What is systematic theology?
The Bible is no more a system of theology, than nature is a system of chemistry or physics. We find in nature the facts which the chemist and physicist has to examine, and from them to ascertain the laws by which they are determined. So the Bible contains the truths which the theologian has to collect, authenticate, arrange, and exhibit in their internal relation to each other. This constitutes the difference between biblical and systematic theology. The office of the former is to ascertain and state the facts of Scripture. The office of the latter is to take those facts, determine their relation to each other and to other cognate truths, as well as vindicate them and show their harmony and consistency. This is not an easy task, or one of slight importance.
Why is systematic theology necessary?
It may be naturally asked, why not take the truths as God has seen fit to reveal them, and thus save ourselves the trouble of showing their relation and harmony?
The answer to this question is, in the first place, that it cannot be done. Such is the constitution of the human mind that it cannot help endeavoring to systematize and reconcile the facts which it admits to be true. In no department of knowledge have men been satisfied with the possession of a mass of undigested facts. And the students of the Bible can as little be expected to be thus satisfied. There is a necessity, therefore, for the construction of systems of theology. Of this the history of the Church affords abundant proof. In all ages and among all denominations, such systems have been produced.
Second, a much higher kind of knowledge is thus obtained, than by the mere accumulation of isolated facts. It is one thing, for example, to know that oceans, continents, islands, mountains, and rivers exist on the face of the earth; but it is a much higher thing to know the causes which have determined the distribution of the land and water on the surface of the globe; the configuration of the earth; the effects of that configuration upon climate, on the races of plants and animals, on commerce, civilization, and the destiny of nations. It is by determining these causes that geography has been raised from a collection of facts to a highly important and elevated science. What is true of other sciences is true of theology. We cannot know what God has revealed in his Word unless we understand, at least in some good measure, the relation in which the separate truths therein contained stand to each other. It cost the Church centuries of study and controversy to solve the problem concerning the person of Christ; that is, to adjust and bring into harmonious arrangement all the facts which the Bible teaches on that subject.
Third, We have no choice in the matter. If we would discharge our duty as teachers and defenders of the truth, we must Endeavour to bring all the facts of revelation into systematic order and mutual relation. It is only thus that we can satisfactorily exhibit their truth, vindicate them from objections, or bring them to bear in their full force on the mind of men.
Fourth, Such is evidently the will of God. He does not teach men astronomy or chemistry, but He gives them the facts out of which those sciences are constructed. Neither does He teach us systematic theology, but He gives us in the Bible the truths which, properly understood and arranged, constitute the science of theology. As the facts of nature are all related and determined by physical laws, so the facts of the Bible are all related and determined by the nature of God and of his creatures. And as He wills that men and women should study his works and discover their wonderful organic relation and harmonious combination, so it is his will that we should study his Word, and learn that, like the stars, its truths are not isolated points, but systems, cycles, and epicycles, in unending harmony and grandeur.
Besides all this, although the Scriptures do not contain a system of theology as a whole, we have in the Epistles of the New Testament, portions of that system wrought out to our hands. These are our authority and guide.
The above were selected from Charles Hodge, Systematic Theology, Volume I, Part 1, pages 1-3.
See also:
Gordon H. Clark, In Defense of Theology, Trinity Foundation, 1984.
Rousas J. Rushdoony, “The Necessity of Systematic Theology,” in Systematic Theology, Volume I, Chalcedon Press, pages 1-58.
Additional Thoughts
Challenge: For those who would argue that system in theology, ethics, or any other area of knowledge is not necessary are challenged to “prove the virtue of disjointed truths,” to quote from Gordon Clark in his Introduction to Christian Philosophy.