I think I have to at least graduate before anyone besides me is allowed to write a thesis on my wacky opinions on personal identity ;)
In a nutshell, I think persons just are continuous self-aware experiences, and that it's possible for two objects to be numerically distinct and personally identical. For instance (assuming I'm not a brain in a vat myself) I could be personally identical to a brain in a vat while being numerically distinct. The upshot of being personally identical to someone is that you are indifferent between "yourself" and the "other person". For instance, if Omega turned up, told me I had an identical psychological history with "someone else" (I use terms like that of grammatical necessity), and that one of us was a brain in a vat and one of us was as she perceived herself to be, and that Omega felt like obliterating one of us, "we" would "both" prefer that the brain in a vat version be the one to be obliterated because we're indifferent between the two as persons, and just have a general preference that (ceteris paribus) non brains-in-vats are better.
Persons can share personal parts in the same way that objects can share physical parts. We should care about our "future selves" because they will include the vast majority of our personal parts (minus forgotten tidbits and diluted over time by new experiences) and respect (to a reasonable extent) the wishes of our (relatively recent) past selves because we consist mostly of those past selves. If we fall into a philosophy example and undergo fission of fusion, fission yields two people who diverge immediately but share a giant personal part. Fusion yields one person who shares a giant personal part each with the two people fused.
In a nutshell, I think persons just are continuous self-aware experiences, and that it's possible for two objects to be numerically distinct and personally identical.
I've found this position to be highly intuitive since it first occurred/was presented to me (don't recall which, probably the latter from Egan).
One seemingly under-appreciated (disclaimer: haven't studied much philosophy) corollary of it is that if you value higher quantities of "personality-substance", you should seek (possibly random) divergence as soon as you recognize too much of yourself in others.
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