My memories are from that of a former self with whom I can no longer consider to be one and the whole the same as my present state. So then: Who am I?
The current thing which I define as “me” is a continually changing conglomeration of memories, thoughts, and objects which occupy space and time. Although I have memories of my past to remind me of who I once was, my future self is something I can’t even begin to describe beyond mere guesses.
People seem to intuitively hold a coherent view about ourselves and who we once were, are, and will be. But, as with most things, it’s a little more complicated than what we naïvely hold to be true. We are a framework of particles, molecules, and systems which move through time and space, with many of these things being partially or completely replaced over the course of our lives.
At face value do I consider myself to be the same person who was born years ago? Certainly. Can I point to any one thing and say “This is what has remained constant throughout”? Not exactly. Instead of trying to point to my body, brain, or appeal to a metaphysical soul, I look at the process of introspection itself to find who I really am.
It is the act of attempting to define who I am where I come to this conclusion: I am the sum of my parts. Although this sum is in constant flux, it persists through time and space.