Recent research has attempted to mathematically quantify the probability that we are running in a computer simulation. The arguments made are plausible, but the researcher ultimately just guesses a 20% probability based on his “gut instinct”, which is hardly scientific. Since I am a staunch nondeterminist, it would take more than this to convince me. However, let’s assume the researcher is correct for the sake of argument. For a culture to conceive of a computer powerful enough to simulate not only the structure of the universe, but also the intelligence of the “NPCs” (that is, us), it would need to be quite advanced. Since any culture that advanced must have a significant measure of intelligence, it also stands that at least some among them are themselves nondeterminists (from a simply philosophical point of view, having nothing to do with one’s understanding of physics). Thus, paradoxically, we would expect the world to be more random than it is. If the simulation in question were some sort of game, as some have postulated, I would expect that it would also be more epic (though this would very heavily depend on what is considered entertainment by whoever is doing the simulating).

Additionally, if a 20% probability exists that we are in a simulated universe, what of the one doing the simulating? Since the researchers assume nothing about the actual structure of the universe, that means that universe should also have a 20% chance of being simulated. As the number of universes approaches infinity, the probability that they are all simulated approaches 0, but the problem would become computationally intractable by even the most advanced computers long before that happened (regardless of the power of a computer that a civilization could build, each successive simulation would require a more powerful computer, as it would need to emulate the capabilities of the computers inside of the simulation). Thus the researcher’s assumption that it is highly probable that a computer powerful enough to simulate the universe exists may be flawed.

Finally, there is the question of actual theoretical intractability, which is probably my strongest counterargument. Regardless of the laws of physics, the laws of mathematics are largely independent of the universe we live in. Some of the processes within the universe are NP-complete or EXPTIME-complete, and do not lend themselves to solutions for large numbers of input even on the fastest of computers. When dealing with the scale of a universe, the numbers are immense, and the processes taking place would be simply impossible to simulate unless every atom was itself a computer. This is highly improbable in a simulation for a number of reasons, chief among them that the overhead of communicating between these systems to create a singe undivided universe would be greater than that of solving the problem in the first place and that from an engineering perspective, it would make more sense to centralize the operations of this system so it would be easier to manage and monitor.

That’s another thing – if this were a simulation, we would expect “backdoors” built into the universe. Even if we could not use these, we should expect evidence of their use by those simulating the universe. And since they’re running things, there is a chance that they’re keeping track of us, as intelligent beings (even if we’re not the subject of this simulation, which is quite possible) every so often, in which case we would expect them to have made contact already.