What does it mean for the universe to be a simulation?

Question

Amongst philosophers in general... what exactly is meant by the universe or reality itself being a simulation?

Simulation is fairly clear to me, when works "within" the assumptions of the framework of our physical world... ie: simulations like video games, VR games... these things are entities within our "normal" world. The existence of these things isn't puzzling.

What does it mean to say the universe is a simulation vs the universe is not a simulation? Are we talking about the existence of a controller/god... like the evil genius God Descartes was referring to or Berkeley's god? I don't think it's this, because atheists are also making these simulation claims.

What distinguishes a non-simulated reality from a simulated one (in meaning)?

EDIT: As an example maybe... what does Nick Bostrom mean exactly by "simulation" in his simulation hypothesis? What is he arguing for?

Answer 1

Speaking as a computer engineer, having another "human" civilization "simulate" ours seems highly implausible. The computer power to simulate one human brain would require one of the largest computers in existence, and this computer would run on the order of 1000 times slower than the brain, and require on the order of 15 megawatts to operate. I'm not able to find hard numbers on physical size, but some clues I've found suggest that the physical size of this would be around 1000 cubic meters.

So to simulate the brains of 7.6 billion people on earth would consume over 100 billion megawatts of power, while the earth's electrical power production is on the order of 2 million megawatts. And the computer would occupy 7 trillion cubic meters, whereas the volume of earth is around 1 trillion.

Of course advances in technology would reduce these numbers, but, given the currently-known limits of physics, probably by not much more than about a factor of 10. And remember that the simulation would still be incredibly slow (though, again, it might speed up by a factor of 10).

So clearly the simulation of earth and its population by another earth-sized civilization is beyond impractical. Of course a larger civilization on a larger planet might attempt it, but it still would only be simulating earth's brains, not any of the environment, and not the rest of the universe as known to human brains. (Though partially simulating the rest of the universe does introduce some interesting parallels to "known" physics principles such as those surrounding quantum mechanics).

(Note: Some of my back-of-the-envelope computations above may be wrong, but likely not dramatically, in terms of the implications.)

Answer 2

You might wish to read the discussion here Are we living in a simulation? The evidence

I quote from my answer there:

"David Chalmers has argued that we should consider the 'simulation hypothesis' not as a skeptical hypothesis that threatens our having knowledge of the external world but as a metaphysical hypothesis regarding what our world is actually made of. " http://philosophycommons.typepad.com/flickers_of_freedom/2014/08/the-case-for-libertarian-compatibilism-a-brief-overview.html

Although we are nowhere near creating fully realistic simulations, and probably don't even know how far we are off, it does seem it's inevitable in our future. Just like we cannot transfer minds, yet, but we will, has profound implications for identity, so simulation does for understanding what 'real' means.

I would describe simulstion-thinking as an iteration of the same sceptical thinking of Zhuangzhi's question whether he 'dreamed he was a butterfly or whether he was a butterfly now dreaming he was a man', Buddha's analysis of samsara, & Descartes scepticism. But, with the frisson of our expanding understanding of our future/s.

Answer 3

The simulation argument can't be referring to Descartes's cunning deceiver, for the reason Descartes points out. Even if everything I perceive, everything I experience, is an illusion created by the great computer in the sky, my "I", my subjective consciousness, exists and is separate from the deception. Simulation theory is incomplete. Perhaps my couch and my laptop and my room are an illusion; but the "I" that experiences these illusions is not. It's separate from the deceiver, separate from the deceptions. And what is my "I"? It's outside the simulation. So Cartesian simulation doesn't explain all of reality. It leaves the deepest mystery, the "I", unsolved.

So simulation theory must be saying that it's my "I" itself, my very consciousness, the thing (whatever it is) that experiences my experience, that is also being simulated. And there, Bostrom's argument fails. The premise is that 40 years ago we had crude video games like Pong, and today we have hyper-realistic video games, and in the future they'll be indistinguishable from reality. I have no doubt that's true.

But Bostrom does not explain how consciousness itself will be implemented by a computer. We have no idea how to do that, nor any theory that says it's even possible. Turing machines are extremely constrained. They do one discrete thing at a time and can't solve the Halting problem. That's an example of a problem that we can conceive that no computer can solve. There's no evidence, only a belief on the part of some, that the universe is so constrained. Some people think Turing machines can be conscious, but nobody knows how.

Bostrom's premise fails. In the future we'll have super-duper realistic experiences to enjoy. But there's no evidence or even a convincing argument that subjective consciousness can be implemented. The argument is just wrong. And it's a bit disingenuous, because it begins with the Pong versus modern video games analogy, but sneakily ignores the problem of subjective experience. Descartes did not miss that point. He noted that even if the great computer in the sky is programming my reality, it can't program my subjective experience. I exist separately from the simulation.

Bostrom's analogy from Pong to modern video games is false. The electronic paddles in Pong did not have subjective consciousness; nor do the avatars in modern video games. In terms of the core mystery of subjective experience, no progress at all has been made in the past 40 years. And that destroys Bostrom's premise.

Please see my other response to this question here, which makes similar points.