Scripture and the Catholic Church make clear distinctions between two different kinds of sin based on the gravity of sin: mortal sin and venial sin.
First, let’s define “sin.” Sin is an offense against God. It damages or breaks our relationship with him.
Put simply: sin separates and grace unites.
The extent to which that relationship is effected by sin is how we make the distinction between mortal sin and venial sin.
When we are in a state of grace, we are united with God in charity and love. Our will aligns with his will. But, when we turn away from God, we commit sin and that affects our relationship with him.
A venial sin hurts our relationship with God, but allows charity to remain even though it is wounded.
A mortal sin, on the other hand, destroys charity in our hearts. We are separated from God.
What makes a sin a mortal sin? Three things:
- Grave Matter – It is a serious act. It breaks the Ten Commandments for example.
- Full Knowledge – You know that it is wrong.
- Complete Consent – Freely choose to do it.
So how do you repair that relationship with Christ? How do you restore charity?
Grace. Grace is the free and undeserved gift of God of his life. We get grace in a special way through the sacraments. When you are in a state of mortal sin, separated from God, you can restore that relationship and seek God’s mercy and forgiveness in the Sacrament of Reconciliation (and Baptism of course).
When your relationship with God is hurt by venial sin, the grace we experience in the Eucharist as well as the other sacraments, especially Baptism and Reconciliation can repair that relationship. Grace is also given through prayer and the study of Scripture and the living out of special charisms from God and whatever other means we use to unite ourselves with the Lord.
Because ultimately this is about a relationship. Grace unites us with God, our hope and our salvation. Sin separates us from God.