>>> The person you are today doesn’t share a single cell with the version of you from seven years ago. (This is, of course, a generalization as some cells regenerate much faster and others a little slower.)
No, that is not even remotely true. Most of the neurons in the central nervous system (the part of the body one could argue does the most of thinking) stay mostly the same from adulthood to death[1].
I once heard that this is an oft repeated myth, that neurons are not replaced throughout life.
It seems to me to that what you said is true, but for some odd reason I have a recollection of reading a debunking of this. Does anyone know what I might be thinking of?
At the moment, the consensus seems to be that some neurons[*] are occasionally born in adulthood (e.g., in the hippocampus), but there’s a lot less agreement on why or if this matters at all. It could be the remnants of a prenatal process or a neat method for providing “pointers” into memories.
* In the brain itself. It is widely agreed that olfactory sensory neurons turn over every month or two, but they almost have to because they’re exposed to all sorts of junk in the air and wouldn’t survive a lot longer anyway.
> I recently spoke with a friend who was still dwelling on something that happened thirty years ago. “Why do you care?” I asked him. “That was four versions of you ago. That person doesn’t exist anymore. Move on.”
Do you think this actually helped your friend? In any way?
Of course! It helped your friend realize what kind of person you are and hopefully spurred them to find better friends who possess actual human empathy.
Without resorting to metaphysics, “I” am a slowly-but-constantly changing set of experiences, memories, predilections and preferences that happens to be instantiated in and associated with a particular physical body. My relationships with other people tend to be the most important things to me and the things that most shape whatever direction my identity is going.
My body is not the same exact set of cells or molecules that I was 30 years ago. But I’m like the Ship of Theseus- the essence of what I am is a direct consequence of my formative experiences regardless of what pieces I’m built of at any given moment.
It’s my choice (within the constraints of how brains work) of how much I let past experiences affect my current behavior. But I can’t forget those experiences and if I could, then I would not be the same “me” in a much deeper sense than just having different cells or molecules.
It feels so strange to read blogposts like this in 2025. The level of mediocrity makes you question if this has been created by a human or an ai bot. Next you start questioning yourself why you still look into your smartphone like a junkie.
So if Theseus was aboard his ship for many years it would add another layer of it that ship still is his own?
In Vernon Vinge’s A Fire Upon The Deep you have pack of dogs that are not so smart individually, but they had a pack personality that was smart. Even (for one case in the book) the dogs could be replaced but the personality remained.
Changing individual cells doesn’t change what is the you of your consciousness and memories. Of course, even without cell replacement you change with time, new memories, insights and so on, but both changes happen at different abstraction levels.
Peter F. Hamilton's Pandora's Star contains a wonderful variant of this thought experiment: in the future he describes, memories are editable; so it's possible to commit a crime, like murder, and then wipe all memory of it, so that you are, from your own perspective, innocent. The justice system, of course, says otherwise. The metaphysics (whether or not it's possible to step into the same river twice) don't matter. Technological advancement dictates the answer to the philosophical question about continuity of the self and guilt.
Depends a lot on the mistake and your life since then. Is it something you could still fix today? Is it a mistake you keep repeating? Is it a huge mistake that still directly impacts your relationships and today in some way?
I think mistake is an overused word, and a choice that qualifies as a mistake in the future may not be judged as a mistake now.
Simply put... we make choices based on the information we have now. And our future judgment of our choices should account for the information we had back then, most of which has probably been forgotten.
But to answer your question, we shouldn't regret our mistakes but it is very good to remember them.
I think the correct answer in terms of mental health is: as little time as possible.
The actual answer is more complicated. Someone who got locked up for 25 years knowingly committing a significant crime might regret it for the majority of their sentence, at least.
I'm reminded of the SMBC comic https://www.smbc-comics.com/?id=2722 which resonated with me. If it takes ~7 years to master something, you should dedicate yourself to becoming good at it. Or at least you don't have to tie your identity to what you do you right now; you can reinvent yourself and experience more from of life, but you have to give yourself the time to do so.
It's been almost 14 years since that was published, so maybe some self-reflection is due.
Readit News
No, that is not even remotely true. Most of the neurons in the central nervous system (the part of the body one could argue does the most of thinking) stay mostly the same from adulthood to death[1].
[1]: https://en.wikipedia.org/wiki/Neurogenesis
(With an understanding that where you are now undoubtedly sucks. My sympathies.)
It seems to me to that what you said is true, but for some odd reason I have a recollection of reading a debunking of this. Does anyone know what I might be thinking of?
At the moment, the consensus seems to be that some neurons[*] are occasionally born in adulthood (e.g., in the hippocampus), but there’s a lot less agreement on why or if this matters at all. It could be the remnants of a prenatal process or a neat method for providing “pointers” into memories.
* In the brain itself. It is widely agreed that olfactory sensory neurons turn over every month or two, but they almost have to because they’re exposed to all sorts of junk in the air and wouldn’t survive a lot longer anyway.
Abstract thing A you can never measure gives you joy and renewal
Abstract thing B you can never measure holds you back and limits you
The practical difference is zero or near zero, so go and be joyful and happy!
Dead Comment
Do you think this actually helped your friend? In any way?
Without resorting to metaphysics, “I” am a slowly-but-constantly changing set of experiences, memories, predilections and preferences that happens to be instantiated in and associated with a particular physical body. My relationships with other people tend to be the most important things to me and the things that most shape whatever direction my identity is going.
My body is not the same exact set of cells or molecules that I was 30 years ago. But I’m like the Ship of Theseus- the essence of what I am is a direct consequence of my formative experiences regardless of what pieces I’m built of at any given moment.
It’s my choice (within the constraints of how brains work) of how much I let past experiences affect my current behavior. But I can’t forget those experiences and if I could, then I would not be the same “me” in a much deeper sense than just having different cells or molecules.
In Vernon Vinge’s A Fire Upon The Deep you have pack of dogs that are not so smart individually, but they had a pack personality that was smart. Even (for one case in the book) the dogs could be replaced but the personality remained.
Changing individual cells doesn’t change what is the you of your consciousness and memories. Of course, even without cell replacement you change with time, new memories, insights and so on, but both changes happen at different abstraction levels.
It’s a metaphor.
> still dwelling on something that happened thirty years ago.
Exactly that: clinging causes suffering.
Buddhism also goes a step farther, they have a whole doctrine about emptiness and no-self: there's no permanent or unchanging self to be found.
"Those who ignore history are doomed to repeat it" as they say, even it was over 7 years ago...
Simply put... we make choices based on the information we have now. And our future judgment of our choices should account for the information we had back then, most of which has probably been forgotten.
But to answer your question, we shouldn't regret our mistakes but it is very good to remember them.
The actual answer is more complicated. Someone who got locked up for 25 years knowingly committing a significant crime might regret it for the majority of their sentence, at least.
It's been almost 14 years since that was published, so maybe some self-reflection is due.