1 John 5:17 (RSV) explicitly differentiates a mortal sin from a less serious one: “All wrongdoing is sin, but there is sin which is not mortal” (KJV: “not unto death”).

Denying this would be tantamount to saying that a white lie or a momentary pang of jealousy or lust is the moral equivalent in God’s eyes of a torture, rape and murder. 

Everyone agrees that all sin is barred from heaven. This is precisely why purgatory is such a merciful, necessary doctrine. If God gets “serious” about actual, real sin in heaven, why in the world would He not start now? Catholics think that God — in practical terms — takes sin as seriously now as He will then, and that’s one reason why we think mere imputation or forensic declaration of holiness is a falsehood.

1 John 5:16 expressly contradicts Protestant teaching on this, stating, “God will give him life for those whose sin is not mortal.”But Protestants say “all sin leads to spiritual death,” and that all sins are equal in God’s eyes. Which are we to believe? 

The Apostle John is clearly making the distinctions we routinely make (when not wearing our “theological caps”) with regard to degrees of sin. Furthermore, it is not by any means certain from context that the “mortal sin” is blasphemy against the Holy Spirit alone. Some translations even have “there is sin,” rather than “there is a sin.”

The Bible provides several lists of sins that are said to prohibit one from entering “the kingdom of heaven”:

• 1 Corinthians 6:9-10 Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither the immoral, nor idolaters, nor adulterers, nor sexual perverts, [10] nor thieves, nor the greedy, nor drunkards, nor revilers, nor robbers will inherit the kingdom of God.
• Galatians 5:19-21 Now the works of the flesh are plain: fornication, impurity, licentiousness, [20] idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, party spirit, [21] envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God.
• Ephesians 5:3-6 But fornication and all impurity or covetousness must not even be named among you, as is fitting among saints. [4] Let there be no filthiness, nor silly talk, nor levity, which are not fitting; but instead let there be thanksgiving. [5] Be sure of this, that no fornicator or impure man, or one who is covetous (that is, an idolater), has any inheritance in the kingdom of Christ and of God. [6] Let no one deceive you with empty words, for it is because of these things that the wrath of God comes upon the sons of disobedience.(cf. Gal 1:8; Heb 12:16; Rev 21:8; 22:15). 

In other words, such lists presuppose serious distinctions among sins. Otherwise, if Calvinists are correct, these quite “Catholic” texts should have stated – without the specificity – “all sins bar one from heaven.”

This very day, I was wandering Facebook (bored) and came across a Reformed Protestant stating that “there are no degrees of sin. Sin is sin.” I submit that this is plainly and clearly unbiblical. Scripture in fact provides several indications of differences in seriousness of sin and also in subjective guiltiness:

• Matthew 5:22 But I say to you that every one who is angry with his brother shall be liable to judgment; whoever insults his brother shall be liable to the council, and whoever says, “You fool!” shall be liable to the hell of fire.
• Luke 12:47-48 And that servant who knew his master’s will, but did not make ready or act according to his will, shall receive a severe beating. But he who did not know, and did what deserved a beating, shall receive a light beating. Every one to whom much is given, of him will much be required; and of him to whom men commit much they will demand the more.
• Luke 23:34 And Jesus said, “Father, forgive them; for they know not what they do.” . . .
• John 9:41 Jesus said to them, “If you were blind, you would have no guilt; but now that you say, ‘We see,’ your guilt remains.”
• John 19:11. . . he who delivered me to you has the greater sin.
• Acts 17:30 The times of ignorance God overlooked, but now he commands all men everywhere to repent,
• Romans 3:25 . . . This was to show God’s righteousness, because in his divine forbearance he had passed over former sins;
• 1 Timothy 1:13 though I formerly blasphemed and persecuted and insulted him; but I received mercy because I had acted ignorantly in unbelief.
• Hebrews 10:26 For if we sin deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,
• James 3:1 Let not many of you become teachers, my brethren, for you know that we who teach shall be judged with greater strictness.

Some objectors to these notions bring up James 2:10: “For whoever keeps the whole law but fails in one point has become guilty of all of it.” Does this prove that all sins are the same; equally destructive and worthy of judgment? No; the passage is dealing with man’s inability to keep the entire Law of God: a common theme in Scripture. James accepts differences in degrees of sin and righteousness elsewhere in the same letter, such as 3:1 (above). James 1:12 refers to men who endure trial receiving a “crown of life.”

James also teaches that the “prayer of a righteous man has great power in its effects” (5:16), which implies that there are relatively more righteous people, whom God honors more (merit), by making their prayers more effective. He provided the prophet Elijah as an example. If there is a lesser and greater righteousness, then there are lesser and greater sins, because to be less righteous is to be more sinful, and vice versa.