Theology names speech about God, and stands to faith as science to understanding

Theology, by the etymology of the word, means speech about God. Taken generally, it names every teaching that treats of God and of divine things. And because God can be treated of in two ways — first from principles known by the natural light, then from principles which God has made known in a supernatural manner — a twofold theology is commonly distinguished: one natural, the other supernatural.

Natural theology is that part of philosophy which treats chiefly of immaterial being and of God. Aristotle himself calls metaphysics by this name in the first book of the Metaphysics. Supernatural theology, however, is that teaching about God which has its origin from divine revelation. This theology is called theology absolutely and by antonomasia. It is of this alone that we must treat from here on.

Further, the habit that rests on revelation is twofold. One is that by which we simply believe and embrace what is contained in the word of God; and this habit is nothing other than faith itself. The other is that by which a person is fitted to explain distinctly the things that faith believes, to assert and defend them with various reasons, and from them to draw legitimate consequences. This habit is properly called theology.

Theology, taken in this way, stands to faith as science stands to understanding. For faith is the habit of the principles; theology is the habit of the conclusions. The primary and principal object of faith is certain truths immediately and expressly revealed by God. The proper objects of theology are those revealed only mediately and virtually — that is, those gathered by reasoning from those first immediately revealed truths. So theology, though distinguished from faith, still presupposes faith and in a way includes it. But faith does not necessarily bring theology along with it.