Sandro Botticelli (1445–1510), ‘Chart of Hell’ (created after Dante's ‘Divine Comedy’
Life without God in eternity is a dreadful, horrific thing called hell.
An atheist said to a Christian in online debate: “If hell is as painful as Christians believe it to be, then the time will certainly come when the souls there will think they have had enough and repent and go back to God.”
This rests on several fallacies:
1. Concerning what it truly means to have a free will.
In Christian terms, to be truly free is to follow God and to become more and more holy by His grace, because that is our purpose: why we were created, and therefore what makes us the most happy and fulfilled. Human beings, however, do not have a free will apart from this grace of God, because they are in rebellion against God (the Christian doctrine of the fall and original sin).
Now, rather than always desire to follow God and achieve freedom to be what we were intended to be, we have a strong tendency to sin and rebellion against God. The grace is available to all, yet some reject it. The ones who reject this grace and the God Who freely gives it, in love, are simply not free. They are in an abnormal, fallen state.
Therefore, souls in hell no longer even have the capacity to freely choose God, since that very choice is made possible only by God's grace, which is no longer available in hell, by definition, because hell is existence without God at all, by the choice of the persons who end up there.
2. The denial that there can be a profoundly, utterly obstinate will, even if “free” and the myth that a “free” will would always, naturally choose to follow God (that being a far better and more rational choice than hellfire and eternal punishment).
This is closely related to #1. Setting aside the important question of whether a rebellious will is truly free or not, we can also argue that there is such a thing as a will so stubborn and rebellious that it has essentially created its own demise, in terms of no longer being able to change and repent while in a damned reprobate state, in hell. C. S. Lewis made a very famous statement that “the doors of hell are locked on the inside.” The person in hell wanted to live separate from God. That was his or her choice.
Now, granted, they didn't fully think through what hell entailed. This was part of the devil's deception and game that he plays, so that people will reject God and actually think that the alternative: life without God, is preferable; even far better than life with God.
We see this mentality in off-the-cuff remarks of “great parties in hell” or “the saints are boring and no fun at all” or the infantile mindset that we find in, for example, atheist Billy Joel's song, Only the Good Die Young.
This life is a period of grace for all men. God makes the choice to follow Him freely available to all (universal atonement, over against the heretical and unbiblical limited atonement of Calvinism). We don't yet truly know what life without God is actually like. That remains to be seen and experienced in hell.
In any event, God simply lets those who wish to reject Him do so. It has consequences; people are warned about it in the Bible and in sermons and homilies. They know enough to know that it is undesirable to go to hell. So what grounds do they have to want to get out of it, having achieved their wish?
That is simply how reality works: life without God in eternity is a dreadful, horrific thing called hell. The guy who wrote these objections has been fully warned about hell, because he writes about how he disagrees with the doctrine. So he knows about it, but rejects it and God. So he may end up there himself (if he willfully rejects God and the gospel with full awareness that it is true), but if so, he won't have any grounds in reason or justice to be allowed out of it.
3. The notion that the punishment in hell somehow becomes unjust simply because persons there figure out that they messed up in rejecting God in the first place, therefore ending up in torment, and that God ought to “change His mind” and let them out.
This is a fallacy because it presupposes that God's mercy and forgiveness must necessarily last forever. But why should that be the case? On what reasonable or moral grounds? If indeed, God has freely provided mercy and grace and the ability to be saved and go to heaven, during our entire lifetimes on earth, why would He be obliged to do so forever?
Why must we assume that this isn't sufficient or that it doesn't allow adequate recourse or access to the knowledge of what it takes to avoid hell and attain eternal life in heaven (entirely by grace, but requiring also our assent)?
In fact, there is no basis to this objection at all. It may falsely assume that people end up in hell due to ignorance and no particular fault of their own (which might conceivably apply as a critique of supralapsarian Calvinism) and deny original sin and the rebellion of the human race, but the biblical and Catholic and Orthodox and non-Calvinist Protestant teaching is that sinner freely reject God after having been given ample opportunity to repent and follow Him.
So why must God give them another chance, when they have had a lifetime of chances already? Irrevocable reality intervenes at some point. In this instance it is called hell: life without God: with no love or grace or good or true or righteous.
Nor does it follow that God doesn't desire the salvation of all because (in the end) some reject that salvation. God merely leaves them to their desires. This is arguably the utmost honoring of man's dignity and free will, on God's part.