An objective mortal sin is a knowingly chosen act of the human person, an act which is objectively gravely immoral. An actual mortal sin is an objective mortal sin which is committed with full knowledge of its grave immorality and full deliberation (full freedom of choice).
Suppose that an act is objectively only a venial sin, or objectively not a sin at all. If a person mistakenly thinks that the act is gravely immoral, and commits that act with full knowledge and full deliberation, the act is an actual mortal sin. For it is always gravely immoral to freely and knowingly choose to do what you yourself think to be gravely immoral.
In this fallen sinful world, many persons commit objective mortal sins without full knowledge of the gravely immoral of the act. Their choice is an objective mortal sin, but not an actual mortal sin.
Only actual mortal sin deprives the soul of the state of grace. Only unrepented actual mortal sin deserves eternal punishment in Hell.
Therefore, persons who are unrepentant from objective mortal sins, which are not also actual mortal sins, can be saved even if, unfortunately, they do not realize their error and give up those sins prior to death. As long as the individual entered the state of grace by some form of baptism, and either never committed an actual mortal sin or at least repented from all actual mortal sins, that person will die in the state of grace and have eternal life.
This implies that atheists can be saved without converting to belief in God. Their refusal to believe in God might not be an actual mortal sin, and therefore they might be saved. They can enter the state of grace by an implicit baptism of desire and return to the state of grace after any actual mortal sin by an act of implicit perfect contrition. Some atheists may be guilty to the extent of actual mortal sin for their rejection of God and religion; other atheists might be in a state of invincible ignorance.
The same can be said about other sins. Homosexuals who are sexually active or in a legal same-sex marriage can possibly be saved without giving up this sinful behavior — if they are invincibly ignorant of the gravely immoral of their actions and not guilty (or at least repentant) from other types of grave sin. The state of grace can be possessed by persons who unfortunately do not realize that their actions are gravely immoral. This includes various sexual sins, the divorced and remarried, cohabitating couples, and other sins. Some persons might be guilty to the extent of actual mortal sin for their sexual sins; others might be in a state of invincible ignorance.
However, there are limits to invincible ignorance. Some grave sins are so severe that they cannot be mistaken by a sincere conscience for morally permissible acts. In all cases, God is the judge over each person and their conscience.
by
Ronald L. Conte Jr.
Roman Catholic theologian and translator of the Catholic Public Domain Version of the Bible.
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the reproach of Christ 
Hi Ron,
Another very interesting and well written post. I’m interested in your thoughts on the following in relation age and knowingly committing mortal sin. in a book I read lately, “Hungry Souls” by Gerard J.M. van den Aardweg, he makes reference to documented cases of suffering souls in Purgatory at ages as young as 7. He also talks about I believe Amelia, a teenage friend of the sisters of Fatima. When they asked the Blessed Virgin, was she in Heaven, she responded that Amelia would be in purgatory till the end of the world.
I find it real scary that a child as young as 7 and even a teenager could be suffering in Purgatory. I believe we don’t reach an age of reason until much later.
I would love to hear your thoughts on this.
The sufferings of Purgatory are just and merciful. So persons there suffer only as much as they deserve — no! they suffer less than they deserve, due to the mercy of God and the prayers of the faithful for the souls in Purgatory. So the sufferings of a child who has reached the age of reason (not necessarily 7) in Purgatory, would be quite limited.
I think the friend in of the Fatima visionary was about 18 or 19 (IIRC), so she was an adult. Also, the length of time in Purgatory does not tell us the degree of suffering during that time. The girl may have had some (perhaps many) hidden grave sins, which fell short of actual mortal sin.
Another consideration is that time in Purgatory is not the same as time on earth. So the expression of being in Purgatory until the general Resurrection is not as bad as it might seem. Mary was using the example of that girl to teach us that some souls are in Purgatory for a long time, and that some souls go to the general Resurrection directly from Purgatory, not only from Heaven and Hell.
hmmm no way to edit errata in comments post posting — (1) the stray word “to” needs removal after “the 7 Sacraments” — (2) insufficient MATTER (pls change “are used” to “is used”)
Well stated above. However, some of the other topics seem to have 1 or 2 comments and no way to enter a comment so I’m commenting here that I think that too many Catholics simply do not understand and have not been taught / have not studied or learned the simple fact that Christ Himself defined and instituted the MATTER & FORM required for each of the 7 Sacraments to. Valid MATTER is crucial to each Sacrament and the non-topic of “women’s Ordination” becomes as clear as the fact that there is no Baptism if invalid / insufficient MATTER such as milk or coke or rose petals are used instead of WATER. A woman is not, cannot be, and will never be a man; milk or coke or rose petals will never be water — so any Bishop “ordaining” a woman can do so until he drops because it is simply impossible to ordain a woman just as a child is NOT baptized if mike, coke or rose petals are used instead of water; etc.
See my post: Are Women Valid Matter for Ordination? The valid matter for ordination is the imposition of hands. The Magisterium has NEVER taught that women are not valid matter for ordination, nor that a baptized male is the valid matter for ordination.