No, I Don't Think We Live in a Simulation

I've heard this argument many times from people I have intellectual respect for. The claim says that if a universe is able to produce a machine that simulates reality, then it's extremely likely that the world we live in is, in fact, a simulation.

Let's first recognize the huge assumption here. Why do we take for granted that it's possible to produce a realistic simulation of a universe which is non-trivial. The game The Sims is far from sufficient demonstration. I don't think this is the weakest part of the argument. There's no reason to think that unencumbered scientific and engineering progress will one day allow human beings to create machines that generate believable simulations of the universe. How far in the future that will be is unclear. Whether or not conscious beings can inhabit that simulation is another matter entirely.

Although I'm ultimately willing to concede on both those points, the burden of proof should not be overlooked.

The problem I have with such arguments is a little more fundamental. Let's assume an advanced intelligence (human or otherwise) found itself capable of creating such a simulation. That simulation must run on some sort of computer. That computer will require energy to power it. It will take up space. It will make occasional errors. It will produce heat which will weaken parts of the machine, requiring it to be repaired.

Let us assume an intelligent species dedicates itself completely to this task. The create a Dyson sphere and focus the maximum amount of energy towards the project. Let it be a bit more science fiction. Assume these simulation creators live in some wildly exotic place governed by different rules of physics. There are likely to be some fundamental truths, like the laws of thermodynamics. Maybe their universe is tuned differently, but it still has limits on how much energy can be put into the simulation.

Of if we accept the creator's universe to be so unbelievably different that they have no such restrictions, for whatever reason, they still chose to impose limitations like that on the universe they created, if we in fact, live in side a simulation.

Should we as a species one day achieve the ability to create our own simulated universe, and dedicate all our resources to the effort, our resources will be finite. Even if we found a way to conscript the majority of the matter and energy in our universe toward the task of simulation, the best we can hope to achieve is simulating a universe slightly smaller than ours. Our simulation machine would have to track the state of the simulated universe. Even if we store that state compressed and efficiently, there's still a finite amount of matter in the universe with which to build storage.

Our simulation machine might be unthinkably large, but it would only be able to simulate a slightly smaller universe. That universe, in turn, could at best, simulate something smaller than itself. At each level, the universes will be smaller and smaller, like Russian dolls.

While I can't totally rule out the possibility that I do live in a simulation, I don't think it can possibly be turtles all the way down. Arguments claiming that the possibility of a single simulation implies a high likelihood of being in a simulation are flawed in this logical leap.

Such arguments also assume that the universe is relatively easy to simulate. Are there any processes in nature which occur at a rate faster than any possible algorithm could simulate them? I'm not actually sure. I think if there was some aspect of nature that behaved in this way, clever engineers might find a way to exploit that aspect of the universe to create a new type of computer which uses nature itself to do these sorts of calculations. This, in some sense, is the core inspiration for quantum computing. There are aspects of nature that evolve in a way which cannot efficiently be simulated using a classical computer.

So perhaps a universe simulating machine would have sub-routines that perform quantum computing operations or even other more exotic types of calculations yet to be dreamed up. Thus, I can't really claim that the universe does things which can't be simulated. However, this concept does introduce some complications that the simulation argument fails to address at all.

If you believe that our universe is a simulation, then it naturally follows that you must believe conscious artificial intelligence is possible; it logically follows. Although, you can also reject the antecedent (our universe isn't a simulation) and still accept the consequent (AI is possible).

While I'm open to the possibility that simulated universes exist. Perhaps a more advanced alien civilization lives elsewhere in our universe and has created one. Maybe one day we will create one. I'm even open to the possibility that we do indeed live in a simulation. But I don't believe it follows logically from the belief that simulated universes are possible. When in discussions on this matter, a good skeptic will remind their conversation partners that the burden of proof lies with the person making the claim.