It is written in the prophets — “They shall be all taught of God” — everyone of His children shall be brought to the knowledge of the truth, and what they have been taught in the understanding shall be made practical, that it may have its proper effect upon the conscience. And this is answered when it comes under the authority and power of the Word of God, and faithfully accuses or condemns according to that unerring rule.
Conscience supposes the knowledge of some rule and it consists in comparing a man’s state or actions with that rule, in order to discover whether they agree with it, or not.
The rule is the Scripture, the whole revealed will of God, which is the unerring, and the only standard of right and wrong: for all Scripture is given by inspiration of God, and is profitable for doctrine, to teach the man of God what is truth, and to make him wise in it unto salvation. Fallen man has no means of discovering the will of God, but as it is revealed to him. He has no innate knowledge. He has no implanted principles. He is born as ignorant of God, and of the things of God, as a wild ass’s colt. His understanding is darkened, being alienated from the life of God, through the ignorance that is in him, because of the blindness of his heart. And he has no means in his own power of attaining any divine knowledge: for he cannot by searching, find out God. The world by its wisdom never did find Him out. The Hottentots know as much of Him as the Greeks and Romans did: indeed the natural man, let him be ever so wise, knoweth not the things of the Spirit of God, neither can he know them; because they are spiritually discerned.
The Scripture then is the only rule of right and wrong. Conscience has no direction but this rule. Neither ethics, nor metaphysics, no fancied light of dark nature, no lawless law of rebel nature, no human science, whether pretended to be implanted, or by the use of reason to be acquired, have any right to guide the conscience. These are blind leaders of the blind, they undertake what they are not only unfit, but what they have no warrant for. A number of felons in a jail may think what they will of their state. They may take it upon them to form a mock court, and to try one another. They may acquit or condemn as they please: but the Judge and the jury will pay no regard to their foolish proceedings. There is a word which is to try us at the last day, and by that we should try ourselves at present. It was revealed for this purpose. And when the revealed truth is clearly understood, then conscience is acting aright, if it finds a true verdict for God, either accusing, or else excusing, according to the direction of His unerring word.
— Extracted