Is it a mortal sin to miss Mass on a Sunday without a good reason, simply because you don't bother, or is it a matter of individual conscience?
Since questions about mortal sin frequently frighten people or give rise to complaints about the dark old days and fear of hell, let us first be clear that a mortal sin is only committed when the matter is serious in itself, when the person has full knowledge that it is seriously sinful, and when full consent of the will is given to the action. Some people take this to mean that hardly anyone ever commits a mortal sin, but the Church's practice suggests a more robust view of our human nature and our ability to commit sin.
If we commit a mortal sin, we may not receive Holy Communion until we have made a sacramental confession. This does not mean that we are condemned to hell until we have been to confession. An act of contrition, made out of the love of God will restore us to grace there and then, as indeed the "penny catechism" teaches, if we also have the intention of receiving the sacrament of penance in due course.
The answer to your question is that the Church teaches that missing Mass on days of precept through our own fault is grievous matter. If we know this and there is no excusing cause then we have committed a mortal sin. Our conscience is not a matter of deciding for ourselves what is right or wrong; our conscience speaks within us to warn us away from sin and to prompt us to good. It is our duty to inform our conscience according to the teaching of the Church so that it points us towards the truth. Our properly informed conscience should ideally help us not simply to avoid sin and do the minimum, but to act in the way most pleasing to God, especially in valuing the privilege of participating in the most holy Eucharist in which Christ's redeeming sacrifice on the cross is offered for us.
Catholic Dilemmas column published in the Catholic Herald
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