It is so called because it agrees in everything essential with the inductive method as applied to the natural sciences.
First, The man of science comes to the study of nature with certain assumptions. (1.) He assumes the trustworthiness of his sense perceptions. Unless he can rely upon the well-authenticated testimony of his senses, he is deprived of all means of prosecuting his investigations. The facts of nature reveal themselves to our faculties of sense, and can be known in no other way. (2.) He must also assume the trustworthiness of his mental operations. He must take for granted that he can perceive, compare, combine, remember, and infer; and that he can safely rely upon these mental faculties in their legitimate exercise. (3.) He must also rely on the certainty of those truths which are not learned from experience, but which are given in the constitution of our nature. That every effect must have a cause; that the same cause under like circumstances, will produce like effects; that a cause is not a mere uniform antecedent, but that which contains within itself the reason why the effect occurs.
Second, The student of nature having this ground on which to stand, and these tools wherewith to work, proceeds to perceive, gather, and combine his facts. These he does not pretend to manufacture, nor presume to modify. He must take them as they are. He is only careful to be sure that they are real, and that he has them all, or, at least all that are necessary to justify any inference which he may draw from them, or any theory which he may build upon them.
Third, From facts thus ascertained and classified, he deduces the laws by which they are determined. That a heavy body falls to the ground is a familiar fact. Observation shows that it is not an isolated fact; but that all matter tends toward all other matter, that this tendency or attraction is in proportion to the quantity of matter; and its intensity decreases in proportion to the square of the distance of the attracting bodies. As all this is found to be universally and constantly the case within the field of observation, the mind is forced to conclude that there is some reason for it; in other words, that it is a law of nature which may be relied upon beyond the limits of actual observation. As this law has always operated in the past, the man of science is sure that it will operate in the future. It is in this way the vast body of modern science has been built up, and the laws which determine the motions of the heavenly bodies; the chemical changes constantly going on around us; the structure, growth, and propagation of plants and animals, have, to a greater or less extent, been ascertained and established. It is to be observed that these laws or general principles are not derived from the mind, and attributed to external objects, but derived or deduced from the objects and impressed upon the mind.
A. The Inductive Method as applied to Theology.
The Bible is to the theologian what nature is to the man of science. It is his store-house of facts; and his method of ascertaining what the Bible teaches, is the same as that which the natural philosopher adopts to ascertain what nature teaches. In the first place, he comes to his task with all the assumptions above mentioned. He must assume the validity of those laws of belief which God has impressed upon our nature. In these laws are included some which have no direct application to the natural sciences. Such, for example, as the essential distinction between right and wrong; that nothing contrary to virtue can be enjoined by God; that it cannot be right to do evil that good may come; that sin deserves punishment, and other similar first truths, which God has implanted in the constitution of all moral beings, and which no objective revelation can possibly contradict. These first principles, however, are not to be arbitrarily assumed. No man has a right to lay down his own opinions, however firmly held, and call them “first truths of reason,” and make them the source or test of Christian doctrines. Nothing can rightfully be included under the category of first truths, or laws of belief, which cannot stand the tests of universality and necessity, to which many add self-evidence.
But self-evidence is included in universality and necessity, in so far, that nothing which is not self-evident can be universally believed, and what is self-evident forces itself on the mind of every intelligent creature.
Facts to be collected.
In the second place, the duty of the Christian theologian is to ascertain, collect, and combine all the facts which God has revealed concerning himself and our relation to Him. These facts are all in the Bible. This is true, because everything revealed in nature, and in the constitution of man concerning God and our relation to Him, is contained and authenticated in Scripture. It is in this sense that “the Bible, and the Bible alone, is the religion of Protestants.” It may be admitted that the truths which the theologian has to reduce to a science, or, to speak more humbly, which he has to arrange and harmonize, are revealed partly in the external works of God, partly in the constitution of our nature, and partly in the religious experience of believers; yet lest we should err in our inferences from the works of God, we have a clearer revelation of all that nature reveals, in his word; and lest we should misinterpret our own consciousness and the laws of our nature, everything that can be legitimately learned from that source will be found recognized and authenticated in the Scriptures; and lest we should attribute to the teaching of the Spirit the operations of our own natural affections, we find in the Bible the norm and standard of all genuine religious experience. The Scriptures teach not only the truth, but what are the effects of the truth on the heart and conscience, when applied with saving power by the Holy Ghost.