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Comment by IggleSniggle | Hacker News Reader

Meh. That’s what we do everyday as our body sheds old cells and grows new ones. It’s the ship of Theseus already anyway. The me of yesterday is dead. The me of today only believes I am the same.

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Not an expert on the subject at all but to my knowledge not quite. Yes, this applies for most cells in the body but in the case of neurons and glial cells, they stay for decades, so in a real, practical sense, the you of yesteryear is still the you of today right down to the cellular level where it most matters in the brain.

Not only that, there's a difference in repairing a ship over time and swapping out all its parts at once. I'm pretty sure most people would consider the second scenario a new ship.

With cars, there's a distinction between a "restoration" and a "survivor". A survivor hasn't had things done to it other than maintenance.

There's debate about where the line is between a "restoration" and a "replica".

On that distinction i'm not sure I agree, if in both cases all parts of the ship have been replaced, the difference between doing it all at once and gradually is a semantic one, with rejection of the "new" ship as the same thing as the old ship being more of an emotional reaction. In either case, it's somewhat separate from what I mentioned about the cells in the brain and how they do stay the same over decades even if others in the body change just like the parts of the ship. Like I said though, that needs a bit of further confirmation because the science seems a bit ambiguous on the details.

I don't think the difference is as trivial as you think. When you replace things slowly there are shared experiences for those parts. They have commonality among them. When you replace something instantly there is no shared experiences or commonality.

This is an interesting point that I hadn't quite considered. Not sure how it would apply on the scale of inanimate objects but I could see it being relevant to a macroscopic organic system with consciousness, like our brains and bodies.

Well the analogy was directed at macroscopic organic systems with consciousness.

But with Theseus's ship we can see a similarity. If we had a ship, tore it down, then built a new ship without using any parts from the old ship, every sane person would call that a different ship. Frankly, the tearing it down step isn't required (an important factor). Conversely, if we repair a ship over time we do consider it the same ship. Maybe this is just personifying objects, but these conclusions about new ship/same ship would be pretty standard. It is why we distinguish replica and restoration.

If it were possible to swap out a ship with an “identical” replica instantaneously (I’m not sure what the benefit would be) I think most people on board would consider it to be the same ship. And, for that matter, it’s relatively common for ship owners to name their ships after the prior ship that held the same function, as if it was the same ship, even when it’s a totally different make/model!

But instead of swap make an identical copy. You now have two ships.

This reminds me of relics in the Catholic Church. An object held by a saint gains divinity due to their commonality, and being in the presence of that divine object passes along the divinity once again.

And the whole point of the thought experiment is to show that such a distinction is meaningless.

I'm not quite sure. There's multiple scenarios here. If we upload your consciousness into a computer and you're still alive, then there's multiple entities. If we replace your organs with machinery over time, then there is only a single entity that is changing. The latter is like the ship, but the former is not.

This is a really interesting point. From an economic perspective, I’ll say that if there are multiple entities, it dilutes the rarity of the original, and thus it is no longer the same. Destroying the original maintains the entity’s relationship to all external entities, preserving not only the original, but the original’s place in the system.

So by that reasoning, if we upload your consciousness into a computer and make sure we destroy you before we activate it, same difference right? We've just made the "slow replacement" process significantly more efficient.

I'm not sure if you're trolling, willfully missing the point to be contrarian (trolling), or just missing the point. Multiple entities makes a distinction in this thought experiment.

I didn't think brain cells were replaced.

That used to be the dominant theory - there is now evidence that new cells continue to grow - just the replacement rate slows down as we age. However we still do not really understand the mechanisms of neurogenesis (growth of new brain cells), the interplay with neural stem cells, cellular development dependencies or the pathological mechanisms associated with various diseases such as Alzheimer's. There continue to be new theories, emergent lab work etc but we still have a long long way to go before we have a clear insightful model of the mechanisms involved, never mind a predictive understanding for systemic outcomes.

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