When did the Roman Catholic idea of mortal sins develop? Also the theory of being in a “state of grace” and that mortal sins “drive out” the grace of God? I have seen many of the early Latin fathers talking about mortal sin, but I don’t see where they hold the theory of being in a state of grace (whatever that means). I have looked it up and can’t find a single thing on this “being in a state of grace” thing. When did this develop? Was it another medieval invention like purgatory and indulgences?