“Philosophers took this idea from the physicists and came up with their own theory,” Dr. Brier continued. “They called it the Many Minds. Their theory is that all these endless choices, all these parallel lives, really do exist—not in the big wide universe, but inside our individual brains. We’re the ones who divide like amoebas over and over. Still sound crazy? Well, think about your dreams. A dream is an elaborate world that your brain creates instantaneously. All that extraordinary detail devoted to building a fantasy place that only exists for a few moments of sleep, never to be visited again. If the brain can do that night after night after night, then maybe it isn’t so strange to think that it can build entire parallel worlds, too. No, for me, the important question isn’t whether it’s possible. The question is, What does this have to do with you and me and our actual lives? With our single little branch of the tree? Does any of this really matter if it’s all just theoretical? Because physicists and philosophers don’t agree on much, but they do agree on one thing. Whether it’s Many Worlds or Many Minds, we’re stuck on our own branch. Isolated. Powerless. Every version of yourself lives in its own separate world, and you can’t visit those other universes.”

Dr. Brier let all of that sink in. She took a sip of water from a bottle on the stool placed in the middle of the stage. Before she began to speak, I saw it again. Her eyes shifted to the balcony.

She stared directly at me.

“Or can you?”

After her speech was over, I waited in a long line to meet her. This whole event was about selling books. She’d written a self-help book, using the hook of the Many Worlds, Many Minds theories to give it a sexy twist. The idea was to teach people to lead better lives by showing them how to “visit” the alternate choices they’d made in parallel worlds.

Still wondering if you should have asked your college girlfriend to marry you? Imagine the version of yourself that’s living in that world.

Trying to decide whether to take that new job? Somewhere in the universe, you will. What does that life look like?

I understood the appeal of the theory. I was drawn to the idea that there was a universe right now where I hadn’t driven into that river. Somewhere, either in another world or buried inside my head, Karly was still alive, and I was still with her.

Believe me, I would have done anything to have that life for myself.

But that was a different Dylan. A Dylan who made better choices.