Short answer: In Roman Catholic teaching, a mortal sin is a grave sin committed with full knowledge and deliberate consent, and it breaks a person's relationship with God until it is repented of and forgiven. The Bible does speak of a "sin that leads to death" in 1 John 5:16, but the term "mortal sin" and the system of mortal and venial categories come from church tradition. Protestants share the seriousness of sin but do not use that framework.
In This Article
If you grew up Catholic, you probably know the phrase well. If you did not, you may have heard it in a film or from a friend and wondered what it means and whether the Bible backs it up. Some readers arrive frightened, worried that something they did last week has put them outside God's grace. I want to answer the question plainly and then say something about that fear.
I am an evangelical pastor, so I will state Catholic teaching in the way the Catholic Church itself states it, and then say how I read the Bible. Where we agree, I will say so, and where we do not, I will not pretend otherwise.
What Is The Difference Between Mortal And Venial Sin?
The Catholic Church divides sins by their effect on a person's relationship with God. A venial sin wounds that relationship but does not destroy it. A mortal sin, the Church teaches, destroys the life of grace in the soul; "mortal" here means death-dealing. The Catechism of the Catholic Church sets out three conditions that must all be present for a sin to be mortal:
| Condition | What It Means |
|---|---|
| Grave matter | The act itself is seriously wrong, such as murder, adultery, serious theft, apostasy, or grave dishonour to God. |
| Full knowledge | The person knows the act is seriously sinful when they do it. |
| Deliberate consent | The person freely chooses it; compulsion, fear, habit or illness can reduce or remove responsibility. |
That last point is often missed. A Catholic who is genuinely unaware of the gravity of an act, or who acts under overwhelming pressure, has not necessarily committed a mortal sin even if the matter is grave. The Church does not teach that everyone who has done a terrible thing is damned; it says only God can judge the heart.
People often ask for "the list of mortal sins." There is not one fixed list. Grave matter is generally taken from the Ten Commandments, and the New Testament passages that warn about those who practise certain sins will not inherit the kingdom of God (1 Corinthians 6:9-10, Galatians 5:19-21) are commonly cited as well. The famous "seven deadly sins" are something else: they are called capital sins because they are sources, or "heads," from which other sins flow. They are not by definition all mortal. I walk through them in the seven deadly sins.
Is Mortal Sin In The Bible?
The phrase is not. The idea has a root in one passage, which Catholic theologians have cited for centuries:
All wrongdoing is sin, and there is sin that does not lead to death.1 John 5:17 (NIV)
The verse before it speaks of a brother or sister who commits "a sin that does not lead to death," and says "there is a sin that leads to death" (1 John 5:16). From that, the tradition drew a line between sins that are deadly to the soul and sins that are not.
What does John mean? Honest scholars disagree. Some take "death" as spiritual death, which fits the Catholic reading. Some think it refers to apostasy, a settled denial of Christ, like the false teachers John writes against in the same letter. Others take it as physical death as a form of discipline, as in the Corinthian church (1 Corinthians 11:30). John does not hand us a list or a procedure. He tells us to pray for a brother who sins, and that is the heart of the passage.
Elsewhere, the Bible does speak of sin in terms of life and death. "For the wages of sin is death" (Romans 6:23). Yet in the same chapter Paul says that the gift of God is eternal life in Christ. And Jesus himself spoke of sins that are more serious than others, such as the "weightier matters of the law" (Matthew 23:23). My article on whether all sins are equal goes into that.
What Does Catholic Teaching Say?
According to the Catechism, mortal sin causes loss of charity (love for God) and sanctifying grace. If it is not repented of and forgiven, it brings exclusion from Christ's kingdom and eternal death in hell. The Church also teaches, and this is important, that the way back is open as long as a person lives.
The ordinary way back is the sacrament of Reconciliation, or confession. The penitent confesses mortal sins to a priest, expresses contrition, and receives absolution, which the Church teaches is Christ's own forgiveness given through his minister. Catholics cite John 20:21-23, where the risen Jesus breathes on the apostles and speaks of forgiving and retaining sins. A Catholic is expected to confess mortal sin before receiving Communion. The Church also teaches that "perfect contrition," sorrow out of love for God, can restore grace even before one reaches a priest, provided the person intends to go to confession.
Two further points come up in the questions people search. First, there is no sin a priest is unable to absolve in principle. A small number of very grave offences carry an automatic excommunication whose lifting is reserved to the Holy See or a bishop, but even those can be forgiven through the proper process. Second, the "one sin that cannot be forgiven" in Catholic teaching is persistent refusal to repent, which the Catechism links to the sin against the Holy Spirit in Matthew 12. I look at that in the unforgivable sin.
How Do Protestants View It?
Most Protestants reject the mortal and venial division, but not because they think sin is small. Their reasons are these.
First, the Bible treats every sin as an offence against a holy God. "For whoever keeps the whole law and yet stumbles at just one point is guilty of breaking all of it" (James 2:10). Second, the New Testament teaches that every sin deserves death, and that Christ bore the penalty for the sins of those who trust him, past, present and future. Third, Protestants hold that salvation is a gift received by faith, so a believer is not moved in and out of a state of grace each time he sins.
That does not mean any behaviour is fine. The New Testament warns that those who make a practice of sin, with no repentance, show that they never knew Christ (1 John 3:6). A settled, unrepentant pattern is serious. And Hebrews 10:26 warns about deliberately continuing to sin after receiving the knowledge of the truth. Reformed and Baptist believers read those warnings as marks of a false profession; Wesleyans and many Arminians read them as a real danger of falling away. Catholics read them as support for mortal sin. These are family arguments among serious believers.
As for confession, evangelicals take Scripture to teach that we can go straight to God:
there is one God and one mediator between God and mankind, the man Christ Jesus1 Timothy 2:5 (NIV)
We also confess to one another in the church for help and accountability (James 5:16; see confessing your sins to one another), but we do not believe a priest is required for forgiveness.
Can A Mortal Sin Be Forgiven?
Yes. On this, Catholics and Protestants agree, and I want you to hear it clearly. No tradition that takes the Bible seriously says a repentant sinner is turned away. Catholics say forgiveness comes through repentance and the sacrament. Evangelicals say it comes through repentance and faith in Christ. In both, the door is open.
The promise is in the apostle John's own letter, just a few chapters before the "sin that leads to death":
If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.1 John 1:9 (NIV)
If you are carrying something heavy right now, notice the verbs. The condition is confession, honest agreement with God that what you did was wrong, and the promise is that God is faithful and just to forgive. His faithfulness is the ground, not your feelings. If you fear you have committed an unforgivable act, the very fact that you care is a sign you have not hardened your heart. My page on whether God forgives all sins and how to repent will help you take the next step, and what the Bible says about forgiveness of sin says more.
Key Bible Verses About Mortal Sin
- 1 John 5:16: the passage behind the idea of a sin that leads to death
- 1 John 5:17: all wrongdoing is sin, but not all sin is of the same kind
- Romans 6:23: the wages of sin is death, but the gift of God is eternal life
- James 2:10: stumbling at one point makes us guilty before the whole law
- 1 John 1:9: confession and God's faithful promise to forgive
- 1 Timothy 2:5: one mediator between God and humanity
- Matthew 12:31: the sin against the Holy Spirit, which Catholic teaching ties to final impenitence
Frequently Asked Questions
What are the 10 mortal sins?
There is no official list of ten. Catholic teaching names grave matter in the Ten Commandments, such as murder, adultery, theft and idolatry. The seven capital sins (pride, greed, lust, envy, gluttony, wrath, sloth) are a different list, of vices that lead to other sins. See the 1 John 5:17 distinction behind it.
Is saying "Oh my God" a mortal sin?
Catholic teaching treats misuse of God's name as a sin against the Second Commandment, but a careless exclamation without deliberate intent to dishonour God is generally considered venial, because mortal sin needs full knowledge and deliberate consent. I cover it in Is Saying Oh My God A Sin?
Can you still go to heaven if you commit a mortal sin?
In Catholic teaching, a person who dies in unrepented mortal sin is separated from God. A person who repents, through sacramental confession or perfect contrition with the intention to confess, is restored. Evangelicals answer differently: believers are kept by Christ, though persistent unrepentance shows a faith that was never real.
Can I confess my sins to God instead of a priest?
Protestants say yes, citing 1 John 1:9 and the one mediator between God and humanity. Catholics hold that Christ gave the apostles authority to forgive sins in his name and that mortal sin should be confessed to a priest. Either way, honest confession to God is never wasted.
What is the one sin that cannot be forgiven in Catholicism?
Catholic teaching, drawing on Matthew 12, names sin against the Holy Spirit, which it describes as deliberately refusing to repent and accept God's mercy. It is not that God is unwilling to forgive; it is that the person will not receive it. See my article on the unforgivable sin.
