It depends entirely on what "you" means here. In a dream, the whole reality is you, and this is not something you have to take on faith: through lucid dreaming

It depends entirely on what "you" means here. In a dream, the whole reality is you, and this is not something you have to take on faith: through lucid dreaming (or rather, its various extensions in dream yoga) it's possible to gain introspective access to all the details of the psyche that manifests as the apparent reality. That psyche doesn't belong to the dream character you thought you were but is still "you" in the most intimate sense. Mystics claim that it is possible to do something similar for this reality. It's all "I," where "I" ultimately points at something some might call "God." Hence the common instructions to look very carefully within.