What is "You"

What if a different sperm had reached the egg? Different DNA, different person, or not? What are the edges of your "self".

DNA

If identity is genetic code, then you're defined by a specific sequence of nucleotides. But change one base pair out of three billion and you'd still feel like yourself. Change a thousand, probably the same. So where's the threshold? There isn't one.

Boundaries

Try to locate what makes you distinctly you—not your personality, memories, or body, but the underlying subject having experiences. That core. The more precisely you look, the harder it is to find.

Schrödinger put it this way: imagine a man sitting in your exact spot a century ago, watching the same glaciers, feeling the same awe. He was born, suffered, felt joy. Was he someone else? What would make him definitively not you?

His answer: the self isn't a fixed thing. It's more like a canvas—a surface where experiences collect. The canvas might be the same one, running through everyone.

Conclusion

If there's no hard boundary separating your consciousness from others, the question "what if I'd been born as someone else?" starts to dissolve. Not because it's meaningless, but because the premise—that you're a sealed-off entity who could have been someone else may be wrong.

You're not watching the world from behind your eyes. You are the world, looking.