Causality is just human perception and there's nothing special about time. Let me try to explain this in three ways, going from intuitive/trivial to non-intuiti

Causality is just human perception and there's nothing special about time. Let me try to explain this in three ways, going from intuitive/trivial to non-intuitive/mind-blowing: • You can have causality in space rather than time: e.g. a convolutional image filter at pixel 13 might consider pixels 12, 13, 14 (of which the first two are causal and the last is non-causal, if we consider higher numbers as going "forward") • You can have non-causal filters in time: e.g. audio compression at time 0:30 might consider not only the portion of audio from 0:00 to 0:30, but also the audio from 0:30 to 2:33. (This doesn't seem that remarkable, because the track has already been recorded, so it's not in "real time".) • Finally, what we usually think of as intuitive causality in "real time" is simply a question of entropy. We think of a person dying because she was shot by a bullet, but we could also replay the movie backwards and think of all the tissues of a human body coming together in such a way as to propel the bullet backwards at a high velocity - in other words the wound causes the bullet to fly! The only reason we don't think of it this way is because the latter explanation decreases rather than increases entropy. As it turns out, physicists can show that entropy is also the exact reason why we remember the past and not the future. (And if we did remember the future and not the past, we would simply think of the future as the past and vice versa, so things wouldn't feel any different.)