You know the one assumption that is never really questioned when things like this come up?
That we exist in a single reality, be it a cosmos, a simulation, or whatever.
Any context that contains a representation of your current mental state, in any form, contains a version of you indistinguishable–to yourself–from any other. That which makes no difference is no difference, so all these multiple ‘instances’ of you are in fact just you, singular.
You don’t exist in just one reality, but them all.
