OK, I'd be interested to see what you make of this:
Let’s say my mind is copied while I'm alive, and loaded into you while I'm in the room. There are now two people "running" my mind, yes? Now you leave the room. Where do I perceive myself to be, in the room or outside? In the room, of course – my awareness/perception does not transfer to your body or mind. Now let’s say I'm killed in the room. Does my awareness transfer to you then? Nope, it dies. I have no more thought, no sensory input, no experience -- nothing. You do, and as far as you are concerned, you are me; but from my perspective, my "stream of consciousness" is over for good.
Assuming you don't contest any of that, why is that scenario any different from what would happen if I died and my mind was then awakened in your brain? I contend that it isn’t. The stream of consciousness of the original ends, and if he has bought into this download as a way of cheating death, then he's bought a dud.
Again, you're adding things in there that don't exist. 2+2=4, not 5.
Two physical bodies (hardware), each with an identical copy of the same mind (software). They are separate and distinct. 'You' perceive with your physical eyes, while filtering events through 'your' thoughts and experience. 'I' perceive with my physical eyes, while filtering events through 'my' thoughts and experience. Anything you experience after the copying is unique to you, likewise, anything I experience after the copying is unique to me.
Wondering about "where you perceive from" or any of that is like asking if you install Word on your PC will it appear on my PC. They might ship from the factory as nearly identical copies of the same thing, but that doesn't imply a connection of any kind.
The trouble is the terms. We don't really have terms for what we're talking about. "You" and "me" as commonly used not only imply physical distinctiveness, but experiential and mental distinctiveness. In this case we're taking the physical differences out of the equation, leaving only the mind.
If our minds are identical (contain all the same information, experiences, thoughts, feelings, emotions, etc) then they are the same mind. However, we are located in two separate places, and experience things from different angles, in a literal sense. You sit
over there, while I sit
over here. But we would filter our perceptions through two instances of the same lens, as we have two copies of the same experiences. Nothing you experience has any effect on my experiences, nor do mine effect yours.
Now, any experiences gained since the copying are lost if that instance of the mind is destroyed. But 'you' don't die, as 'I' am a nearly identical copy with all the same life experiences up to the copying. That which is the person, the personality, the experiences the thoughts, feelings, and emotions continue on as they're all simply a function of the mind. The only things unique to you are those few memories formed since the copying.
That sense of self, sense of self-awareness, that 'me-ness' you seem to be groping for is simply a function of the mind. We would both feel the same way. We would both say "I am Fishbowl Helmet," and we'd both be right. Any quantifiable measure of personality would exist beyond the 'death' of one instance of the mind. But, an identical mind--or nearly identical mind--would continue to exist.