When you’re asking yourself “Is this a grave matter” you’re acting about whether a material evil happened. This material evil has nothing to do with your will. It’s the part of sin that is objective. So when we say we aren’t moral relativists, we are basically saying that material evil and material goodness exists. They’re not just social constructs. Good is good and evil is evil. Evil is recognized by the negation of the good. Evil doesn’t exist in itself.
So a better analogy would be running over someone with your car. The material evil is that the person lost their life. Death is an evil because it is the loss of life. The moral component involves my willfulness. So, in one situation, it might be a dark night with icy roads. I was being reasonably attentive on the road but failed to notice the person. Then I did everything in my power to avoid hitting them. But everything happened so fast and I still didn’t avoid it. In this case, I have no moral culpability for the evil. There’s literally nothing deliberate about it. I’m aware of the evil and their death even may haunt me afterward. I may fear getting in my car afterward. I can even feel guilty and question if I really DID everything I could. But such questions would be scrupulous to ask. My will was completely aimed at a respect for life.
Now maybe I might learn something from that, but we must also be careful of being over zealous in our avoidance. We have to avoid taking more blame than is due to us.
Now say that I wasn’t being attentive. Say I was driving while intoxicated. I didn’t intend to hit them, but I put myself in a morally wreckless situation that resulted in their death. My willful actions are once removed. I didn’t intentionally kill the person but I was gravely irresponsible. This is sort of my failure to avoid a near occassion of sin. I’m to blame but through a degree of seperation. I the drinking and driving is what I need to repent of. I should recognize the death wasn’t willful, but still recognize my level of culpability for their death.
The gravest and most willful way to go about this --the mortal sin, that is, is to know that is a person in the road and to deliberately steer your car into them. Now, some might tell you that those other things are mortal sins as well because they cry out for so much justice. But usually when people say this its because they view venial sins as small matters we shouldn’t bother with. They’re the sins we can get away with.
Our goal should be to want to avoid doing evil and do what is good. Thus I’d spend less time on discerning what category of sin you’re in. If you’re sincerely striving to do good and avoid evil, you won’t fall into mortal sin, AND you will earnestly go to confession for the graces, not because you’re selfishly fearing for your own eternal wellbeing. Fearing hell will always result in doing the bare minimum which is a graver sin in itself.
