“Prequels are really difficult,” Alan Dean Foster once said. The main reasons I recall him giving were that usually the readers who most wanted to read a sequel were fans of the original work. Therefore, they already knew the characters’ future, removing one source of dramatic tension. Also, they often had already imagined their own version of events, and whatever the author comes up with may not match up to their expectations.

Another reason is that the author often doesn’t know exactly what happened. So when we try to put the events into some sort of narrative that is satisfying to us, it may not actually add up to an interesting story.

This will prompt some people to ask, “But it’s your story! How can you not know the details?!”

Let me give an example from one of my current writing projects. At the moment it consists of two novels: one is a sequel to the another. In the first book, one of my protagonists is an apparently human, somewhat mysterious, fortune teller. One of the villains is the Zombie Lord. One of the mysteries surrounding the fortune teller is that she has some sort of past relationship with the Zombie Lord.

For plot purposes in the first book, the readers needed to know that some sort of friendly relationship had once existed, but there had been a falling out. So I’ve included only enough information to establish that before it becomes important. And no more.

At the time I was writing the first book, I knew more than the little bit I revealed, but it wasn’t a huge amount more. I didn’t need to know more. I knew how well they know each other, and how they feel about each other now, so I could write their interaction (and eventual combat) correctly, but that’s all I needed to know, so it’s all I’d figured out.

In the second book, their past—and their relationships to several more characters—is integral to the plot. So I have figured and filled in a few more details. Again, I’m figuring out more than will actually appear in the story, but there’s a lot I’m not worrying about.

One of the things I don’t know, for instance, is exactly what sequence of events led to them ceasing to be friends. Ultimately, it was because he became an evil overlord, of course, but was there a defining moment? An action he took where it became obvious that’s the path he was going down? Or was it a gradual thing?

All creative people do that sort of thing. For example, say you have this idea for a poem or a painting or a song about what it feels like to be a young person who decides to throw all your problems and cares away and just leave, start a new life on the other side of the country or something. So you create the work of art, and you do everything in your power to capture that feeling, and you might end up with something like this:

After writing it you spend the next forty years being asked by reporters, fans, and talk show hosts what exactly was the crime that set this whole thing off. For all of those forty years you keep coming up with variants on the answer that you don’t know, it didn’t matter for you in creating the piece. What was important was that feeling you were trying to evoke. He wanted his listeners to project themselves into the song and just experience that moment.

The other reason it doesn’t matter is because part of the point of art is to engage the audience. That song isn’t only about what Paul Simon was thinking when he wrote it. The song is also about what each and every listener who hears it finds within it. My meaning, when I hear it and sing along, is just as viable and true as the meaning he had when he wrote it. Your meaning when you hear it is just as viable and true, as well. His meaning when he performs it all these years later is no more, and no less, true than the meaning that someone who his never heard it before may find if they hear a recording tomorrow.

We leave things unsaid in stories because we should only include things that move the story along. We leave them unsaid because in our pursuit of telling the best version of the story we can, we can’t afford to let ourselves run down rabbit holes and lose the story. We leave them unsaid because the story isn’t real until it is heard or read and believed by an audience. We leave them unsaid because the audience can’t throw them self into the story unless we leave room for them.