What is sin?

A sin is "a word, an act, or a desire contrary to the Eternal Law" (CCCC no. 392) or God's will. It is the breaking or damaging of our relationships with God, neighbor, world, and self that constitute sin (McBrien). There are various levels or degrees of sin:

1. One commits a mortal sin when there are simultaneously present: grave matter (it's serious), full knowledge (you know what you're doing), and deliberate consent (you want to do it). A mortal sin is something that destroys, breaks, or reverses our fundamental option for God. This is an act that fully engages the person and the person not only chooses the act (categorical element), but they also choose the kind of person they will become in and through the act (transcendent element); e.g., I choose to kill another person (that's serious), I know that I'm going to kill another person (full knowledge), I want to kill the other person (consent), and I'm perfectly happy becoming a murderer.

2. One commits a venial sin when the matter involved is: less serious, or even if it is grave, when full knowledge or complete consent are absent. A venial sin does not break our relationship with God. There may be a genuine decision to perform that act, but there is no decision to become that sort of person. "In a venial sin a person chooses to do a particular deed, but he or she also wants even more deeply to be the kind of person who stands opposed to the deed. There’s an element of contradiction between the act and the person doing the act" (McBrien). The person may or may not be fully engaged in the act; e.g., I walk into a candy store with my nephew and he steals a jolly rancher (not that serious).

3. A serious sin falls somewhere between a mortal sin and a venial sin. It is more inconsistent with the Gospel message than a venial sin; however, it differs from a mortal sin because we are not fully engaged and happy with the person we are becoming by doing the action or deed. An example of a serious sin would be missing mass on a Sunday for no particular reason: missing mass is serious matter and you have knowledge and consent of the act, but maybe deep down inside you do not want to be the type of person that misses mass and you regret not going afterwards.