Q. Would missing Mass on a Sunday only be a mortal sin if you knew the teaching? Do we sin at all if we don’t know that it is a sin?
A. The Catechism tells us that three conditions – that it is grave, that we must know what we are doing, and that we consent to it – are the key to determining how culpable someone is for their sin. If one condition is missing, the sin would be venial. But missing Mass is always a grave matter – whether you know it is or not. However, if the understanding that it is a grave matter (as you suggest) or consent is missing, it may not be a mortal sin. So the person, for example, who was told it is okay to miss Mass would be lacking in their understanding. If someone knew it was wrong not to go but was prevented by – let’s say a spouse – from going, then full consent would be missing. If a person knows all three conditions and they choose otherwise, they have fallen into mortal sin. Whether it is venial or mortal, charity is still being hurt. Even if people ignorantly skip Mass, they are still missing out on the graces received, and this harms one’s love for God.
Perhaps ignorance is saving a lot of people from mortal sin, but we cannot see that as being bliss. They are still being put in bondage by sin, and it is harming them even if they do not realize it. We are not immune to its effects, even if we are ignorant of how much it is hurting us. Thus we do need to trust Jesus that the truth will set us free. It will shock them at first, but with His grace, truth will bring them to the glorious freedom of the children of God!