The laws of our nature are sure sooner or later to assert themselves, and constrain an opposite belief. A pendulum when at rest hangs perpendicularly to the horizon. It may by extraneous force be made to hang at any degree of inclination. But as soon as such force is removed, it is sure to swing back to its normal position. Under the control of a metaphysical theory, a man may deny the existence of the external world, or the obligation of the moral law; and his disbelief may be sincere, and for a time persistent; but the moment the speculative reasons for his disbelief are absent from his mind, it of necessity reverts to its original and natural convictions. It is also possible that a man’s hand may be so hardened or cauterized as to lose the sense of touch. But that would not prove that the hand in man is not normally the great organ of touch. So it is possible that the moral nature of a man may be so disorganized by vice or by a false philosophy as to have its testimony for the existence of God effectually silenced. This, however, would prove nothing as to what that testimony really is. Besides this, insensibility and the consequent unbelief cannot last. Whatever rouses the moral nature, whether it be danger, or suffering, or the approach of death, banishes unbelief in a moment. Men pass from skepticism to faith, in many cases, instantaneously; not of course by a process of argument, but by the existence of a state of consciousness with which skepticism is irreconcilable, and in the presence of which it cannot exist. This fact is illustrated continually, not only in the case of the uneducated and superstitious, but even in the case of men of the highest culture. The simple fact of Scripture and experience is, that the moral law as written upon the heart is indelible; and the moral law in its nature implies a lawgiver, one from whom that law emanates, and by whom it will be enforced. And, therefore, so long as men are moral creatures, they will and must believe the existence of a Being on whom they are dependent, and to whom they are responsible for their character and their conduct. To this extent, and in this sense, therefore, it is to be admitted that the knowledge of God is innate and intuitive; that men no more need to be taught that there is a God, than they need to be taught there is such a thing as sin. But as men are ignorant of the nature and extent of sin, while aware of its existence, until instructed by the Word of God, and enlightened by his Spirit; so they greatly need the same sources of instruction to give them any adequate knowledge of the nature of God, and of their relations to him.

Charles Hodge, Systematic Theology, Vol. 1, 199.