There are a few who say that hell is not eternal and that some day God’s mercy will overcome his justice and hell will be emptied. What does the Bible and catechism say about this?
CCC 1021 Death puts an end to human life as the time open to either accepting or rejecting the divine grace manifested in Christ.
CCC 393 It is the irrevocable character of their choice, and not a defect in the infinite divine mercy, that makes the angels’ sin unforgivable. "There is no repentance for the angels after their fall, just as there is no repentance for men after death." [St. John Damascene, Defide orth. 2, 4: PG 94, 877]
So the catechism is clear that once we have died we have made our choice. And it is in fact a choice that we make here on earth.
The Bible says in Hebrews 9:27 And just as it is appointed for men to die once, and after that comes judgment
So we have had our chance and then comes judgment…now something that we must keep in mind is that God is not a jerk. Everyone is offered the grace to go to heaven. Now to some it might not be as evident as it is to others but that is God’s business. Just because Jimmy down the street saw an apparition of our Lady and you didn’t doesn’t mean that he is guaranteed a place in heaven. He still needs to obey the gospel the best way he knows.
There is also in Romans 2:14-16 When Gentiles who have not the law do by nature what the law requires, they are a law to themselves, even though they do not have the law. 15 They show that what the law requires is written on their hearts, while their conscience also bears witness and their conflicting thoughts accuse or perhaps excuse them 16 on that day when, according to my gospel, God judges the secrets of men by Christ Jesus.
Exactly so keep those things in mind
Continuing on, Jesus says in Matthew 25:41 that Hell was originally prepared for the devil and his angels.
It wasn’t originally created for humans who had rebelled but for the angels. But now we see that those who share in the sin of disobedience before death share in the fate of the devils and are sent to Hell.
But is Hell eternal! Yes and to those who did not clothe, feed, or visit Christ he will say - Matthew 25:46 And they will go away into eternal punishment, but the righteous into eternal life."
Notice that there is a contrast between the eternity of the punishment and the eternity of the reward.
If someone argues that God’s mercy will some day triumph over his justice and thus free the souls from hell, how do we know that at some later date God’s justice won’t triumph over his mercy and send everyone to hell? This is an undependable position.
Mark 9:43-48 And if your hand causes you to sin, cut it off; it is better for you to enter life maimed than with two hands to go to hell, to the unquenchable fire. 44 45 And if your foot causes you to sin, cut it off; it is better for you to enter life lame than with two feet to be thrown into hell. 46 47 And if your eye causes you to sin, pluck it out; it is better for you to enter the kingdom of God with one eye than with two eyes to be thrown into hell, 48 where their worm does not die, and the fire is not quenched.
Now Jesus here isn’t recommending a lot of one armed one legged Christians. He is here warning us of the seriousness of this life and its effects on the afterlife. And that somehow he must communicate the terribleness of Hell, Jesus says that it is better to loose a limb than experience the pains of hell.
I would also say that there are some moral and theological danger to the teaching that hell will be emptied.
First is that in the churches 2000 years it has never taught this. So to teach it is to divorce yourself from the churches teaching.
Second I would then wonder what the purpose of purgatory would be - would a person who went to hell still have to go to purgatory?
Third, if I am going to heaven anyway, why not live it up here on earth? Its not like I am going to hell for eternity?
Finally, those who are in hell, have no wish to be in heaven because the one that they refused to serve is there and to see him face to face for all eternity would be worse than hell.
C.S. Lewis said that the door to hell is locked - from the inside. They want to keep God out.