What we see and what there is are two kind of different things. Whatever it says is basically this idea of a wave function, a quantum mechanical way of describing these superpositions of all the possibilities. It's not just a convenient tool for making predictions, it's real. What individual observers observe is just what we see. They see that they're in an individual universe where measurement outcomes are definite but elsewhere in the wave function, there are all these other universes where we see different things. So it's a challenge to completely change your idea about what reality is and how it works. All comes out of a set of equations that were based on fitting experimental data.