The inspiration for this question came from a very old memory of mine. I hardly remember much before the age of 5. But I do have a few fragments of memory from this time. One particular memory is when I am about 2 or 3. Basically I am in a shopping mall with my mother and her brother’s wife, my aunt. I don’t remember too much. But I seem to recall we did alot of walking.
Now this memory is obviously unique to me. No one would deny that it is my memory. But here is where it gets very philosophical: Am I the same person I was then? And FYI, I define being the same person as having at least most of the same brain material I had then, let’s say at least 51%. (I don’t know how the rest of you feel, but I believe our humanity lies in our brain. After all, if it were possible to transplant our brain into another body, we’d be the same person–right?)
And as long as I am asking the question, let me throw in “Are we the same person from moment to moment?” for good measure. (Please keep in mind the criteria I gave [same brain], but if you must, include your own too.)
Yeah, I don’t quite grok the OP either. Are you asking whether 51% of the brain cells you now have were present umpteen years ago–ie, are you “the same” in a strictly physical sense? What’s to debate about that? I don’t know the answer, but one of the science folks will be along shortly to enlighten us…
ETA: After the above clarification, I think the answer is no. You lose particular molecules when you bleed, excrete, cut hair/toenails etc.
The common sense answer is that since we are always a blob of matter that is fairly distinct, yes we are the same person from moment to moment. But this has nothing really to do with the matter in the blob.
I don’t think we’re our brain material. Living things (and quite a few non-living things, like rivers) are a continual process. We replace a lot of our cells many times over the course of our lives, and I’d guess that if you look at the actual atoms/particles, those get replaced even quicker. I’m not a biologist, but as far as I know even brain cells die off and get replaced in healthy people, though I’m not sure at what rate.
I guess what I’m getting at, is that people are a relatively fluid process and as far as material goes, it doesn’t really make more sense to say that a person is the same from day to day than it does to say that of a river or a fire. I think the matter (heh) gets in some ways even more confusing once you start to get into personalities, or god help us, “souls”.
We are the same entity in a similar sense that McDonalds is the same company it was yesterday, last year, a decade ago - even if all of the components eventually change, there is continuity of purpose and arrangement.
But we do undergo a continuous scheme of transition and change - not just in our physical matter, but in the way we think, the sum of our experiences, fears, prejudices, thoughts, opinions, memories, etc - some of them may be more persistent than others, but many are subject to revision, replacement, loss or abandonment.
But I believe that scheme of change is what we are - it’s precisely because one moment is not like the next, that we are able to experience, think, feel, etc. Change is not the enemy of our inner persons, it is what makes them possible in the first place.
Actually, now that I’ve thought about it a bit more; there’s nothing physical that I can think of that isn’t like that. Even mountains grow and recede, and stars get formed from gas, spewing matter everywhere, suck in new mass and eventually collapse/explode. Nothing stays the same, if you look at it closely enough, or take enough time.
That’s the Buddhist approach, that there is nothing continuous, but at the same time that gives an excuse to say that the continuity between all these different experiences and the way remembering one affects the next, does amount to setting a continuous I up, even though we should recognise it as a convenient fiction to link our experiences as something continuous to learn from.
Thought I’d throw out my own experience, as this is a philosophical consideration for me.
I have a disease in which my immune system goes, “num num num”, chewing up my brain and my nerves (MS). Some parts of me don’t work the way they used to, or don’t work at all, and there have been definite changes in my sensory systems which have changed the way my body feels to me. Like, my proprioception is impaired (I think that is the name of the related sense), so my body doesn’t feel like one thing anymore, nor do my body parts feel “right”. Hard to explain.
Anyway, even though things have changed so much for me, I still have a sense of myself as a person that is the same. This was a surprise to me to discover, and a relief.
I can’t really contribute to a discussion about the meaning of “the same person” as insightfully as others have in this thread, but I can address what it might feel like. Don’t know if this is relevant to the discussion, though…
How do you define who you are? Are you a continuum of events that you consciously experience? Are you the image of how the world sees you, your appearance, your personality, your beliefs and prejudices? Are you capable of changing who you are?
For example, back that 2-year-old you used to be – do you still crap yourself? Stuff random objects in your mouth? Scream bloody murder when you don’t get your way? If not, then I’d posit that you’re not the same person anymore, even if you remember being someone else many, many years ago.
Here’s where I like to use Bruce Willis’s quote from 12 Monkeys, while he’s watching the movie Vertigo: “The movie seems different, but that’s impossible, because the movie doesn’t change. It only seems different because I’m the one who has changed.”
Brain neurons, like the egg cells in a woman’s ovaries, are finite at birth and do not multiply or divide like regular cells, they aren’t replaced when they die off. That’s why people inevitably have trouble remembering things as they age, in addition to…umm, forgot what I was gonna say next.