You seem to be saying that all sin is mortal.
No. That is not what I am saying at all…If you follow the thread, the question by the OP was “would committing a
deliberate venial sin on a Sunday be more serious or grave than usual?”
The operative word is not “Sunday” but “deliberate”.
Deliberate makes the otherwise venial sin mortal. It may not be the gravity of the venial sin, but by taking it upon oneself to say it is venial and not mortal is at odds with the First Commandment, where
we are saying we are wise enough to skirt the intend of the Law by only focusing on the letter of the law.
Venial sin may only damage our relationship with God (where mortal sin breaks the relationship),
deliberate damaging this sacred relationship is extremely grave!
This makes a
deliberate venial sin, whether on Sunday or any day, grave matter, and by virtue of being deliberate it indicates both full knowledge, and willful consent…and therefore the actual sin is both grave matter, but meets the litmus test for mortal sin.
What is left out of the conversation is the mercy of God, where if we acknowledge the sin, confess it, are contrite, and do penance, we are absolved of our human frailty.
This should be our focus.
Pax et Bonum!