Will unbelievers continue to be unbelievers at the end of the age?

It seems a stretch to me to imagine that people might retain any kind of unbelief after seeing God the Father on judgment day. Consider Saul/Paul on the road to Damascus; this was a man entirely devoted to the destruction of Christianity, a Pharisee of Pharisees, a group whom Jesus had condemned as being remarkably hardened, perverters of the law of God. One vision and Paul did a complete 180, becoming the author of a huge chunk of the New Testament.

I myself am an annihilationist, so the question of how long this belief might persist is moot, but I do not believe it would so easily fade. And of course it will be too little, too late, to prevent their judgment. James 2:19, ESV: "You believe that God is one; you do well. Even the demons believe—and shudder!"

I am going to answer the question from the Christian Inclusivism perspective.

As you clarified in your comment about the meaning of "unbelievers":

... in the sense that there is no intellectual acknowledgement of Jesus being Lord. At some point, like the demons in James 2:19, there will be intellectual acknowledgement

and you clarified the meaning of "continue" in your question as follows:

But how long that will last, I don't know. If "conditional" universalism is true, than I suppose the intellectual sting of facing the reality of God, with a short time of weeping and gnashing of teeth, will be like facing a time of purgatory on the way to a universal restoration.

my answer would be NO and YES depending on the 2 meanings of "believe" in the English language (see my answer on a related question about James 2:19):

• NO, they cannot remain unbelievers because when they stand before God there is no longer epistemic uncertainty. They will be confronted with the stark reality of God's existence, the Lord Jesus's right to judge, and the full awareness of their own heart where

  • God will assist their memory by "replaying" all their acts over their lifetime (evident in many reports of near death experience)
  • By now, the clouding of their conscience caused by their fallen reason/desire has disappeared, and they are now confronted with the full clarify of their conscience which by now has become judge of their own acts according to God's law

• YES, they will remain unbelievers IF during their lifetime they have either A) sufficiently understood the gospel but rejected explicitly; B) did not know the gospel but have rejected it implicitly by rejecting God the Creator as

  1. the source of moral standard: they create their own "right" and "wrong" and/or refuse to be judged as sinners
  2. the revealer of humanity's brokenness: they refuse to see Scripture and conscience as mirror which shows how the "power of sin" clearly ruling their life in the form of both rebellion and concupiscence / weakness
  3. the provider of redemption: they refuse to accept God's offer of 1) forgiveness and 2) grace to heal their brokenness, evidenced by how they refuse to forgive those who trespass against them
  4. the lover of humanity: they refuse to receive and to house the Holy Spirit's gift of new life in their heart, evidenced by how they have not loved others as themselves

In contrast, believers who by then also have been given the same epistemic certainty, will now be joyful as they recognize in the face of Lord Jesus something that they have longed for and loved during their lifetime, mediated by their imperfect knowledge of the gospel or by the Holy Spirit ministry in their hearts. C.S. Lewis tried to capture this moment in the 7th book of the Chronicles of Narnia The Last Battle chapter 14:

The creatures came rushing on, their eyes brighter and brighter as they drew nearer and nearer to the standing Stars. But as they came right up to Aslan one or other of two things happened to each of them. They all looked straight in his face; I don't think they had any choice about that. And when some looked, the expression of their faces changed terribly — it was fear and hatred: except that, on the faces of Talking Beasts, the fear and hatred lasted only for a fraction of a second. You could see that they suddenly ceased to be Talking Beasts. They were just ordinary animals. And all the creatures who looked at Aslan in that way swerved to their right, his left, and disappeared into his huge black shadow, which (as you have heard) streamed away to the left of the doorway. The children never saw them again. I don't know what became of them. But the others looked in the face of Aslan and loved him, though some of them were very frightened at the same time. And all these came in at the Door, in on Aslan's right. There were some queer specimens among them. Eustace even recognised one of those very Dwarfs who had helped to shoot the Horses. But he had no time to wonder about that sort of thing (and anyway it was no business of his) for a great joy put everything else out of his head. Among the happy creatures who now came crowding round Tirian and his friends were all those whom they had thought dead. There was Roonwit the Centaur and Jewel the Unicorn, and the good Boar and the good Bear and Farsight the Eagle, and the dear Dogs and the Horses, and Poggin the Dwarf.

The Bible states that by the very end, everyone will "know" and be forced to acknowledge the existence of God. But that doesn't mean they will be willing to accept it. The scriptures say that the last days will climax with God's government exercising and regaining complete control over mankind. Most humans will refuse to acknowledge this transition of power and will forcefully resist it. This will trigger Armageddon.

As the author of the answer being quoted, I suppose it's only fair that I expand.

(Disclaimers: I am not a universalist. I am a fence-sitter on annihilationism.)

There's a difference between what someone does "in the heat of the moment", when confronted frontally with God's reality, and their thought process when that reality is no longer imminent. In fact, the Bible very strongly suggests (and I believe) that all people know, on some level, that God exists. Because of our sinful nature, however, we really, really want to deny that existence. Some are exceptionally good at such denial.

Since "hell" is eternal separation from God, I see no reason why such people would not, as you (and Lewis) put it, continue to rationalize away their rejection of God.

In other words, when God's fullness is put in front of your face, "every knee" will bow. Some out of respect and, one can suppose, gratitude. Some out of terror and/or confusion. Those latter, once no longer in God's presence, will — I suspect (and Lewis seems to agree) — again be free to return to their denial.

At the same time, they'll know, on some level, what they've known all along, but they'll be lying to themselves, just as they are now.

That all said, I also believe this is only natural, and to be expected. As fallible humans, we can't entirely trust our senses, or know with certainty that anything is true. I expect that having restored bodies and being in the presence of God will remove these fallibilities in a way that we can be truly certain that they are gone. Whether the unrighteous will be granted the same, I don't know, and ultimately the answer hinges about this.