Mortal and Venial Sin
The question
Aren't all sins equal in God's eyes, so why split them into categories?
Scripture · 1 John 5:17
All wrongdoing is sin, but there is sin which is not mortal.
A short answer
It's a common idea: a lie is a lie, murder is murder, and to a perfect God they're all the same. But Scripture itself doesn't talk that way. John writes plainly that "there is sin which is mortal" and "sin which is not mortal" (1 John 5:16-17). He even tells us to pray differently depending on which we're dealing with. So the distinction isn't a Catholic invention — it's right there in the text.
Think about it the way you'd think about a relationship. There's the thoughtless thing you say that bruises a friendship, and there's the betrayal that ends it. Both are real wounds, but they're not the same wound. Mortal sin is the second kind: it's grave matter, done with full knowledge and deliberate consent, and it severs the life of grace in us (CCC 1855-1857). Venial sin damages and weakens that life without killing it. Jesus assumes degrees too — "that servant who knew his master's will... shall receive a severe beating" while the one who didn't "shall receive a light beating" (Luke 12:47-48).
The good news is that this isn't about keeping score; it's about taking love seriously. Naming the difference is how the Church helps us see when we've drifted versus when we've walked out the door — and the door is always open to come back, through confession.