Can you disprove the universe is a computer simulation anymore than you can disprove that the world you think you see is just an illusion put into your mind by a demon, as famously mused by the philosopher RenĂŠ Descartes in his Meditations?
In theory, the beings who run the simulation could make whatever they want happen, including change the results of scientific experiments, change the outputs of computers used for mathematics, change the brains of everyone who tries to think about certain mathematical proofs in order to trick them into believing something false, and so on. If you imagine that God or a demon might be tricking you, there is no empirical result and no mathematical or logical result that can prove youâre not being tricked.
But of course the question is why we might think the universe is a computer simulation in the first place. No version of the simulation argument or simulation hypothesis has ever made sense. These are two of the objections I think are the most powerful:
There is no logically valid inference to be made about the world outside the simulation from the world inside the simulation. Thatâs just a logical non-sequitur. The world outside the simulation could be made of pudding for all we know, or it could be made of magic, or it could be run by Zeus. Maybe the simulation is run by a pipe-smoking rabbit and the âcomputerâ is actually a carrot. Why should we be able to say the world outside is any particular way because of the way the world inside is? And if we canât say that, how can we infer thereâs a world outside, or a simulation, at all?
There are obvious ethical concerns around simulating universes. Itâs not at all obvious that, if the advancement of science and technology continued indefinitely, we would eventually simulate a universe like our current universe. I think we would probably outlaw doing such a thing. If you run the simulation and can change it as you like, arenât you responsible for everything that happens in the simulation, especially the things that happen as a result of nature (e.g., infectious disease, natural disasters), and wouldnât that make you the worst murderer of all time?
While checking the Wikipedia page for the simulation hypothesis just now, I noticed the physicist Sean Carroll has a really smart reply to the simulation argument as well:
Of course one is welcome to poke holes in any of the steps of this argument. But letâs for the moment imagine that we accept them. And letâs add the observation that the hierarchy of simulations eventually bottoms out, at a set of sims that donât themselves have the ability to perform effective simulations. Given the above logic, including the idea that civilizations that have the ability to construct simulations usually construct many of them, we inevitably conclude:
We probably live in the lowest-level simulation, the one without an ability to perform effective simulations. Thatâs where the vast majority of observers are to be found.
Hopefully the conundrum is clear. The argument started with the premise that it wasnât that hard to imagine simulating a civilization â but the conclusion is that we shouldnât be able to do that at all. This is a contradiction, therefore one of the premises must be false.
This isnât such an unusual outcome in these quasi-anthropic âwe are typical observersâ kinds of arguments. The measure on all such observers often gets concentrated on some particular subset of the distribution, which might not look like we look at all. In multiverse cosmology this shows up as the âyoungness paradox.â
You could say that maybe the top-level universe is such that it can support infinite computation, so thereâs never a point when the nested hierarchy of simulations bottoms out. But, in this case, youâd be showing the logic of the first objection I brought up â if we can just stipulate anything we want about the top-level universe, then maybe the top-level universe is a sentient chocolate milkshake, and our universe is just a fleeting dream in its mind.
Can you disprove the universe is a computer simulation anymore than you can disprove that the world you think you see is just an illusion put into your mind by a demon, as famously mused by the philosopher RenĂŠ Descartes in his Meditations?
In theory, the beings who run the simulation could make whatever they want happen, including change the results of scientific experiments, change the outputs of computers used for mathematics, change the brains of everyone who tries to think about certain mathematical proofs in order to trick them into believing something false, and so on. If you imagine that God or a demon might be tricking you, there is no empirical result and no mathematical or logical result that can prove youâre not being tricked.
But of course the question is why we might think the universe is a computer simulation in the first place. No version of the simulation argument or simulation hypothesis has ever made sense. These are two of the objections I think are the most powerful:
There is no logically valid inference to be made about the world outside the simulation from the world inside the simulation. Thatâs just a logical non-sequitur. The world outside the simulation could be made of pudding for all we know, or it could be made of magic, or it could be run by Zeus. Maybe the simulation is run by a pipe-smoking rabbit and the âcomputerâ is actually a carrot. Why should we be able to say the world outside is any particular way because of the way the world inside is? And if we canât say that, how can we infer thereâs a world outside, or a simulation, at all?
There are obvious ethical concerns around simulating universes. Itâs not at all obvious that, if the advancement of science and technology continued indefinitely, we would eventually simulate a universe like our current universe. I think we would probably outlaw doing such a thing. If you run the simulation and can change it as you like, arenât you responsible for everything that happens in the simulation, especially the things that happen as a result of nature (e.g., infectious disease, natural disasters), and wouldnât that make you the worst murderer of all time?
While checking the Wikipedia page for the simulation hypothesis just now, I noticed the physicist Sean Carroll has a really smart reply to the simulation argument as well:
You could say that maybe the top-level universe is such that it can support infinite computation, so thereâs never a point when the nested hierarchy of simulations bottoms out. But, in this case, youâd be showing the logic of the first objection I brought up â if we can just stipulate anything we want about the top-level universe, then maybe the top-level universe is a sentient chocolate milkshake, and our universe is just a fleeting dream in its mind.