I feel like this is just a totally stupid question.
The brain has inputs, internal processing, and outputs. The conscious experience happens within the internal processing.
If you make a second copy, then that second copy will also have conscious experience, but it won't share any inputs or outputs or internal state with the first copy.
If you were to duplicate your computer, would the second computer share a filesystem with the first one? No. It would have a copy of a snapshot-in-time of the first computer's filesystem, but henceforth they are different computers, each with their own internal state.
You could argue that there are ways to do it which make it unclear which is the "original" computer and which is the "copy". That's fine, that doesn't matter. They both have the same history up to the branching point, and then they diverge. I don't see the problem.
When you replace "I" with "it" (as in your example with computers) the question becomes meaningless and stupid. As an outside observer both computers are the same, as they act exactly the same way, therefore there is no question. That is actually the "egalitarian" view in Benj Hellie's paper [1]:
> The ‘god’s eye’ point of view taken in setting up the egalitarian metaphysics does not correspond to my ‘embedded’ point of view ‘from here’, staring out at a certain computer screen.
The vertiginous question (or Nagel's Hard Problem [2] to a degree: Why does physical brain activity produce a first-person perspective at all?) is about the subjectivity of consciousness. I see the world through my eyes, therefore there is only one "I" while there are infinitely many others.
The duplication example was something I made up to explain the concept, but to reiterate, if I could make a perfect copy of me, why would I still see the world from the first copy's eyes and not the second, if the physical structure of the brain defines "me"? What stops my consciousness from migrating from the first body to the second, or both bodies from having the same consciousness? Again, this question is meaningless when we are talking about others. It is a "why am I me" question and cannot be rephrased as "why person X is not person Y".
Obviously we don't have the capacity to replicate ourselves, but I, as a conscious being, instinctively know (or think) that I am always unique, regardless of how many exact copies I make.
As I mentioned in another comment, I don't have a formal education on philosophy, so I am probably doing a terrible job trying to explain it. This question really makes sense when it clicks, so I suggest you to read it from a more qualified person's explanation.
Right, yes: Why does physical brain activity produce a first-person perspective?
We might ask "what else do we expect it to do?" A second person perspective makes even less sense. And since the brain's activity entails first-person-perspective-like processing, the next most obvious answer, no perspective at all, isn't plausible either. It's reasonable that the brain would produce a first person perspective as it thinks about its situation. (And you don't have extend this to objects that don't think, by the way, if you were thinking of doing that.)
But I'm still left with the impression that there's an unanswered question which this one was only standing in for. The question is probably "what is thinking, anyway?".
Or, something quite different: "Why don't I have the outside observer point of view?". It's somehow difficult to accept that when there are many points of view scattered across space (and time), you have a specific one, and don't have all of them: "why am I not omniscient?". It's egotistical to expect not to have a specific viewpoint, and yet it seems arbitrary (and thus inexplicable) that you do have one. But again, the real question is not "why is this so?" but "why does this seem like a problem?".
> if I could make a perfect copy of me, why would I still see the world from the first copy's eyes and not the second, if the physical structure of the brain defines "me"? What stops my consciousness from migrating from the first body to the second, or both bodies from having the same consciousness?
If you define consciousness as the stream of perceived experiences coming from the physical body (sights, sounds, touch, and even thoughts, including even the thought that you're in control), it's expected each body would have its own consciousness? The OP article about split-brain experiments also (very counterintuitively) indicates that at least some thoughts are perceived rather than something you're actively doing?
Personally, my answer to “why am I me” is similar to the anthropic principle. If you were anyone else, you would be asking the exact same question, and if you were nobody, you would not be able to ask the question. By asking the question, you must necessarily be somebody, and the question would be the same no matter which somebody.
Your answer works when you are observing the person(s) from outside, referring to a third person (A and B are both conscious, so it doesn't matter which one is which). However, it doesn't answer when one of the subjects is "I", because I and everyone else is clearly different (hence the title of Benj Hellie's paper I linked above: Against Egalitarianism):
> The ‘god’s eye’ point of view taken in setting up the egalitarian metaphysics does not correspond to my ‘embedded’ point of view ‘from here’, staring out at a certain computer screen. The god’s eye mode of presentation of the Hellie-subject and the embedded mode of presentation of myself are different: as different as the manifest and scientific modes of presentation of water—indeed, perhaps even more so: that is the core of the Humean worry. So it is not a priori that any of those subjects is exactly the same thing as me. And if not, if I am told that it is this one that is me, I want to know why that is.
No, only you will refer to yourself as "I". The other one will call themselves "I" but it's not the same "I" as you. For all we know you are not even sure that the other one is really a conscious being or a robot powered by an AI that could pass the Turing test [1].
> I still don't see what is difficult about this.
You have been dismissing two of the most profound questions of philosophy, and unfortunately I am not able to explain the questions (let alone attempt to answer them) any better. There is some serious philosophical and neurological research [2] related to this subject. Maybe you should spend some time yourself researching the literature.
The brain has inputs, internal processing, and outputs. The conscious experience happens within the internal processing.
If you make a second copy, then that second copy will also have conscious experience, but it won't share any inputs or outputs or internal state with the first copy.
If you were to duplicate your computer, would the second computer share a filesystem with the first one? No. It would have a copy of a snapshot-in-time of the first computer's filesystem, but henceforth they are different computers, each with their own internal state.
You could argue that there are ways to do it which make it unclear which is the "original" computer and which is the "copy". That's fine, that doesn't matter. They both have the same history up to the branching point, and then they diverge. I don't see the problem.