So, think about a movie, one that’s not part of a trilogy or a larger world or anything. Just a story ’bout a boy and a girl. Your standard love story. They meet, fight, fall in love, circumstances drive them apart, then through the power of love they overcome the obstacles and the story ends when they get married.
The story ends at marriage, but that does mean that their lives did. Or does it? These aren’t real people, they’re fictional characters. They might as well have gotten hit by a bus right after the credits rolled.
This problem is why epilogues get written. A short little blurb giving a little bit of insight into how the characters continue to evolve after the events of the story.
What does this have to do with eternity? Well think about your life. Death is the end of your story. But that doesn’t necessarily mean you stop existing. Just that this particular “book of you” ends, and a new one begins.
Eternity is “the unspecified number of stories that happens after the ending of a particular one.” It can also mean, “the weight of the current moment and the fact that, despite it’s perceived length, it’s also only a tiny portion of the whole story.” In the sense that “an eternity passed while you waited for your mom to pick you up after band practice.”
When you die, you go to heaven, forever. What does this ‘forever’ mean? It means, “long enough to where you won’t remember the circumstances by which you evolved in your initial story.”
It can’t mean anything else. God promised the Jews that the Davidian line of kings would last forever. He kept that promise, to those particular Jews. The line of kings lasted long enough so that the world that created the promise that God made couldn’t recognize the reason why God made that promise anymore.
Eternity means, “as long as you can remember.” After the eternity, you need a new story to base your identity around. The epilogue to your story as a human being is much less rich, far less interesting than the actual story was, otherwise we’d be telling that story and not this one. Depictions of a heroic character in the afterlife tend to be extremely short, extremely hazy, and revolve around the relationships they made in life. “And he drank ales in the great beer hall of Valhalla with his dear friends forever.” What else would he have to do? How long do you think you’d do that before you got restless for a new adventure?
Eternity is the “space in which little changes.” You define time by events, events are defined by interestingness. Long spaces of time in which nothing much of interest happens, that’s eternity.
This is why God doesn’t tell us in very specific detail what happens after we die. Thinking about it in our own terms is more interesting and contributes to our story more than the actual knowledge would.