So what needs to be explained is why our capacities are structured so as to carve up phase space in a manner that leads to the Second Law. But this is partly a question about us, and it’s the sort of question that invites an answer based on an observation selection effect—something like “Agency is only possible if the system’s capacities are structured so as to carve up its environment in this manner.” My view is that the asymmetry of the Second Law is a consequence of an asymmetry in agency—the temporal direction in which agents can form and read reliable records about a system’s state must differ from the temporal direction in which an agent’s action can alter a system’s state.
Interesting idea, but doesn’t it lead to something akin to the Boltzmann Brain problem? This asymmetry would hold for an agent’s brain and its close environment, but I don’t see a reason why it should hold in the same way for the wider universe. So shouldn’t we predict that when we make new observations with information coming from outside our previous past lightcone, we will not see the same Second Law holding? Or maybe I have misunderstood you completely...
The Boltzmann brain problem usually arises when your model assigns a probability distribution over the universal phase space according to which an arbitrary observer is more likely to be a Boltzmann brain than an ordinary observer. There are various reasons why my model does not succumb to this probabilistic kind of Boltzmann brain problem which I’d be happy to go into if you desire.
However, your particular concern seems to be of a different kind. It’s not that Boltzmann brains are more likely according to the model, it is that the model gives no reason to suppose that we are not Boltzmann brains. The model does not tell us why we should expect macroscopic regularities to continue to hold outside our immediate environment. Is this an accurate assessment of your worry? If it is, I think it is demanding too much of a physical model. You are essentially asking for a solution to the problem of induction, I think. My view is that we should expect (certain) macroscopic regularities to persist for the same sorts of reasons that we expect microscopic regularities to persist. Of course, if there were specific probabilistic arguments against the persistence of macroscopic regularities, I would have a problem. But like I said above, those don’t arise for my model the same way they do for Boltzmann’s.
Yes, your second paragraph gets at what I was thinking (and you are right that it is not exactly the Boltzmann Brain problem). But I don’t think it is the same as the general problem of induction, either.
On your model, if I understand correctly, there are microscopic, time symmetric laws that hold everywhere. (That they hold everywhere and not just on our experience we take for granted—we are not allowing Humean worries about induction while doing physics, and that’s fine.) But on top of that, there is a macroscopic law that we observe, the Second Law, and you are proposing (I think—maybe I misunderstand you) that its explanation lies in that we are agents and observers, and that the immediate environment of a system that is an agent and observer must exhibit this kind of time asymmetry. But then, we should not expect this macroscopic regularity to hold beyond our immediate environment. I think this is ordinary scientific reasoning, not Humean skepticism.
Do you have a similar concern about Tegmark’s anthropic argument for the microscopic laws? It only establishes that we must be in a universe where our immediate environment follows those laws, not that those laws hold everywhere in the universe.
Interesting idea, but doesn’t it lead to something akin to the Boltzmann Brain problem? This asymmetry would hold for an agent’s brain and its close environment, but I don’t see a reason why it should hold in the same way for the wider universe. So shouldn’t we predict that when we make new observations with information coming from outside our previous past lightcone, we will not see the same Second Law holding? Or maybe I have misunderstood you completely...
The Boltzmann brain problem usually arises when your model assigns a probability distribution over the universal phase space according to which an arbitrary observer is more likely to be a Boltzmann brain than an ordinary observer. There are various reasons why my model does not succumb to this probabilistic kind of Boltzmann brain problem which I’d be happy to go into if you desire.
However, your particular concern seems to be of a different kind. It’s not that Boltzmann brains are more likely according to the model, it is that the model gives no reason to suppose that we are not Boltzmann brains. The model does not tell us why we should expect macroscopic regularities to continue to hold outside our immediate environment. Is this an accurate assessment of your worry? If it is, I think it is demanding too much of a physical model. You are essentially asking for a solution to the problem of induction, I think. My view is that we should expect (certain) macroscopic regularities to persist for the same sorts of reasons that we expect microscopic regularities to persist. Of course, if there were specific probabilistic arguments against the persistence of macroscopic regularities, I would have a problem. But like I said above, those don’t arise for my model the same way they do for Boltzmann’s.
Yes, your second paragraph gets at what I was thinking (and you are right that it is not exactly the Boltzmann Brain problem). But I don’t think it is the same as the general problem of induction, either.
On your model, if I understand correctly, there are microscopic, time symmetric laws that hold everywhere. (That they hold everywhere and not just on our experience we take for granted—we are not allowing Humean worries about induction while doing physics, and that’s fine.) But on top of that, there is a macroscopic law that we observe, the Second Law, and you are proposing (I think—maybe I misunderstand you) that its explanation lies in that we are agents and observers, and that the immediate environment of a system that is an agent and observer must exhibit this kind of time asymmetry. But then, we should not expect this macroscopic regularity to hold beyond our immediate environment. I think this is ordinary scientific reasoning, not Humean skepticism.
Do you have a similar concern about Tegmark’s anthropic argument for the microscopic laws? It only establishes that we must be in a universe where our immediate environment follows those laws, not that those laws hold everywhere in the universe.
I am not really familiar with the details of Tegmark’s proposal. If your two-sentece summary is accurate, then yes, I would have concerns.
Hmmm… I’m not yet sure how bothered I should be about your worry. Possibly a lot. I’ll have to think about it.