Why would God damn anyone to eternity in Hell?

I willingly believe that the damned are, in one sense, successful, rebels to the end; that the doors of hell are locked on the inside.

All that are in Hell, choose it. Without that self-choice there could be no Hell. No soul that seriously and constantly desires joy will ever miss it. Those who seek find. To those who knock it is opened. And yourself, in a dark hour, may will [a grumbling] mood, embrace it. Ye can repent and come out of it again. But there may come a day when you can do that no longer. Then there will be no you left to criticize the mood…
   —excerpted from The Problem of Pain and The Great Divorce, by C.S. Lewis (1898-1963), included in The Quotable Lewis, 1989 Tyndale

In a sense, the concept of hell gives meaning to our lives. It tells us that the moral choices we make day by day have eternal significance, that our behavior has consequences lasting to eternity, that God Himself takes our choices seriously.

The doctrine of hell is not just some dusty theological holdover from the Middle Ages. It has significant social consequences. Without a conviction of ultimate justice, people's sense of moral obligation dissolves, and social bonds are broke.

Of course, these considerations are not the most important reason to believe in hell. Jesus repeatedly issued warnings that if we turn away from God in this life, we will be alienated from God eternally.

And yet, although “the wages of sin is death,” Paul also says that "the gift of God is eternal life in Christ Jesus our Lord" (Romans 6:23). While breath remains, it is never too late to turn to God in repentance, and when we ask for forgiveness, God eagerly grants it.
   —excerpted from Answers to Your Kids' Questions, by Chuck Colson, 2000 Prison Fellowship Ministries.

We may rest assured that no one will suffer in hell who could by any means have been won to Christ in this life. God leaves no stone unturned to rescue all who would respond to the convicting and wooing of the Holy Spirit.

As for the fate of [the damned] being eternal, it could not be otherwise. Death is not the cessation of existence but the continuation of the eternal being with which God lovingly endowed man—but now in painful separation from God and all else in utter darkness and loneliness.
   —excerpted from In Defense of the Faith, by Dave Hunt, 1996 Harvest House Publishers

“For God so loved the world, that He gave His only begotten Son, that whoever believes in Him should not perish, but have eternal life. For God did not send the Son into the world to judge the world, but that the world should be saved through Him. He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God. And this is the judgment, that the light is come into the world, and men loved the darkness rather than the light; for their deeds were evil.”
   —Jesus Christ, John 3:16-19 NASB