The Ship Theseus

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Since I didn't see any threads on this (except maybe one post), I thought I'd start one to see what everyone's view is on this paradox. There have been many different variations of it, so I'll post the one I like the most....

Let's say there's a really old ship called Theseus. This ship is really famous; it had been in several movies and was even the scene of a crime when a famous rapper was shot and killed on it. Well, anyway, the ship is in need of numerous repairs. The owner finally decides to get it fixed, and docks it at the repair shop. After the mechanic starts repairing it, he realizes that the entire ship needs to be repaired, so he slowly starts replacing it bit by bit. Well, because of the ships fame, the mechanic thought it would be a neat idea to, instead of throwing away the old parts, build an identical ship out of the remains. So, as he's replacing the parts on the existing ship Theseus, he starts assembling the new ship Theseus. When he gets done, he has two identical ships; one made entirely out of new parts, and one made out of the old parts.

Which one is the real ship Theseus?

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@sthack99,

They both are. By calling both ships Theseus that means they are both ships named Theseus. This is much like having two different humans named John. The name is only a tool for identification.

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@sthack99,

If the two ships are identical, the one built with the old parts is the 'real' Theseus. Irrespective of the ship of new parts, if I take apart the Theseus then rebuild it exactly, it's still the real Theseus. Irrespective of what happens to the old parts, if I build a new ship of new parts identical to the old Theseus, it is not the 'real' Theseus (except to the extent, as Theaetus points out, it is called Theseus so has as much claim).

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@Theaetetus,

In The Fifth Elephant, Terry Pratchett says something which I think would be relevant here:

"In the fullness of time, it will be your descendants' axe. Fashions will change and the handle will be replaced; the head will dull and it will too have to be replaced...but even with the new handle and the new head, it will still be your descendants' ancestors' axe..." (I realize I probably mangled the quote, but that's OK...) In much the same fashion, I think that if you assembled all the outmoded and worn-out parts from the old axe and reassembled them, you'd get yet another ancestral axe which while in mode is easily recognizable from the traditional axe, in its essential nature, it is not. This fact, that it is possible for an extension of a Form to perfectly bifurcate in this way, is IMO part of what undermines the idea.

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@sthack99,

But is the new and improved ship Theseus the original ship? When the owner returns for his ship, should he take the new one or the one made out of the original parts? Which one does he rightfully possess ownership of?

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@sthack99,

Sorry, my response was to Theaetetus. Smile

I should have quoted.

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@sthack99,

If the owner paid for the new parts then the owner owns both of them. It is much like if someone takes their car into a mechanic to get fixed. They own the new parts and the old. Most of the time the owner has no use for the old part so they let the mechanic take care of disposal.

They are both real ships. Its not like one is a figment of the imagination and the other is real. If there is an identity issue then rename one of the ships to Cyclops or something else.

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@sthack99,

Ok, then let me ask you this...

Forget the names for a second. If the mechanic had decided to get creative and use the original parts to build a house instead of another ship, would the house be the original ship Theseus? Or would the original ship no longer exist?

Personally, I think this is a tough question to answer. What defines 'selfness'? What makes something itself? It's attributes? It's 'soul'? It's purpose for existing? I guess it depends on the person answering the question. At what point does one's self, whether it's a person or an inanimate object, become a completely different entity? At the exact moment you are pronounced dead, are you no longer you? Does your body define you, or your mind?

In the situation of Theseus, we know it doesn't have a mind. But does it have self? If you take your car to the repair shop to get fixed, are you driving away with your car, or a different one?

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@sthack99,

sthack99 wrote:

Ok, then let me ask you this...

Forget the names for a second. If the mechanic had decided to get creative and use the original parts to build a house instead of another ship, would the house be the original ship Theseus? Or would the original ship no longer exist?

But then he's no longer taking something apart and putting it back together again. Making a house out of a boat is recycling. Taking a boat apart and putting it back together... I don't think so.

sthack99 wrote:

Personally, I think this is a tough question to answer. What defines 'selfness'? What makes something itself? It's attributes? It's 'soul'? It's purpose for existing? I guess it depends on the person answering the question. At what point does one's self, whether it's a person or an inanimate object, become a completely different entity? At the exact moment you are pronounced dead, are you no longer you? Does your body define you, or your mind?

Ah. Then this is not a paradox from a physicalist point of view. I understand what you're saying: as the new ship is built, it is always, though decreasingly so, being built into the old boat. If you believe this thing being built into leaves some kind of presence or existence after the new boat is built, then you have a paradox. If you don't, there's none.

sthack99 wrote:

In the situation of Theseus, we know it doesn't have a mind. But does it have self? If you take your car to the repair shop to get fixed, are you driving away with your car, or a different one?

If it has changed it is different. But it was my car before and it is my car now. The boat built from the parts of the old boat is identical to the old boat and is made of the old boat... ergo it is the old boat. It shouldn't matter how you got there.

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@Theaetetus,

Theaetetus wrote:

If the owner paid for the new parts then the owner owns both of them. It is much like if someone takes their car into a mechanic to get fixed. They own the new parts and the old. Most of the time the owner has no use for the old part so they let the mechanic take care of disposal.

They are both real ships. Its not like one is a figment of the imagination and the other is real. If there is an identity issue then rename one of the ships to Cyclops or something else.

The point of this particular problem (and there's a Bike one, also) is the identity crisis. It's easy for you to say "Oh, just replace the name of the other ship Cyclops", since you have no sentimental attachment to either. However, in society, we do become emotionally attached to material objects, not to mention people.

Say this same dilemma occurred with two of your family members. Each person had different biological parts of one another -- Who's who, and would it be so easy for you just to shout, "Oh, that's Jim!"? And this is where the critical thinking starts: Are you a socially constructed and ascribed identity? Are you your body? Just what is identity?

Are both of those ships the *real* ship? Does the *real* ship not exist anymore in the way we initially perceived? Isn't their identity relative? Surely, just because they have the same parts, a majority could agree that only ONE is the ship. Would they be wrong for stating this? Perhaps identity has nothing to do with the material parts, but the immaterial notion of relation?

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@sthack99,

Meaningless question.

Identity is determined by the observer, not by the thing itself. Whats more is that names are arbitrary.

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@Mr Fight the Power,

Mr. Fight the Power wrote:

Meaningless question.

Identity is determined by the observer, not by the thing itself. Whats more is that names are arbitrary.

This question is not meaningless in the least. It invokes introspection, a critical look into who we are. That's far from meaningless, in my opinion.

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@sthack99,

The problem is that people are not simple material objects. Looking back at the OP, neither of the ships are the original ship. The ship with new parts may be identical to the original in every way other than the parts much like a new car is identical to the first model to come off the assembly line, and the reconstructed ship is a new ship constructed by the builder with old parts. Sure, they may be the same old parts, but it is a new ship built with the old parts.

I do not agree that looking at the identity of material objects forces introspection or a critical look into who we are, nor do I think the question is meaningless. Now if we were talking about talking about doing this thought experiment with humans, then I can see where introspection comes into play.

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@Bones-O,

Bones-O! wrote:

But then he's no longer taking something apart and putting it back together again. Making a house out of a boat is recycling. Taking a boat apart and putting it back together... I don't think so.

Remember, it's a gradual change, not just "taking a boat apart and putting it back together" again. If the mechanic stopped after replacing only one board, would it be the same ship? Or would you say the original ship is no longer in existence; instead you have a new ship and a board? Then, if more and more boards are replaced, until finally everything is replaced, would you have a completely different ship and a pile of meaningless garbage? Then, if after the owner came and picked up the ship, someone decided to take the pile of wood and build a replica of the original ship out of it, would at that exact moment the original ship be sitting before you? Or a replica of the original ship? What if it was all put back together again, except for one board? I guess what I'm trying to ask it....if the old parts is what makes up the original ship, at what point is the transition made?

Quote:

If it has changed it is different.

Does this mean we are not the same person we were when we were born? With our cells constantly dying and being replaced, our original bodies are long gone.

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@Theaetetus,

Theaetetus wrote:

They both are. By calling both ships Theseus that means they are both ships named Theseus. This is much like having two different humans named John. The name is only a tool for identification.

They both are, but that is not because they are both called "Theseus". That evades the issue.The issue is whether the repaired ship is still the Theseus. And the answer is yes. That is because the ship after the repair is continuous in space and time with the ship before it was repaired.

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@sthack99,

Quote:

The problem is that people are not simple material objects.

No, we aren't, but the fascinating thing is that we ascribe human identity with visual perception, much like we ascribe identity to a bike or ship. If you look at your friend, you aren't seeing his *consciousness* or *personality*, you're seeing his biological host. This is what you attach his social identity to. His face, his body, his mannerisms, many things that are anatomical/biological and are visualized.

Quote:

Sure, they may be the same old parts, but it is a new ship built with the old parts.

If you had sentimental value for the old ship, and thereby the old parts, you would better understand the identity crisis here. What's the difference between the ship and our biological bodies in terms of identity? Some do apply an intense sentimental value to materialization. Even if you don't, I hope you can see that some do.

Quote:

I do not agree that looking at the identity of material objects forces introspection or a critical look into who we are

If we are simply socially constructed and ascribed identities, much understood from visual perception, there is introspection to be had. Who are we really? Are we our bodies? If we're not our bodies, are we our consciousness? Have you lost parts of yourself you have forgotten? Would amnesia erase your identity? If you care to do so, there is much critical thought.

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@sthack99,

Sorry guys for my lack of understanding in this thread. My lack of attachment to physical objects is the cause--thanks Zetherin. There are two items that I am attached to, my acoustic guitar and my computer. But it is their function rather than the actual object themselves I value. Now if someone replaced them with broken versions I wouldn't be happy, but that is because the objects no longer serve their purpose.

I actually suffered a pretty severe head injury about five years ago, so I know what it is like to wake up and not be the same person as the day before, and understand what how it feels to lose part of myself. To others I still am that same person, but to me I am very different.

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@Theaetetus,

Theaetetus wrote:

I actually suffered a pretty severe head injury about five years ago, so I know what it is like to wake up and not be the same person as the day before. To others I still am that same person, but to me I am very different.

Wow.... That must be a terrible feeling. I'm sorry.... Sad

I kinda "lost" my step sister in the same fashion. She was in a car accident many years ago and afterwards developed severe bipolar schizophrenia (it was probably always there lying dormant, but no one knew). She's still alive, but everything about her personality has completely changed, so I can't help but feel like the person I knew and loved is gone.

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@sthack99,

Identity is largely a function of our interest in labeling such and such. If you're really attached to the old parts for whatever reason, the ship with all the old parts will be the real Theseus. If your interest is more conventional, the gradually replaced one is since we, by convention, call a thing the same if we gradually repaird it part for part. This doesn't strike me as a paradox but rather a confusion regarding labeling conventions.

Does the owner have the right to both ships? Well, that depends on what the agreement was with the mechanic. Was it agreed that the mechanic could do whatever he wished with the old parts (including keeping them)? If so, the mechanic has the right to the ship with all the old parts.

You may or may not have a paradox if you were talking about a person instead. You'll have to present the case first. I cannot imagine a person being "gradually repaired" and another "identical" person being created. What, could you chop someone's head off because it's "broken" and put it on another body? If so, what in the world does that involve?

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@Zetherin,

Zetherin wrote:

This question is not meaningless in the least. It invokes introspection, a critical look into who we are. That's far from meaningless, in my opinion.

It is useful that it forces us to think, but it is meaningless in that it doesn't refer to anything.

The question is posed as if there is something intrinsic to the vessels that would cause one or the other to be identifiable, but identity is generated on the observers end.

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