What is sin? The Catholic meaning of sin, and God’s mercy

What is sin? The Catholic definition

Sin is “an offense against reason, truth, and right conscience”: a failure in genuine love for God and neighbor, caused by a disordered attachment to some lesser good (CCC 1849). It is a free, deliberate act — a thought, a word, a deed or a failure to act — that we know to be against God’s law and choose anyway. That is the short answer to what is sin; the Church then fills it out.

Above all, sin is an offense against God. “Against you, you alone, have I sinned,” prays the psalmist (CCC 1850). Sin sets itself against God’s love and turns the heart away from it; the tradition even calls it “love of oneself even to contempt of God” (CCC 1850). It also wounds the one who sins and injures the whole human family, because no sin is ever truly private (CCC 1849).

What does the Bible say about sin?

In Scripture, the most common words for sin mean “to miss the mark” — to aim at the good and fall short of it. Sin is disobedience and a broken relationship, from the first refusal in Eden to the daily failures Saint Paul names in his letters. No one is exempt: the Bible’s diagnosis is universal before it is personal.

Scripture also shows the way back. Psalm 51 (50), prayed after King David’s sin, is the Church’s great prayer of repentance: the sinner does not hide, but turns to God and asks for a clean heart. The pattern runs through the whole Bible — honesty about sin, and trust in a mercy that is always greater. That is why naming sin clearly is never the end of the story.

Original sin and personal sin: what is the difference?

Original sin is not something you did. It is the wounded state of human nature that every person inherits from the first sin of our first parents, who abused their freedom and chose themselves over God (CCC 396–398). The Catechism is careful: original sin is called “sin” only by analogy — it is a state “contracted” and not “committed,” not a personal fault of yours (CCC 404–405).

Its effect is that human nature comes into the world weakened, ignorant, marked by suffering and death, and inclined to evil — an inclination the Church calls concupiscence (CCC 405). Baptism wipes away original sin, but the inclination remains, which is why life is a spiritual battle (CCC 405, 409). This is the ground on which personal sin grows.

Personal, or actual, sin is the sin you yourself commit by a free act (CCC 1849–1853). This is what the rest of this guide means by sin, and what you bring to Confession. It is measured by how serious it is — the difference between mortal sin and venial sin — and by the deliberateness of the choice behind it.

What are the kinds of sin? Thought, word, deed and omission

There are many kinds of sin, and Scripture itself gives several lists (CCC 1852). The Catechism sorts them in several ways: by the virtue they oppose or the commandment they break; by whether they concern God, neighbor or self; as spiritual or carnal; and, classically, as sins “in thought, word, deed, or omission” (CCC 1853). Whatever the form, the root of sin lies in the heart, in the free will (CCC 1853).

A sin of omission is the easiest kind to overlook: it is the good you knew you should do and simply did not. Scripture states it plainly, and the Confiteor has us confess our sin “in what I have done and in what I have failed to do.” Omission can be serious — ignoring someone in real need — or slight, but it belongs in an honest examination of conscience alongside what you actively did wrong.

Sin also reaches beyond the individual. Because we can share in others’ sins — by ordering, advising, praising or failing to prevent them — personal sins give rise to unjust situations and “structures of sin,” what the Church calls social sin (CCC 1868–1869). A structure of sin is still the fruit of personal choices; it is called social because of its effects, which draw others into evil in turn.

How serious is a sin? Mortal and venial

Sins differ in gravity, and the Church distinguishes mortal from venial sin — a distinction already present in Scripture (CCC 1854). Mortal sin destroys charity in the heart by a grave violation of God’s law and turns us away from God; venial sin wounds and weakens charity without breaking our friendship with him (CCC 1855).

For a sin to be mortal, three conditions must be met together: grave matter, full knowledge, and deliberate consent (CCC 1857). If any one is missing, the sin is venial. Our guides to mortal sin and venial sin explain each, and the seven deadly sins describe the roots that many sins grow from. Never conclude that another person is in mortal sin: the judgment of souls belongs to God alone (CCC 1861).

Is any sin too great for God’s mercy?

No. “The Gospel is the revelation in Jesus Christ of God’s mercy to sinners” (CCC 1846). The whole point of naming sin is that it can be forgiven: as Saint Paul writes, “where sin increased, grace abounded all the more” (CCC 1848). There is no sin so great that God’s mercy cannot reach it, for anyone who turns back.

There is one condition, and it is only honesty. “To receive his mercy, we must admit our faults” (CCC 1847). God, the Catechism says, is like a physician who uncovers the wound in order to heal it (CCC 1848). That is all an examination of sin is for: not to accuse you, but to let the light in so that grace can do its work.

What should I do about the sin I find?

Bring it to God, and bring the grave sins to Confession. The ordinary path is simple: make an honest examination of conscience, be sorry for what you find, and resolve with God’s help to change. If you want to understand that sorrow, our guide on how to repent walks through it step by step.

Then go to the sacrament. Confessing your sins to a priest is how Christ chose to reconcile us; if you are nervous or it has been a while, how to go to Confession gives you the words. Mortal sins must be confessed; venial sins need not be, though the Church strongly recommends it (CCC 1458).

Sources

Cited by paragraph and verse, so you can read them in full. In the end, your priest has the final word.

• –Catechism of the Catholic Church, 1849–1851
• –Catechism of the Catholic Church, 1852–1853
• –Catechism of the Catholic Church, 1854–1864
• –Catechism of the Catholic Church, 1846–1848
• –Catechism of the Catholic Church, 1868–1869
• –Catechism of the Catholic Church, 396–409
• –Romans 3:23; James 4:17
• –Psalm 51 (50)
• –John Paul II, Reconciliatio et Paenitentia (1984), no. 16

Confession Compass is an independent educational tool, not an official body of the Catholic Church. It never absolves sins: only a priest, in the Sacrament of Reconciliation, can absolve.