Are we living in a simulation?

This paper got some attention and amusement when it came out a few years ago:

Constraints on the Universe as a Numerical Simulation

Observable consequences of the hypothesis that the observed universe is a numerical simulation performed on a cubic space-time lattice or grid are explored. The simulation scenario is first motivated by extrapolating current trends in computational resource requirements for lattice QCD into the future. Using the historical development of lattice gauge theory technology as a guide, we assume that our universe is an early numerical simulation with unimproved Wilson fermion discretization and investigate potentially-observable consequences. Among the observables that are considered are the muon g − 2 and the current differences between determinations of α, but the most stringent bound on the inverse lattice spacing of the universe, b−1>∼ 1011 GeV, is derived from the high-energy cut off of the cosmic ray spectrum. The numerical simulation scenario could reveal itself in the distributions of the highest energy cosmic rays exhibiting a degree of rotational symmetry breaking that reflects the structure of the underlying lattice.

A friend brought up this question in a Facebook thread recently. Here’s my response.

OK here’s the thing. If the function of the simulation is to simulate physics, for whatever reason, and our awareness is epiphenomenal to that goal, then it would make sense to run it as a finite-element simulation like the cubic grid posited in that paper. However, on the other hand, if you ask the question “what would be the most efficient way to simulate what I seem to be experiencing” the answer is undoubtedly to have a neural-net-based simulation generating your own consciousness and feeding it stimuli based on an attention-driven sparse simulation of only the relevant parts of the rest of the universe. In that structure of simulation, there’s no reason at all why you would see any artifacts in the outside world because the outside world is generated only to an awareness-centric spec.

It’s also possible that it could be a hybrid, with a global universe buffer simulation used to provide an optimized sparse consistency across different minds’ awarenesses.

In any case, you run into the same problem philosophy has run into for all of time, which is that YOU don’t actually have any proof that the rest of us aren’t NPCs. The simulation has to generate a lot of information for you to feel like you are you, but it only has to generate an insignificantly small fraction of that amount of information for you to perceive me, so it wouldn’t really seem to be efficient to simulate me at the same level of richness as it’s simulating you, merely for the purpose of filtering out 99.9999999% of all that and feeding you the tiny remainder.

The standard response to that is “yeah, but it’s unlikely that you’re so special, so don’t fall into the trap of solipsism”. But that doesn’t actually make sense. You ARE absolutely that special; precisely because you have overwhelming, direct evidence for the presence of your own mental processes, and barely any evidence at all for the presence of anyone else’s mental processes. The part of the simulation that is YOU is special because it’s far and away, no contest whatsoever, the densest part of the simulation. You can argue with me all you want, but it’s prima facie that you’re experiencing you more than you’re experiencing me, so any objection you might make is pretty hollow.

Of course I’m writing this based on what I’m experiencing, but if you’re not an NPC and you’re reading this, then it applies equally well to you. And there’s no reason you should believe there’s a fully simulated consciousness here (me) if the only thing you’re experiencing is just yet another wanky out-there philosophical internet blog blather. So I’m not going to flatter my(potentially-NPC)self by claiming to be real.

Enjoy the ride