Q. According to the Baltimore Catechism, not attending Mass is a mortal sin. What is it that makes it a mortal sin?
A. It is also a mortal sin in the present Catechism and from the day God gave the law to Moses to observe the Sabbath! This idea didn’t diminish as time went on. On the contrary, from the days of the early Christians, the Sabbath corresponded with a celebration of the Eucharist – to honour this day as the victory of the Cross and Resurrection. That is why Sunday is holy – so that we can partake of this great mystery, our salvation in Christ where we are fed with His very Self. I am afraid any other way we observe the Sabbath is going to fall very short of so awesome a divine reality!
The obligation to make Sunday a day of rest is not as rigid as it was in Jesus’ time when they would do no work at all. Dishes do have to be washed after a big dinner after all! But we are called to avoid unnecessary work that would make Sunday into a workday. In our modern culture, where stores and services operate 7 days a week, this can sometimes be difficult. But the Church still gives us many opportunities to attend Mass by offering a variety of Mass times – no excuses there…
What makes skipping Mass a mortal sin is that we place something else in our lives as more important than the worship of God, which is idolatry. We make some man-made activity more important than worshiping God and being nourished by Him. Certainly missing Mass due to illness, a sick child, a cancelled flight that prevents us from making Mass – where we want to go but cannot – is certainly not a sin. If we skip because we would rather sleep in, go skiing, or go to a movie, for example – when that becomes our priority over Mass – we choose ourselves and other things over Him. As our Creator and Savior that is just petty. Is one or two hours a week really asking too much? Plus, I have found that when people say they will worship God in their own way on the Sabbath while on the ski hill or at the mall, they do not likely do so. When I snowboard, I may think of God as I am looking over a cliff that I do not want to fall off of, but I am not spending the day praying and worshiping Him. Plus we are not connected to a larger faith community, and that is a big part of it as well. We should worship God as communal beings before all else on Sunday.