"And he, when he is come, will convict the world of sin."
Of what form of sin? Not of those social offenses called crimes, violations of the precepts and prohibitions of the Decalogue, the basis of the criminal code in all civilized countries. Human courts are competent to convict of crime. Nor does the Spirit convict of those injuries to ourselves known as vices, moral delinquencies not named in the Ten commandments. Conscience is sufficient to convict of these, aided by self-love and self-respect. But human law and conscience combined cannot eradicate evil from the heart. Philosophy has tried it and failed. Poetry, especially comedy and satire, have ineffectually attempted to convict the world of sin in all past ages. They have chastised cutaneous sins, denouncing the drunkard, the glutton, the opium user, the fornicator. All these were self-condemned before the shaft of ridicule was hurled at them. Each of them could say:
"I see the right, and I approve it too;
Condemn the wrong, and yet the wrong pursue."
But is not God's law thundering from Sinai a sufficient witness to convict of sin? No, it never did convince the world that sin is evil per se, a thing to be abominated, to be abhorred and shunned because of its inherent hatefulness and unspeakable vileness. The divine law is effectual only as it causes sin to be dreaded and avoided merely because of the punishment which will surely visit it.
There is needed more than an accuser and punisher of sin, a power which can not only probe and search the heart and turn it inside out, exposing to the sunlight all its loathsome leprosies, but a power which can effect a radical cure. The sinful heart needs a surgeon so sharp-sighted as to detect this deadly disease under all its disguises of euphonious names, and a physician so skillful as to apply an effectual remedy.
That healer of the sinful soul is the divine Comforter, mercifully sent, not to torment the world by forbidding its pleasures, but to bless the world by turning it away from its iniquities. Sins of every kind are the fruit of an invisible root to which they bear no outward resemblance. This root is too subtile for human laws and courts to see. It requires anointed eyes. No human philosophy had ever found the sum and substance, the poisonous essence of sin, in unbelief.
How can this be the all-inclusive sin? Is not historic doubt respecting persons and events innocent and even commendable? To such questions of a shallow rationalism we answer that unbelief in respect to Christ is more than withholding intellectual assent to a historic record. It is ingratitude towards a Benefactor and Saviour, and rebellion against a rightful Ruler, a refusal to bow the knee to the personal revelation of God. The cause of this unbelief is not intellectual, arising from a lack of evidences, but moral, arising from a lack of willingness. Christ is rejected because He lays the axe at the root sin, plants a hedge of thorns across the path of sinful pleasure, and kindles a consuming flame in the house of the worldling's idols. The Holy Spirit convicts unbelievers of a lie when they pretend that their unbelief toward Christ is merely honest doubt. It is because faith in Him draws after it what is conceived to be the unpleasant obligation to obey Him, that they are unbelieving. In fact, the Greek Testament has but one word for unbelief and disobedience. In truth and verity, however boldly and persistently the world may deny it, the fact is that unbelief in respect to Christ lies in the will so corrupt that it hugs sin and will not let it be taken away by the Son of God, who came into the world and submitted to the shame and agony of the cross for this very purpose.
— from The Gospel of the Comforter (1898) Chapter 6.