I was sorting through the pile of old Lego I had picked up from my parents today, and tripping on my childhood self. I haven't seen these little pieces of plastic in 25 or 30 years, and there are some pretty rare bricks in there, from what I can tell. There is also evidence of my former self - little bite marks in some of the bricks, bits of other toys and models, the odd hair or torn paper. It brought to mind the notions of self I studied in metaphysics.

Am I truly the same person I was? Cartesian logic would swing in favour of a 'yes', as I occupy the same space I once did - my body has staked out a chunk of real estate, and despite the flow of atoms in and out of my body, there is an unbroken chain of extension from my past to my present. This brings to mind 'the ship', a thought experiment where a sailing ship is built and christened, and throughout it's service period every piece of it is replaced, until no original piece remains. Is it the same ship?

My usual answer to this is that it depends on what you're talking about - if you mean is it physically the same ship, then the obvious answer is no. In Cartesian terms, it is, as there is no break in the extension of the whole (but arguments could be made to say that, overall, the extension was broken - whatever); I tend to lean towards the notion that a ship is an idea, a concept, and that the concept remains unbroken despite the alteration of the mass. Here's where the thought experiment gets sticky for me: the ship has no idea of itself, it is not a thinking thing (Spinoza aside). I am a thinking thing, and is my idea about myself unchanged (and the same for my parents' idea about myself, and any childhood friends I had who might meet me again - would they say, "Wow, you've really changed!", or, "You haven't changed a bit!")?

Or is it my DNA that remains unchanged, that prime map that says, "A b3ar shall be formed thusly, and so"? Is that the true identifier of self, a changeless idea of flesh in every cell? Kind of frightening to think it's probably true, and that the careful persona of "me" that I have crafted is probably irrelevent to that double-helixed gob in my core.

Buh. I shake my head and go back to organizing Lego.