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Any reasoning you do about the simulation hypothesis has one gigantic problem - the only thing you know anything about is the universe we observe. You have neve

Any reasoning you do about the simulation hypothesis has one gigantic problem - the only thing you know anything about is the universe we observe. You have never seen a real universe and you have never seen a simulated universe, so you have nothing to compare our universe against in order to decide whether ours is real or simulated. Imagine we have a really close look at space and discover that it is made out of small voxels. Simulated universe! No! Who said that real universes are not made out of small voxels? It could be the other way around, the real universe could be made out of voxels but a voxel-based simulation does not fit into memory, so they assigned a real position vector to every object in order to approximate the real voxel universe. In that case it would be wrong to conclude that our universe is real because it is continuous and a flawed analogy with our own computer simulations suggests that simulations must be discretized in some way. [1] So no matter what you observe in our universe, you have no idea if it is indicative of a real or simulated universe. Maybe if the stars in the Milky Way would suddenly rearrange themselves and spell out »You are in a simulation.« on the night sky, that could be a good hint that we are indeed in a simulation. But even then, maybe that is just how real universes behave, spelling out messages on the night sky from time to time might just be part of the laws of physics. Admittedly, if that actually ever happened, I would also consider the simulation hypothesis the better explanation. [1] This is just an illustrative example, whether this is realistic or even possible is besides the point.

vidarh 3y ago
As I said, it proves nothing, and I just made the same argument that we can't really know because we're stuck inside in another comment. So let me violently agree with your comment. The best we could hope for would be someone popping their metaphorical head in and telling us there's an outside and then show us, but that just gives rise to the question of whether that "outer universe" is simulated or not, so infinite regress here we come. Ultimately we just have to accept that we can never conclusively prove whether we're in the "outermost layer", and we can only prove we're not if we somehow "escape" and can look in on our own universe from the outside and for what we know we're in an unexploitable simulation, so the lack of evidence of either certainly does not prove the other and we're left wildly speculating and it's not very useful. But that doesn't make the mechanisms less interesting to explore, and for me it's mostly a series of fun thought experiments, and your voxel example to me is a good illustration of what an interesting rabbit hole it is even if it doesn't lead to anything practical. For me it was an interesting one because the simulation argument is really a rehashed variant of Berkeley's philosophical idealism, and the same conflict with materialism exists for the simulation argument as with respect to Berkeley: We can speculate about it, but since we can't prove it, day to day we need to act on the assumption we live in a material world. If someone pops their head in to inform us we're in a simulation, then sure, then we can reasses. Until then it's an entertaining diversion. EDIT: I'll add one caveat, though: You're right in as much as talking about what we can say about a simulation by looking at our universe, but the core of the original simulation argument is much more pared back. It's an argument that if we can run simulations and eventually do, then statistically we are more likely to be in a simulation. Or to pare it back further: If there are 3 or more "realities" and 2 of them are simulation, then we are more likely to be in one of the simulated ones than the single "real" world. What that boils down to, then, is how realistic you think it is that someone will simulate this time period, and we can assert some limited things about that if we get to the point of running our own realistic simulations. But until/unless we get there, we can't really assess the odds, and even if we can show that such simulations are common, you're of course still right that it won't prove whether we are in one or not.
- danbruc 3y ago
  Yes, the recent popularity stems from Bostrom's simulation argument trilemma. But everyone always jumps over that, takes it as granted that we live in a simulation, and proposes some wild ideas how we could find evidence or what might be hints of the simulation. This is what I wanted to address, that this is a relatively hopeless endeavour and I do have the impression that most people talking about living in a simulation are not aware of this. Despite, as you point out, it being a variation of solipsism about which people have pondered for centuries. To address the actual trilemma, I think the solution is that there are or will be no simulations. Generally the most compact representation of a thing is the thing itself. If you want to simulate something faithfully, then the simulator will need more resources than what you simulate. You are not going to build an electron simulator that needs less than one electron to simulate one electron. You are not going to simulate a computer with a gigabyte of memory on a computer with a gigabyte of memory. That might work under special conditions, when the simulated memory is mostly zeros and you can compress it, but it will not work in general. You can simulate the weather on earth well enough for the whether forecast to be useful if you throw away enough details, but you are not going to simulate it in full detail with a computer much smaller than earth's atmosphere. Simulating a cubic meter of universe faithfully will generally require at least a cubic meter of computer. I do not see us building galaxy-size computers. The other option would be to go the way of the weather forecast, make the simulation as simple as possible, simulate entire humans but not cells or atoms to make the problem tractable. That seems much more plausible. In both cases it seems unlikely to me that you could deeply nest simulations. If you have a faithful simulation and simulating a cubic meter of universe requires two cubic meters of computer, then you could at best simulate a universe half the size of the real universe if you turned the entire universe into a computer. The people in that simulated universe could at best build a simulation half the size of their universe and so on. The simulated volume would exponentially approach zero with increasing nesting level. If you go the other way, if you simulate entire humans and not cells or atoms, then it is not even clear how the simulated people would go about creating their own simulator as simulating arbitrary machines is not part of the simulation. So you are forced to move towards a more faithful simulation mechanism if you want to enable nested simulations which, as said, will probably shrink the simulation volume rather quickly.

vidarh 3y ago

As I said, it proves nothing, and I just made the same argument that we can't really know because we're stuck inside in another comment. So let me violently agree with your comment. The best we could hope for would be someone popping their metaphorical head in and telling us there's an outside and then show us, but that just gives rise to the question of whether that "outer universe" is simulated or not, so infinite regress here we come. Ultimately we just have to accept that we can never conclusively prove whether we're in the "outermost layer", and we can only prove we're not if we somehow "escape" and can look in on our own universe from the outside and for what we know we're in an unexploitable simulation, so the lack of evidence of either certainly does not prove the other and we're left wildly speculating and it's not very useful. But that doesn't make the mechanisms less interesting to explore, and for me it's mostly a series of fun thought experiments, and your voxel example to me is a good illustration of what an interesting rabbit hole it is even if it doesn't lead to anything practical. For me it was an interesting one because the simulation argument is really a rehashed variant of Berkeley's philosophical idealism, and the same conflict with materialism exists for the simulation argument as with respect to Berkeley: We can speculate about it, but since we can't prove it, day to day we need to act on the assumption we live in a material world. If someone pops their head in to inform us we're in a simulation, then sure, then we can reasses. Until then it's an entertaining diversion. EDIT: I'll add one caveat, though: You're right in as much as talking about what we can say about a simulation by looking at our universe, but the core of the original simulation argument is much more pared back. It's an argument that if we can run simulations and eventually do, then statistically we are more likely to be in a simulation. Or to pare it back further: If there are 3 or more "realities" and 2 of them are simulation, then we are more likely to be in one of the simulated ones than the single "real" world. What that boils down to, then, is how realistic you think it is that someone will simulate this time period, and we can assert some limited things about that if we get to the point of running our own realistic simulations. But until/unless we get there, we can't really assess the odds, and even if we can show that such simulations are common, you're of course still right that it won't prove whether we are in one or not.

danbruc 3y ago
Yes, the recent popularity stems from Bostrom's simulation argument trilemma. But everyone always jumps over that, takes it as granted that we live in a simulation, and proposes some wild ideas how we could find evidence or what might be hints of the simulation. This is what I wanted to address, that this is a relatively hopeless endeavour and I do have the impression that most people talking about living in a simulation are not aware of this. Despite, as you point out, it being a variation of solipsism about which people have pondered for centuries. To address the actual trilemma, I think the solution is that there are or will be no simulations. Generally the most compact representation of a thing is the thing itself. If you want to simulate something faithfully, then the simulator will need more resources than what you simulate. You are not going to build an electron simulator that needs less than one electron to simulate one electron. You are not going to simulate a computer with a gigabyte of memory on a computer with a gigabyte of memory. That might work under special conditions, when the simulated memory is mostly zeros and you can compress it, but it will not work in general. You can simulate the weather on earth well enough for the whether forecast to be useful if you throw away enough details, but you are not going to simulate it in full detail with a computer much smaller than earth's atmosphere. Simulating a cubic meter of universe faithfully will generally require at least a cubic meter of computer. I do not see us building galaxy-size computers. The other option would be to go the way of the weather forecast, make the simulation as simple as possible, simulate entire humans but not cells or atoms to make the problem tractable. That seems much more plausible. In both cases it seems unlikely to me that you could deeply nest simulations. If you have a faithful simulation and simulating a cubic meter of universe requires two cubic meters of computer, then you could at best simulate a universe half the size of the real universe if you turned the entire universe into a computer. The people in that simulated universe could at best build a simulation half the size of their universe and so on. The simulated volume would exponentially approach zero with increasing nesting level. If you go the other way, if you simulate entire humans and not cells or atoms, then it is not even clear how the simulated people would go about creating their own simulator as simulating arbitrary machines is not part of the simulation. So you are forced to move towards a more faithful simulation mechanism if you want to enable nested simulations which, as said, will probably shrink the simulation volume rather quickly.