I just don’t see what the mechanics are in Catholic theology for someone to unknowingly commit a mortal sin, or for someone without mortal sin to be damned. That’s my point. I get that someone with original sin alone would go to limbo, but the baptized kid doesn’t even have original sin.
We cannot say a person who unknowingly commits a mortal sin did not sin for the simple reason that a sin was indeed committed. We will never know in this life how often we are guilty of rejecting divine promptings which would have led us toward grace and away from sin, toward the faith and the truth, even into the Church for those outside of the Church. We won't know how often we did this till the next world when we will see it clearly.
Speaking of those outside of the Church, rather than working against, their free will works in conjunction with their inclination toward evil (which we all have due to Original Sin) whenever they reject the opportunity to gain grace. It may be a perceived inconvenience, selfishness, laziness, weakness or some other reason they choose for not corresponding to divine promptings, but they do, and do so always of their own free will. This rejection is commonly taught to be ignorance or invincible ignorance and is so taught in order to reward salvation to those outside of the Church.
What StanlyN said earlier is true, after the age of reason, a Catholic can only be in a state of grace or mortal sin. A Non-Catholic can only be in a state of mortal sin, if it were possible that he had never committed a mortal sin, then he must be guilty of the sin of unbelief as long as he remains outside of the Church, as taught in
Unam Sanctam: "
We believe in her firmly and we confess with simplicity that outside of her there is neither salvation nor the remission of sins..."