> None of this explains why your original argument does not apply to past macrostates.

Yeah, that's gonna be a long row to hoe if I can't even get you to acknowledge that there's a difference between the past and the future independent of the second law itself.

Maybe I should just ask: do you think there is any difference between the past and future (independent of the 2nd law)? If so, what is it?

But in the meantime:

> that implies you lack information on the record

This turns on what it means to have information "about" something. All of the data I have first hand access to comes to me through my senses, mainly my eyesight. When I say a coin is heads-up it's because I can see the coin, i.e. there are photons emitted from the coin (presumably) that end up on my retina and create electrical impulses that go to my brain and leave me with the subjective sensation of seeing a heads-up coin. There are all kinds of background assumptions about how light works, how coins work, how my retina works, and how my brain works, but for the most part one chooses to sweep those under the rug and accept as a working hypothesis that the reason I have the subjective sensation of seeing a heads-up coin is that there is in point of actual fact a coin "out there" and that it is, again in point of actual fact, heads-up.

But the camera is a very different story. I get direct input from the camera in the same way that I get direct input from the coin. I can see the camera just as I can see the coin. But unlike the coin, the camera's state with respect to what it has recorded is not directly apparent to me. That state is part of the internal state of the camera. It is hidden from me. I cannot directly observe it simply by looking passively at the camera the way I can with the coin while my visual cortex of my brain does the heavy lifting. I cannot even tell that there is hidden internal state based on anything that I can see about the camera while it is recording.

Making a prediction about what will happen during "playback" (indeed, even predicting that there will be something interesting to observe at all!) requires a much more complicated model of the world and chain of inference than it took for me to conclude that the coin was heads-up.

I introduced multiple cameras so that the structure of the example eliminated all that complexity and everything was symmetric. All the cameras are the same, and my knowledge of them is all the same -- until I start looking at the playback, at which point things start to diverge. When I look at the playback on one camera, I now have direct information about the (previously hidden) state of that camera, but not of any of the others.

So here again the question is: why should (direct) information about the state of one camera tell me anything about the state of any of the other cameras? It is because of a very complex chain of inference, part of which includes the hypothesis that there are, in point of actual fact, events which have occurred in the past (and which now cannot be changed) and that there are things in the present (like cameras) whose states correspond to those past events, and for that reason correlate with each other in the present.

I've lived a long time and I've engaged in a lot of philosophical discussions, but you are the first person with whom I've ever had to go into that level of detail on such a foundational matter. Not that there's anything wrong with that, you're keeping me on my toes. But my point is just that if you're going to insist that I be excruciatingly precise about something this elementary, it's going to be a very long time before we can come back to talking about thermodynamics.