Theology holds a chief place in human thinking. In a purely intellectual view no questions have greater interest for scientific and philosophic thought. Besides, our moral and religious sensibilities, the profoundest of our nature, contribute an intensity of interest peculiar to theological study. This does not mean that religious feeling is the norm or ruling principle of theology. This study has its intellectual cast, just as questions of science and philosophy. Any peculiarities of theology relate mostly to the character of its subjects and the sources of its facts. The study of these facts, the processes of induction, and the doctrinal generalizations are in the same intellectual mode which we observe in other spheres of truth. The Scriptures are rich in doctrinal material, but in elementary form; and it is only through a scientific mode of treatment that these elements can be wrought into a theology in any proper sense of the term. "The whole drift of the Scripture of God, what is it but only to teach theology? Theology? what is it but the science of things divine? What science can be attained unto without the help of natural discourse and reason?"
Before entering upon the formal treatment of any great subject the way should be prepared, and the subject itself be set in as clear a light as practicable. This is specially urgent in the case of systematic theology. The Introduction is for this end, and its attainment requires several things. The several forms of theology must be distinguished and defined. We shall thus reach a clearer view of systematic theology. The true sources of theology must be determined and mistaken sources set aside. As the doctrinal value of the Scriptures hinges upon the question of their divine original, the proofs of such an original must be fully recognized.