Here’s a common question in salvation theology. The Church teaches, correctly and truly, that a person who dies unrepentant from even a single actual mortal sin will have eternal punishment in Hell. Why should the punishment for a single actual mortal sin be eternal? That seems unfair.
The WRONG answer goes something like this: One sin offends an infinite God infinitely, therefore the punishment is infinite.
That answer is wrong for a few reasons. One is that God is unchanging infinite Love, so He is only offended in a figurative sense. God does not change in response to our sins. Another reason is that finite creatures do not deserve infinite punishment. So even though the punishments of Hell are never-ending, they are not infinite in any other sense. Each person receives the punishment which is proportional to their sins, nothing more.
The RIGHT Answer is more complex, and takes longer to explain. But that is often the case with truth. Errors generally spread because they are simple and easy to explain. The truth about God and salvation can be complicated.
There are two types of grace: habitual grace (also called the state of grace) and actual grace. Actual grace allows and assists us in doing good. Habitual grace allows us and makes us to be good. Actual grace concerns what we do. Habitual grace concerns what we are. If you have habitual grace (the state of sanctifying grace), then you are good. We are not GOOD in the sense that God is GOOD — infinite perfect goodness by His very nature. But we are, in a very real sense, good. And since habitual grace includes the indwelling of the Most Holy Trinity, is makes sense that persons with habitual grace are good persons.
A person who is in a state of unrepented actual mortal sin can still cooperate, to some extent, with actual graces, to do good acts. Persons who repent from actual mortal sin often cooperate with actual graces, partially and haltingly, until they are ready for a full repentance that brings them back to the state of grace. But as long as a person is in a state of unrepented actual mortal sin, they are not good persons; they are, in a very real sense, evil persons.
Yes, our human nature remains good. But persons in a state of unrepented actual mortal sin are still evil persons. Their good human nature stands as a witness against them. So an act which meets all the conditions for an actual mortal sin is not merely a single offense against God. It is an act which makes the person evil. By choosing that act, the person chooses to become evil, chooses to abandon the love of God and neighbor, chooses to become the type of person who has, at least implicitly, rejected God and goodness.
So the reason that a single actual mortal sin can deserve eternal punishment is that, by such an act, and by the continued subsequent refusal to repent, the human person chooses to be evil. Hell is a place for persons who have made the choice to reject the love of God and neighbor — for all actual mortal sin is a rejection of that love. Hell is a fitting place for such persons. They have chosen to become evil, so they go to the place where evil dwells, where love is absent, where the suffering that is the natural result of rejecting goodness is visited upon them, in accord with their free choices in life.
Hell is a place where persons are punished, not only for act that were evil, but for choosing to become evil persons.
By contrast, Heaven is a place of love, where persons who have chosen to be loving, to love God and neighbor, and to live a life of love (and of repentance from all that is contrary to love). The journey to Heaven is like the destination: love. Everyone who loves their neighbor, truly and selflessly, goes to Heaven. Everyone who is unrepentant from even a single actual mortal sin is unable to love truly and selflessly, as they lack the virtues of love, faith, and hope, which make that type of love possible.
Hell is like a prison. And the fallen angels sent there are not torturers, nor guards, nor wardens. They are fellow prisoners along with reprobate human souls. Human persons in Hell suffer because of the companionship of devils, just as human persons in Heaven have joy and gladness because of the company of holy Angels. But the devils in Hell are not in charge, nor are they tasked by God with inflicting suffering directly on human souls (nor on human bodies after the general resurrection). The devils in Hell cause suffering indirectly, as it is terrible to have them as fellow prisoners.
Hell is a prison created by God and run by the power of God. The sufferings there are only as much as each person deserves, according to the justice and mercy of God: justice and mercy, not justice alone. For the Divine Nature is so thoroughly One that in that Nature justice and mercy are identical.
One of the most terrible and yet most just punishments of Hell is the act of God’s prevenient grace which prevents all the devils and souls in Hell from ever sinning again in the least. They are in a state of the rejection of God. They are in the state of blasphemy against the Holy Spirit (as it is to the Spirit that we account the conversion of sinners). But they are literally unable to sin in any way. For it would not be just for God to permit billions of persons in Hell to sin gravely innumerable times forever and ever.
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