The Simulation Argument, formulated by Nick Bostrom, aims to show that you’re probably inside a simulated world. It assumes that enough civilizations like ours go on to spawn posthuman descendants that create many such worlds, and that enough of those worlds are like Earth. In all of spacetime, simulated versions of our civilization then outnumber originals. (Note that the Simulation Argument is not the same thing as the conclusion that you’re in a simulation.)

I think the argument and assumptions could hold up. If so, what does that mean we should do? Robin Hanson has made some suggestions. It seems to me, though, that (to a first approximation) the possibility of being in a simulation should make no difference to the behavior of a non-egoist agent. Here’s a quick informal argument.

Imagine you’re in a huge tree. It’s foggy, so you can’t tell whether you’re at the trunk or at one of a subset of the tree’s (sub-)branches. There are many branches and only one trunk, so you can assume you’re probably at a branch. You feel a strange urge to apply chemicals to the wood, and have two choices. One chemical, BranchKiller, is deadly to branches but not the main trunk; the other chemical, TrunkKiller, is deadly to the main trunk but not the branches. Assume you like the tree and want to save as much of it as possible.

In this situation, you should clearly apply BranchKiller, not TrunkKiller. Since you’re probably at a branch, it’s true that BranchKiller is more likely to harm the tree. But if you are at the trunk, the effects will spread to all branches. If you had some clones, one at each trunk or branch you think you might find yourself, then using TrunkKiller would always kill the entire tree, and using BranchKiller would always kill only part of the tree.

Now imagine the tree is the universe, the trunk is base-level reality, and the branches are simulated worlds. It’s possible that people in simulated worlds could do things to affect their fate that wouldn’t work in base-level reality. But for every decision made in a simulated world, base-level reality trumps that decision. We in base-level reality get to decide (if only very indirectly) what universes, if any, are created, and whether they can be influenced post-creation. Making sacrifices in base-level reality for gain in simulated worlds is like killing the tree’s trunk to save its branches. Unless we can very reliably help simulated worlds at very little cost in base-level reality, it seems to me we can just ignore the simulation issue entirely.

Update: see the comments for some corrections and clarifications.