Poll: Which ship is the Ship of Theseus?
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The museum's ship
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The "Ship of Theseus" thought experiment
#1
Cross-posted from the old board:
https://www.tapatalk.com/groups/the_coff...=27&t=2880

The "Ship of Theseus" paradox centres an ancient ship in a museum, that has had each of its planks replaced one by one, as the originals have rotted away. It's like the old tale of the "grandfather's axe": someone claims to still be using the same axe as their grandfather did, but it's had both the handle and the head replaced multiple times over the years, so is it really the same axe? Or, in more abstract terms: if an object has had all of its component parts replaced, is it still fundamentally the same object?

We can take this even further. Let's say that, after all of the planks have been replaced, a shipbuilder gathers together all of the original planks, and rebuilds them into a complete ship. We now have two ships: the museum's ship (which has had all of its planks replaced), and the shipbuilder's ship (which uses all of the original planks). Which ship, if either, is the original Ship of Theseus?

In the following video, philosophy professor Jennifer Wang offers some possible solutions to the "Ship of Theseus" case:



It's worth watching this 8-minute video, to understand the philosophical problems that this case poses - but, essentially, it boils down to an apparent conflict between two seemingly self-evident principles:

A) Ordinary objects survive gradual change;
B) An object is defined by its component parts (at least, when those parts are in the same arrangement).


Now, the proposed solutions to this apparent contradiction are as follows:

  1. Accept Principle A, and deny Principle B. This resolves the apparent paradox, in favour of the museum's ship (even though it has none of its original planks). However, this means the shipbuilder's ship is not the Ship of Theseus (even though it uses all of the original components).

  2. Accept Principle B, and weaken Principle A. We could say that everyday objects survive some gradual change, but only up to a point. For example, we might say that the museum ship is still the original Ship of Theseus until over half of its planks are replaced, at which point it no longer is. However, Principle A is based on the idea that a ship is not meaningfully different after a few planks have been replaced - so, surely, a ship with just over half of its original planks is not meaningfully different from a ship with just under half of its original planks? Whatever cut-off point we pick is going to be arbitrary.

  3. Accept Principle B, and deny Principle A in its entirety. This resolves the paradox, in favour of the shipbuilder's ship being the Ship of Theseus. However, this means that the museum's ship ceases to be the Ship of Theseus, even after one plank has been replaced.

  4. Accept both principles. This means that both the museum's ship and the shipbuilders ship can claim to be "The Ship of Theseus". However, this means we need to reject the logical principle that "if X=Y, and Y=Z, then X=Z" - because otherwise we could argue that "The museum's ship is the Ship of Theseus, and the Ship of Theseus is the shipbuilder's ship, so the museum's ship is the shipbuilder's ship", which is clearly absurd!

  5. Change the way we think about the ships. Instead of thinking of 'ships' as three-dimensional objects, we think of them as four-dimensional objects, with three dimensions in space and one in time. Thus, one 'ship' starts as "The Ship of Theseus" and becomes "the museum's ship", while the other starts as "The Ship of Theseus" and becomes "the shipbuilder's ship". This way, we get to keep principles A and B, as well as the "if X=Y, and Y=Z, then X=Z" logical principle. However, it also means that, when we say "The museum's ship is the Ship of Theseus" or "The shipbuilder's ship is the Ship of Theseus", it's no longer clear what claim we're making.

So, what are your thoughts? Which ship, if either, is the Ship of Theseus? And is the grandfather's axe really the same axe?
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#2
This may just make the question even more tricky to answer, but doesn't the human body regenerate completely every 10 years? If so, could we apply the same principles and deny that we are the same person as we were 10 years ago. Do you cease to become yourself and adopt a new identity every 10 years?

Anyway, with that weird tangent out of the way, I think after a certain amount of the planks are replaced, rather than not being called the Ship of Theseus at all, the ship should rather be called a restoration of it. I completely disagree with the shipbuilder's ship being the Ship of Theseus, though. Once a ship has been broken down into its individual planks, it's rather lost its purpose as a ship. The shipbuilder's ship is a new creation - one could say it's derived from the Ship of Theseus, but I think it would be a massive stretch to completely break the ship, then rebuild it and claim you had built the Ship of Theseus.
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[-] The following 1 user Likes Pyrite's post:
  • Kyng
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#3
(05-06-2019, 01:29 PM)Pyrite Wrote: This may just make the question even more tricky to answer, but doesn't the human body regenerate completely every 10 years? If so, could we apply the same principles and deny that we are the same person as we were 10 years ago. Do you cease to become yourself and adopt a new identity every 10 years?

Yes, this is a very good point.

For me, this creates serious problems for solution #3: it suggests that I'm no longer the same person after one of my cells has been replaced. I accept that "CJ before one cell is replaced" and "CJ after one cell is replaced" are two distinct objects of thought; however, I'm absolutely not willing to accept that they refer to two different people. The "objects of thought" concept is so specific and restrictive that, in my mind, it fails to capture the "what-it-is" concept that we're interested in here.

Quote:Anyway, with that weird tangent out of the way, I think after a certain amount of the planks are replaced, rather than not being called the Ship of Theseus at all, the ship should rather be called a restoration of it. I completely disagree with the shipbuilder's ship being the Ship of Theseus, though. Once a ship has been broken down into its individual planks, it's rather lost its purpose as a ship. The shipbuilder's ship is a new creation - one could say it's derived from the Ship of Theseus, but I think it would be a massive stretch to completely break the ship, then rebuild it and claim you had built the Ship of Theseus.

Yeah, I agree with this too.

I think we need to be a little bit careful, because overhauling a ship would probably involve temporarily dismantling it to get at the insides - and I don't think this should destroy the ship (at least, not permanently). If a ship is taken apart temporarily to allow repairs to be carried out, then I'd consider the repaired ship to be a continuation of the original, rather than a new ship using original parts. This is getting at the "worm theory" from solution #5: the 'worm' might have a gap in the middle while the ship is being repaired, but it's all the same worm.

(On the other hand, the "shipbuilder's ship" in my original post would just be "a new ship using original parts", in my opinion)
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  • Pyrite
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#4
Well, I fell down this rabbit hole again today :P .

I began to have a thought which soon turned out to be ridiculous: could you do the same thing with languages? For example, if I started out with English, and replaced the English words one by one with French words, would there come a point where it turns from French-influenced English into English-influenced French?

Now, as I said, I quickly realised that this was silly. First of all, not all English words have a single equivalent in French: some might have multiple equivalents, and there are probably a few which have no equivalent. Secondly, even if we figured out a way to work around this, the 'language' we ended up with after "replacing every English word one by one" still wouldn't be proper French. At best, it would be high-school Franglais: the vocabulary would be French, but all other elements of the language (for example, the grammar) would still be English. After all, a language isn't just a bunch of words which can be added, removed, and re-ordered at will. It's how those words interact with one another that makes the whole thing work.

But, I still tried to save this analogy. I began to wonder: what if we applied French grammatical rules to all the French words, and English grammatical rules to all the English words? Obviously, such a thing would likely end very badly: we'd soon find ourselves with a whole bunch of contradictory grammatical rules where it becomes impossible to determine the 'correct' sentence structure. There wouldn't be any point where "French-influenced English becomes English-influenced French"; however, we probably would reach a point where "French-influenced English becomes a mangled, incomprehensible mess", and then another point where "that mangled, incomprehensible mess becomes English-influenced French". It'd be like trying to turn a car into a refrigerator by replacing one component at a time: for most of the 'transition', you'd have a heap of junk that was usable as neither. Not to mention, the transition from English grammar to French grammar would probably be quite jumpy: you wouldn't get the gradual change required for the 'Ship of Theseus' thought experiment to work in the first place.

Sorry about this: I had to write it down as an example of myself thinking I was being smart, when I really wasn't :lol: .
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