By Clement Harrold
August 31, 2025
The Catholic Church teaches that there are two kinds of sin: venial and mortal. While venial sin offends and wounds charity in the soul, mortal sin destroys it. Mortal sin occurs when a gravely evil act is chosen with full knowledge and freedom. The Catechism defines it as “a grave violation of God’s law” which “turns man away from God, who is his ultimate end and his beatitude” (1855). The Catechism goes on to explain that the consequence of an unrepented mortal sin is exclusion from God’s Kingdom. But where does this doctrine appear in Scripture?
Sin That is Deadly
The distinction between venial and mortal sin is grounded in the biblical idea of gradations of sin. Indeed, Sacred Scripture clearly teaches that some sins are worse than others. Here are a couple of examples:
Whoever then relaxes one of the least of these commandments and teaches men so, shall be called least in the kingdom of heaven . . . “You have heard that it was said to the men of old, ‘You shall not kill; and whoever kills shall be liable to judgment.’ 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. (Matt 5:19,21-22)
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 12:47-48)
In these passages, Jesus draws a distinction between lesser and greater sins. Some sins merit “judgment,” while others merit “the hell of fire;” some sins deserve “a light beating,” while others deserve “a severe beating.”
Our Lord’s teaching on different levels of sin is repeated in 1 John, which provides the framework for what the Catholic Church teaches about mortal sin today:
If you see your brother or sister committing what is not a deadly sin, you will ask, and God will give life to such a one—to those whose sin is not deadly. There is sin that is deadly; I do not say that you should pray about that. All wrongdoing is sin, but there is sin that is not deadly. (1 John 5:16-17)
Here the sacred author clearly distinguishes between “sin that is deadly” (i.e. mortal sin) and “sin that is not deadly” (i.e. venial sin). Hence the Catholic doctrine of mortal sin is firmly grounded in Sacred Scripture.
The Consequences of Mortal Sin
One of the reasons Protestants often find the biblical doctrine of mortal sin uncomfortable is that it implies that even a baptized Christian can lose his or her salvation by falling into serious sin. And yet, it’s important to recognize that this is precisely what the Bible teaches. Consider the words God speaks through the prophet Ezekiel:
The righteousness of the righteous shall not deliver him when he transgresses; and as for the wickedness of the wicked, he shall not fall by it when he turns from his wickedness; and the righteous shall not be able to live by his righteousness when he sins. Though I say to the righteous that he shall surely live, yet if he trusts in his righteousness and commits iniquity, none of his righteous deeds shall be remembered; but in the iniquity that he has committed he shall die. (Ezek 33:12-13)
Ezekiel makes it very clear that the righteous man is still capable of the kind of transgression which leads to spiritual death. It’s also worth noting that Jesus Himself sees the keeping of the most important commandments as being essential to entering eternal life:
And he said to him, “Why do you ask me about what is good? One there is who is good. If you would enter life, keep the commandments.” He said to him, “Which?” And Jesus said, “You shall not kill, You shall not commit adultery, You shall not steal, You shall not bear false witness, Honor your father and mother, and, You shall love your neighbor as yourself.” (Matt 19:17-19)
Jesus’s words imply that breaking a commandment like “You shall not kill” or “You shall not commit adultery” will prevent a person from getting to heaven if he or she fails to repent of that sin. This line of thinking is echoed in St. Paul, who repeatedly reminds his Christian listeners that if they relapse into mortal sin, they will not enter the Kingdom of God:
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 homosexuals, nor thieves, nor the greedy, nor drunkards, nor revilers, nor robbers will inherit the kingdom of God. (1 Cor 6:9-10)
Now the works of the flesh are obvious: sexual immorality, impurity, debauchery, idolatry, sorcery, enmities, strife, jealousy, anger, quarrels, dissensions, factions, envy, drunkenness, carousing, and things like these. I am warning you, as I warned you before: those who do such things will not inherit the kingdom of God. (Gal 5:19-21)
But fornication and all impurity or covetousness must not even be named among you, as is fitting among saints. Let there be no filthiness, nor silly talk, nor levity, which are not fitting; but instead let there be thanksgiving. 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. (Eph 5:3-5)
There is no doubt in Paul’s mind that the gift of human freedom is such that we have the power to decisively turn our backs on God even after our baptism. We see this same point made throughout the Scriptures, including in the parable of the weeds, which warns us that we cannot presume upon our own salvation. Instead, we need to make our entire life a process of ongoing conversion whereby we continually deepen our resolve to turn away from sin and re-commit ourselves to Christ.
Mortal Sin and the Mercy of God
We’ve seen how the Bible clearly teaches the reality of mortal sin and warns all of us—including committed Christians—of its dangers. Yet the Bible also loudly affirms the extravagant love of a God who died for us while we were still sinners (see Rom 5:8). This is the same God who “desires all men to be saved and to come to the knowledge of the truth” (1 Tim 2:4) and who empties Himself out for the sake of His children, “not wishing that any should perish, but that all should reach repentance” (2 Pet 3:9).
If these verses tell us anything, it’s that God desires our salvation so much more than we do. We can therefore be confident that nobody is damned by accident. As the parable of the wedding feast beautifully reveals, God’s offer of salvation extends to all people, even the undeserving. At the same time, the parable warns us to avoid the presumptuous attitude of the guest who shows up at the heavenly feast refusing to wear the appropriate attire. That guest demanded that the dress code be conformed to his own standards and desires, and he was cast into the outer darkness as a result.
The parable of the wedding feast offers a sobering reminder that merely because we received an invite to the wedding, still our place at table is not guaranteed; through our self-centeredness, we can forfeit the invitation we have been given. Our only recourse, therefore, is to throw ourselves on the mercy of the Bridegroom, and to pray earnestly for that grace of final perseverance which will enable us to remain faithful to Him until the end (see Heb 10:19-39).
Further Reading
John Paul II, Reconciliatio et Paenitentia (1984)
Matthias Joseph Scheeben, The Glories of Divine Grace (TAN Books, 2023)
https://www.ncregister.com/blog/what-the-bible-says-on-degrees-of-sin-and-mortal-sin
About Clement Harrold
Clement Harrold earned his master’s degree in theology from the University of Notre Dame in 2024, and his bachelor’s from Franciscan University of Steubenville in 2021. His writings have appeared in First Things, Church Life Journal, Crisis Magazine, and the Washington Examiner.
