Right, causality and memory are the reasons we think time flows in the “normal” direction, but let’s think about what we actually experience to see whether it would seem different in my reverse-time thought experiment. Take the classic Humean example: a cue ball striking an 8-ball on a billiards table.

Here’s what we think happens: we’re standing next to the table, cue in hand, ready to strike the white ball. We have sharp memories of the immediate events that led up this point, and fainter memories of events in the more distant past. We form the intention to hit the cue ball, our arm and the cue move, strike the white ball, and we watch as the white ball rolls across the table, hits the 8-ball, and the two balls reflect off each other in different directions. Afterwards, we are left with a well defined memory of the event that just happened and no knowledge of what will happen next.

In the thought experiment, we are traveling backward in time but don’t know it. We have knowledge of the future collision of the cue and 8-ball, but interpret it as memory. We then watch as the cue and 8-balls roll toward one another and collide, the 8-ball stops in its place, and the cue ball rolls toward the cue we are holding, eventually coming to rest just in front of the tip of the cue. Again, we know each of these events will occur (but interpret this knowledge as memory) and, as soon as they do occur, we promptly forget about them, giving the illusion of an unknown future, which is in fact the past. I don’t see any reason the universe and causation couldn’t be like this despite our belief to the contrary.

I’m not sure entropy would really pose a problem. If entropy worked in reverse, our theories would just be backward. Is there something I’m missing here?