What is a mortal sin? The three conditions

A mortal sin is a serious sin that turns you away from God and cuts off the life of grace in your soul. For a sin to be mortal, three conditions must all be true at once: the matter is grave, you know it is seriously wrong, and you freely choose it anyway (CCC 1857). If one is missing, the sin is not mortal. And every mortal sin can be forgiven, ordinarily in Confession.

What does "mortal sin" mean?

"Mortal" means deadly. The Catechism says mortal sin "destroys charity in the heart of man by a grave violation of God's law" (CCC 1855). It is a choice against God's love, serious enough to break your friendship with him. Scripture itself distinguishes "sin which is mortal" from sin which is not (1 John 5:16-17).

Venial sin is different. It wounds that friendship but doesn't break it. Charity stays alive in you. Most of the everyday failures people bring to Confession, like impatience, small lies or a lazy prayer life, are venial. Our page on mortal vs venial sin compares the two side by side.

What are the three conditions for a mortal sin?

The Catechism defines mortal sin as sin "whose object is grave matter and which is also committed with full knowledge and deliberate consent" (CCC 1857). All three conditions have to be met together.

1. Grave matter

The act itself is seriously wrong. The Ten Commandments spell out what grave matter is (CCC 1858). Some sins are serious by their nature. Others depend on degree: stealing a pen from work isn't the same as stealing someone's savings.

2. Full knowledge

You know the act is sinful and against God's law (CCC 1859). This doesn't require a theology degree. It means you understood, at the time, that this was seriously wrong.

3. Deliberate consent

You chose it freely, as a real personal decision (CCC 1859). A thought that flashes through your mind, or something done half asleep or under real pressure, is not the same as a calm, free choice.

What counts as grave matter?

Examples include murder, adultery, sex outside marriage, pornography, missing Sunday Mass on purpose without a serious reason, serious theft, perjury, and receiving Communion knowingly in mortal sin. We go through the commandments one by one, with examples, in our list of mortal sins.

Remember that grave matter alone doesn't make a mortal sin. A person can do something gravely wrong without full knowledge or full freedom. The matter is serious either way, and it's still good to confess it.

What reduces culpability?

The Church is realistic about human beings. Your responsibility for an act "can be diminished or even nullified by ignorance, inadvertence, duress, fear, habit, inordinate attachments, and other psychological or social factors" (CCC 1735). Ignorance you couldn't help, strong feelings and passions, outside pressure, and psychological conditions can all reduce how guilty you are (CCC 1860).

• Habit and compulsion. A long-standing habit, like pornography, can weaken freedom. That doesn't make the act good, and it's still matter for Confession. But it's one reason the Church entrusts judgment to God.
• Fear and pressure. Acting under threat or real fear is not the same as acting freely.
• Honest ignorance. If you truly didn't know something was seriously wrong, and couldn't easily have known, your guilt is lessened.

There's an honest limit here too. Pretending not to know, or hardening your heart so you don't have to face the truth, doesn't lessen guilt. It increases it (CCC 1859).

What happens when you commit a mortal sin?

Mortal sin causes "the loss of charity and the privation of sanctifying grace, that is, of the state of grace" (CCC 1861). In plain words, the life of God in your soul is lost, though God himself never stops loving you or calling you back.

The Catechism is honest about the stakes: if a mortal sin is not redeemed by repentance and God's forgiveness, it causes exclusion from Christ's kingdom and the eternal death of hell (CCC 1861). That's why it matters. The Catechism also calls mortal sin "a radical possibility of human freedom, as is love itself": God takes your choices seriously because he made you free. But the same paragraph adds that while we can judge an act to be gravely wrong, "we must entrust judgment of persons to the justice and mercy of God." You can say an act is grave. Only God knows the heart of the person who did it, including your own.

In practice, someone aware of mortal sin should not receive Communion before going to Confession (CCC 1385). You can and should still go to Mass.

How do you come back from a mortal sin?

1. Tell God you're sorry, right away. Don't wait for Saturday. If your sorrow comes from love of God and includes the intention to confess as soon as you can, it already obtains forgiveness of mortal sins (CCC 1452). Our guide to perfect and imperfect contrition explains how.
2. Go to Confession. This is the ordinary way back. Confess every mortal sin you're aware of, by kind and roughly how many times (Code of Canon Law, can. 988). Imperfect sorrow, even sorrow that comes mainly from fear, is enough when you go to the sacrament (CCC 1453).
3. Receive absolution and do your penance. The priest's absolution restores the state of grace. Then you can receive Communion again.
4. Make a plan for next time. Think about what led you there, and what you could avoid or change.

What if I'm not sure whether it was mortal?

Confess it anyway, and say you're not sure: "Father, I don't know if I fully consented to this." That's a normal thing to say, and the priest will help you sort it out. You don't need to weigh every condition perfectly before you go.

If you find yourself worrying about mortal sin constantly, checking and re-checking, that may be scrupulosity. Tell your confessor, and follow his guidance even when your feelings disagree. Fear is not proof of guilt. A conscience that is anxious all the time needs peace and a steady guide, not more lists.

God's mercy is bigger than any mortal sin

There is no sin so grave that the Church cannot forgive it, as long as you repent (CCC 982). The father in the parable of the prodigal son didn't wait for a speech. He ran to meet his son (Luke 15:20). If you think you've committed a mortal sin, look up the next confession time at your parish, write down what you need to say, and go. The priest has heard it before, and he is glad to see you.