## Unreality

I read an argument some years ago explaining why it is highly likely that we human beings are living in a computer simulation. It was quite elegant, and I felt compelled to share it here. It goes something like this:

If it is possible to create a simulation of a universe with sufficient complexity to eventually contain conscious observers, then  it is highly likely that other such simulations will be built in the original universe. Even if they are not, simulations will be built within the simulated universe. Then, the original universe applies recursively to each level of simulation, until a level is reached where the simulation cannot be complex enough to contain conscious observers (this is inevitable, since any simulated universe must be less complex than the universe in which it is simulated: if you assigned one bit to each particle in the universe, the simulated universe would still only be as large as the original universe itself, setting an upper bound on its size). Still, provided a single initial starting universe, the number of simulated universes will far outnumber that of real ones, so the probability is highest that we, as conscious observers, exist in such a simulation. (Think about somebody dropped into a random universe. Which universe would they most likely find themselves in?)

There are, however, a few cases where this argument does not hold.

1. If it is not possible for a universe to be simulated in a manner complex enough to allow for conscious observers to develop within it.
2. Nobody ever builds a simulation in the first place.
3. We are living in a multiverse. If there is more than one universe, then most theories hold that there will be an infinite number. Since an infinite number of simulated universes is possible in such a situation, but there is also an infinite number of universes, the maximum probability that we are living in a simulation should be (should, but I’m not great with transfinite mathematics) fifty percent.