When a child is born, it has no concept of a self, and therefore no concept of a division between itself and the rest of the world. As it explores the world, it begins to collect information, which compresses to the shorthand of biological memory.
This shorthand is of connections made between experiences, noting that they share a similarity. These single recordings of similarity blossom and interconnect into groupings, and as we endure new experiences we connect them with groupings already created. Thus we learn and refine the words that describe divisions - of like/unlike, up/down, outside/in, on/off, hot/cold, light/dark.
These detatch from any single observation, and become concepts. We employ these concepts, in forming a description of the self. And inevitably, we create the self in the image of our chaotic, long-evolved, biological core, because that form is the ONLY form in which the concept of a 'self', divided from the rest of existence, has any meaning.
So the self is in the body, in the behavior. The self is on the inside of the sense organs. The self is our desire for breath, and our drive to explore, and our overdeveloped sense of empathy.
The self is anything that doesn't require the act of observation to be real.
Over time, our sense of self solidifies.
And here comes a smug philosopher, to lecture us about "virtual" reality versus "real" reality. To dismay us with his declaration that, if our senses were bypassed well enough, we could be jacked-in from birth to some false illusion of freedom while our real selves lay shackled to an iron rack of slavery somewhere else. That if our brainstems were tickled with electric probes in just the right way, our minds would be convinced that our bodies are somewhere they are in fact not.
BUT THIS ALL BEGS THE DEFINITION OF A SELF. If you have not learned a sense of self, how can YOU be fooled, by alleged "false" sensations, when there has not been defined a YOU to be fooled?
Put your brain in a tank, and zap the eyesockets with careful voltages that simulate an optic nerve ... Are your eyes being fooled? What eyes? The largest betrayal in effect, is that your brain thinks you still have eyes. But if you were born in a tank, and never had them, where is the injustice?