But at that point, isn’t that no different than just saying the universe isn’t a simulation? If there is a base universe than that is the “actual” universe, and who cares about all the simulations beyond what we would care about a simulation we created? For this to be the case, I feel like there would need to be some additional features or complexities about this base universe that can’t be simulated and thus that allows those in it to prove that they are not a simulation. The issue the simulation universes have is that if they could create a simulation of their own universe they are immediately confronted with the conundrum that they themselves are probably not the first one to do this. But this theoretical base universe would have some characteristic about it that precluded them from this issue. Or maybe they don’t, maybe they think they’re simulation too but they’re not and have no way to prove otherwise, they just happen to be the base. However, if that is the case, then you can make that same argument for this universe can’t you?