The gospel is a reasonable system, and it appeals to men's understanding; it is a matter for thought and consideration, and it appeals to the conscience and the reflecting powers। Hence, if we do not teach men something, we may shout, "Believe! Believe! Believe!" but what are they to believe? Each exhortation requires a corresponding instruction, or it will mean nothing. "Escape!" From what? This requires for its answer the doctrine of the punishment of sin. "Fly!" But whither? Then must you preach Christ, and His wounds; yea, and the clear doctrine of atonement by sacrifice. "Repent!" Of what? Here you must answer such questions as, What is sin? What is the evil of sin? What are the consequences of sin ? "Be converted!" But what is it to be converted? By what power can we be converted? What from? What to? The field of instruction is wide if men are to be made to know the truth which saves. "That the soul be without knowledge, it is not good," and it is ours as the Lord's instruments to make men so to know the truth that they may believe it, and feel its power. We are not to try and save men in the dark, but in the power of the Holy Ghost we are to seek to turn them from darkness to light.
Spurgeon on Doctrine
Thanks to Adrian Warnock for a quote from C. H. Spurgeon that is well worth repeating: