David Clotfelter spends the first third of Sinners in the Hands of a Good God: Reconciling Divine Judgment and Mercy on the subject of hell—establishing what the Bible says about it, responding to alternate interpretations, and discussing the justice of never-ending punishment for our sin.
Regarding the justice issue, Clotfelter offers the explanation given by Anselm and Jonathan Edwards:
[B]ecause God is a Being of infinite worth, to whom we owe an infinite obligation, sin against God is an infinite evil requiring an infinite punishment. And since the punishments of hell cannot be infinite in intensity, as that would violate the principle that the lost are punished according to their deeds, it must be the case that hell is infinite in duration.
As he explains, the fact that our sins require an infinite punishment makes it necessary for Jesus to pay for those sins. A crime against an infinitely worthy being requires a punishment that a finite person will never finish paying; a punishment paid by an infinitely worthy being pays for that crime.
But sometimes the question comes up of how those who have been forgiven by God will view hell throughout eternity. Will they be saddened forever by its continued existence? Here’s what Clotfelter has to say:
[I]f indeed it is just for God to punish the wicked everlastingly, then it is a certainty that the saints in heaven will perceive that justice and will rejoice in its administration, even as they rejoice in all of God’s works and decisions. This does not mean that either they or God will derive glee from watching the torments of the damned. It means that they will agree that God’s decision to punish the wicked is right and good, and that the punishment that He allots to each lost person is precisely what that person deserves. They will realize that it is only God’s grace that stands between them and a similar fate, and so there will be no element of pride or vindictiveness in their joy….
[T]he joy the redeemed in heaven will feel over the punishment of the wicked will in no way derive from sadism or a spirit of revenge, but it will express their gratitude toward God for their own salvation and their clear-eyed understanding of the justice of His judgments.
As fallen creatures, we greatly overestimate our righteousness and vastly underestimate God’s. So when the doctrine of hell first brings us face-to-face with the truth about both, we naturally rebel against it emotionally. The temptation is to exchange the Bible’s words about hell for something—like universalism (everyone will be saved) or annihilationism (the lost will cease to exist)—that makes more immediate sense to us. But don’t give up when you find yourself in tension with the Bible. Instead, dig until you find all the pieces you need to see the complete picture that honors and glorifies the true God.
God is not merely holy; He is infinitely holy. He is not merely good; He is so good as to pay an infinite price for our salvation. He does not merely dislike sin; He hates it with a passion that can be fully expressed only on Calvary or in the depths of an everlasting hell. The Bible’s doctrine of eternal punishment does not only teach us about punishment; it teaches us about the character of God. As John Piper has written, “The infinite horrors of hell are intended by God to be a vivid demonstration of the infinite value of the glory of God.”