (London: Hodder and Stoughton, 1895), pp. 1-2.