I am confused on what Mortal Sin means and why some things are considered mortal sins while others are not. Now before I go any further, I want to be clear that I am not looking for any loopholes or work-around; I am ONLY looking for some form of consistency. That’s all I want: consistency.
I read the catechism, but it didn’t help.
Basically, I would like a rule of thumb for what makes something grave matter? Why is it that, while all other violations of the ten commandment fall under a spectrum with lots of room between mortal and non-mortal.
Here’s what I mean illustrated by some examples:
Deceit is a sin, lying to a courtroom to get someone wrongly convicted of a capitol offense is a mortal sin, and lying about your favorite sports team to avoid an argument is only a venial sin.
Meanwhile lust is a sin, cheating on your spouse with a prostitute while away on a business trip is a mortal sin, but so is having sex with your spouse in a non-procreative way.
This feels problematic for two reasons.
The first, as previously mentioned, is that there is no scale. An unrepentant masturbater and an unrepentant serial rapist get the same punishment when they die, despite one being many magnitudes worse than the other.
The second problem is that the rule of thumb I usually use to gauge gravity can’t be applied. For other sins it is easy to point out who is being hurt and how badly he/she is being hurt. Murder is a mortal sin because the victim is deprived of life, grand theft is a mortal sin because the victim is deprived of resources that might be irrecoverable, but who is being hurt in masturbation and in non-procreative marital intercourse? When explaining why these are grave matters nobody ever points to anyone being hurt, instead they say “it is intrinsically evil because God forbade it because it is intrinsically evil because …”.
So can anyone explain how I am misunderstanding the catechism and/or why it isn’t inconsistent for ALL non-natural sex to be grave matters when not all acts of violence and/or theft share that distinction?