dreams and memories

Most of us have had some kind of precognitive dream, so we know that dreams can seem to foretell the future, but can they work in reverse?

One evening, I watched a movie that had a scene featuring a bus. That night, I had a dream featuring a bus. Did I dream about the bus because I saw one in the movie? or did I see one in a movie because I would dream about a bus that night? These are the kinds of mind-bending questions that arise and show me how deeply embedded are my concepts of time and space and causality.

Throughout my life, I have believed that something that happened in the past has determined something that happens now or in the future. (This is so closely enmeshed with free will that it's difficult to talk about one without the other, but I will do my best and save more about free will for another day!) Hundreds of years ago, the philosopher David Hume alerted us to the problem with this belief. He pointed out that causality isn't something we actually see; we infer it. And the direction in which we infer it is past --> present --> future.

Let's play around with Hume's famous example of billiard balls. And while we're at it, let's make a short film. We have in front of us a billiards table with all its colorful balls. We see a cue strike a red ball. Leaving aside questions of causality, what we see is that the red ball collides with a yellow ball. The yellow ball moves. We say that the red ball struck the yellow ball, causing it to move. All good, right? Now let's play the film backwards. Now the yellow ball hits the red ball, causing it to move.

"But that isn't how things work," you may argue. How do you know that isn't how things work? It's worth asking how we know what we know, especially when it comes to knowledge about which we feel very confident.

Let's leave billiards aside and return to buses, in particular my dream bus. If we retool our concept of causality to allow it to function in more than one direction, we can ask another mind-bending question: Are dreams composed of the memories of events of the day or are they the backward predictors of those events? Or both? Or something else altogether?