A very early memory of mine is staring, head back, up at a tree. I remember, in a fuzzy way, the dichotomy between the details in each minutely detailed leaf, and the whole, indivisible mass of green. I was being babysat by an aunt; my cousin was in his room for some transgression. I think it was summer: I remembered being impressed by the warmth and beauty around me.
It's not a remarkable memory for the vista, I've seen that tree hundreds of times. Rather, it stayed with me because it was the first time my mind stumbled across a mystery that's been with me ever since. I was outside, observing manicured nature. My cousin was in his room, probably fuming at his mother. But why was my experience of the world the one looking at the tree? My cousin must certainly have this same first-person experience, feeling one individual's pain, beholding one individual's sight. I knew I was me, it's basically a tautology. I didn't doubt I was the individual named Paul Barba, but it felt so arbitrary that I shouldn't be my cousin, or my neighbor, or any of 6 billion other individuals.
It's a hard question to ask, because there's a simple question obscuring a deeper one. I am me, because I have to be somebody. That's just how the world works: each person is an individual. There's no explanation necessary, and any perceived asymmetry is just a lack of perspective on my part. But at the same time, the huge divide between Paul's experiences and everyone else's, from my point of view, was troubling as a child.
Ultimately, I think the question is one of consciousness. That was the asymmetry in the world I was detecting, but too young to really understand. Everything else is physical. My cousin, the tree: they were all physical objects describable with reference to atomic patterns. But what about this perception of the world I had? This self-understanding mind, conscious of the passage of time around it? We still don't know how to understand it, really, in terms of electrons and photons. Maybe it's the work of a soul. Maybe solipism is truth, and there is a fundamental divide between me and everyone else. But I'm inclined to believe it's ultimately a matter of matter and energy.
I was Paul at age 7. I'm Paul now, and if it's meant to be I'll be Paul 50 years hence. There's this continuous stream of awareness that links the experiences of that child staring at a tree with the young adult typing on a laptop. I don't doubt that I was experiencing that tree.
But so much has changed: my brain has grown and reformed its patterns since then. Neuroplasticity tells us that the patterns in our brain are constantly changing. Most of my cells have died since then, being replaced by new generations. With twins, you could have argued that twin brothers at 7 are more similar than the 7 year old version and the 40 year old version of the same person. But the 40 year old and the 7 year old share a linked experience of being one person...
Which leads me to believe that it's just the uninterrupted existence of Paul that leads me to connect my current experiences with that child's experiences. I've got memories, but those aren't the same as a real experience. 7 Year old Paul experienced consciousness, 24 year old Paul is experiencing consciousness: everybody is. Memories, opinions, the chemicals rushing past our neurons are just incidentals. My perception of me, my intelligence and opinions, is less fundamental then this experiencing of looking out of two eyes: that's what I relate to as me, more deeply then the realities of a single moment.
Which all, ultimately, leads me to believe that what I would most deeply connect to as myself, the core of being, that thing experiencing emotions and visions and the pinch of the cheeks during a smile and the wind blowing through your hair: that wasn't limited to the boy looking at a tree. Whatever natural phenomenon leads me to perceive the world instead of blindly reacting to physical laws is at work in everybody. Thus while at one level I am Paul, I also believe I'm everyone else, everyone who will exist, at least until humanity dies off or evolves past my experiences. It doesn't feel true, at a level. I still feel, and am, closed off from every other experience. But that division of the world into individual pockets of consciousness doesn't mean they aren't all, in an important way, the same. When I die, these thoughts will be gone, these experiences forgotten, but experiencing and thinking will persist. What I thought was my own first-person experience will continue peering out some billions of pairs of eyes.