I found myself poring over the Wikipedia entry for the Ship of Theseus the other day. If you're not familiar, it's basically a thought experiment along the lines of "if a given ship's parts are replaced at every port it visits, and eventually none of the parts are from the original ship, is it still the same ship?" The thought experiment questions the meaning of identity of a whole composed of many individual parts, such as a ship, or even a human.
I thought about this while I was digging through time (read: old posts) the other day. In all these years I've been blogging, I don't feel like I've fundamentally changed, I still feel like I'm the same person I was back then writing those posts, and yet at the same time I know I've grown and adapted in many different ways.
People change over time of course, but in terms of identity I tend to think of it as something like a codebase that undergoes version control. At any given point of time there is a version of you, slightly different from who you were yesterday or who you will be tomorrow, but still fundamentally the same. As time passes, the person you are adapts to the path and circumstances you travel, resulting in the next versions. All of this reminds me of this quote:
"No man ever steps in the same river twice, for it's not the same river and he's not the same man." - Heraclitus