People of all times, places and religions have instinctively known that there will be a final judgment and reward or punishment after death. This knowledge is built right into us.
Heaven and hell are logical extensions of God's character:
• God is HOLY. He has established good and consistent physical and spiritual laws we can depend upon.
• God is JUST. There is penalty for wrong choices. Hell (total separation from God after death) is the penalty for a lifetime of sin.
• God is LOVE. He offers a substitute (Jesus) to free us from the penalty. If we accept, we get heaven instead of hell.
The substitution is a gift, and hell is what's left if the gift is rejected.