In a recent SE post on epistemic certainty about the truth claims of Christianity a helpful response was given:
Is there any way for a rational person to reach the conclusion that Christianity is definitely true?
Yes. Die and stand before God.
Snark aside, I'd be shocked if there aren't people that would doubt even then. It is human nature (and the action of the Adversary) that we have doubts. We aren't 100% certain that gravity is "true", despite overwhelming evidence. Thomas was an apostle and he had doubts. Even after the invitation to touch the risen Lord, I'd be surprised if he didn't sometimes have the thought that perhaps he hallucinated the whole thing.
His answer is not that unlike what C. S. Lewis gave in his essay “Miracles.” Lewis writes:
Whatever experiences we may have, we shall not regard them as miraculous if we already hold a a philosophy which excludes the supernatural… If the end of the world appeared in all the literal trappings of the Apocalypse, if the modern materialist saw with his own eyes the heavens rolled up and the great white throne appearing, if had the sensation of being hurled into the Lake of Fire, he would continue forever, in that lake itself, to regard his experience as an illusion and to find the explanation of it in psycho-analysis, or cerebral pathology.
It is intriguing to think that unbelievers will remain unbelievers, even after judgment day. At the end of the age, perhaps God will let unbelievers be comfortable in their own materialist illusions of living a life where He does not exist. Being given heavenly bodies that quickly become corrupted by sin, the non redeemed might very well slowly fade away from the reality of God and heaven into eternal decay - i.e. the Lake of Fire. See Lewis' Great Divorce.
However, Romans 14:11 states
... every knee will bow before me; every tongue will acknowledge God.
Is it possible that there will be some sort of momentary grasp by unbelievers of the reality of God, that appears at judgement day, including the weeping and gnashing of teeth against Him? If so, might this acknowledgment of God quickly fade away like the Pharaoh's hardening of heart in unbelief during the days of Moses? What are some Christian thoughts about this idea?