Thread: Theseus' Paradox (Philosophy fun!)

I thought I'd throw a little Philosophy into the mix.. so here's one of my favorite questions. (I don't really consider this to be a paradox, but many do.)

So the story goes that the hero Theseus rode his ship in ancient Greece to slay a Minotaur who had been demanding sacrificial victims every year for generations. Years after the Minotaur was slain and Theseus was dead and gone, the people of Athens placed his ship in their city square and preserved it for many years to come.
However, wood wears and rots and decays with time. Whenever a piece of the ship became to weathered, another piece of wood was brought in to replace it. After a while, all of the wood had been replaced. Conflict then arose:
Is the ship that stands in the square still the same ship after all the wood has been replaced? If not... then at what point did it become a second ship?
Further... what then is the pile of wood that made up the original ship? And what happens if someone rebuilds a ship of that wood? Which ship is the original ship?

There is no right answer to this question. It is completely up for debate. Feel free to put forth another situation in which the ship may have become another ship (for instance, some suggest that if a thing is the sum of exactly all its parts... the ship becomes a new ship every time the tiniest chip of wood breaks off or splinters in the wind, in which case the ship might have become a new ship thousands of times before Theseus even came back from his trip.)

Extra credit points:
Think about your answer, and then how it would relate to the same problem if the ship were instead a human. Imagine that we have this dilemma in the future when human body parts are easily replaced by mechanical or bionic parts. At what point does a person cease to be the same person?

Philosophers, on your marks...

GO!

So you think the moment of transition is when the amount of new parts has become more than 50%? And then... the ship has become, say, a monument to Theseus' ship? And what has happened to the original ship? does it cease to exist?

What is the identity of the wood which has been removed? Or the original wood that still remains a part of the ship? Is the ship 50% Theseus' ship and 50% not Theseus' ship? Or is it all a part of a new ship now?

By this token... what becomes of our bodies when, during the course of approximately 8 years, every single one of our cells has been replaced? Do we still occupy the same body?

In this scenario, however, the materials have not disappeared (nothing in the universe disappears, technically) they have simply become a pile of wood. and what if someone rebuilds this wood into a ship, using only the least amount of additional parts to be able to bring it back together?

I'd say its always the same ship, even if little bits of wood get changed. Over time, the new bits of wood just become part of the original ship, and the old wood that has been replaced is just that, old wood. Saying that anytime a chip of wood comes off makes it a new boat is wrong aswell in my opinion, if we use the human analogy that you offered, then every time a hair falls from our body we become a new human being aswell?

I think that Theseus' ship remains the same ship as long as it has more than 50% of its original material. Granted... Theseus might have replaced some of that material during the time of its ownership so that offers another variable. I think that as long as the ship is being used and owned by Theseus, whatever material it includes is its original material. Once it is out of use and is being displayed, it maintains its identity until more than 50% of the material has been replaced. The ship no longer exists in and of itself. The next challenge is to determine which of the remaining objects most holds the identity of the ship. Between the replica ship in the square and the pile of original wood, I'd say the pile of original wood. It is what theseus actually walked on, it is the only remaining true material of theseus' ship. It made the famous trip and for me, that makes it more theseus ship than a model that has been slowly reconstructed in the same place and shape as the original ship. If, however, you were to build a ship out of that material, it would not be the same ship. It would be a new ship made out of the material of Theseus' ship. I think... I'm not 100% on that... but that's my gut instinct.
It seems to me that you can determine the legitimacy of its identity by considering whether the majority of its parts are still original and if it still has the same history. A new ship built from the same material has never sailed with theseus on it and so... I don't think it is the same ship.
I also think this accounts for the human analogy. I person my replace every single one of their body parts with new pieces but as long as they maintain the same personality, thought processes, and memory of their history, they are the same person.

But this excludes the brain. If someone were to replace all of his parts, including the brain... i don't see how that person could maintain his personality or identity. If he did, would the thought processes be artificial? What would become of the memories? There would be nothing human left...

what then... does this say about the concept of a soul? Has that person died and now this is an android replica? Probably.

Originally Posted by EvilChuck

I'd say its always the same ship, even if little bits of wood get changed. Over time, the new bits of wood just become part of the original ship, and the old wood that has been replaced is just that, old wood. Saying that anytime a chip of wood comes off makes it a new boat is wrong aswell in my opinion, if we use the human analogy that you offered, then every time a hair falls from our body we become a new human being aswell?

There's two scenarios here and you have to distinguish between them.

Some would say that if one of your hairs fall out, you are not the same as before. That is an extreme view but I can understand it. I mean... technically you are not the same as before. But i think identity has to do with a lot more than just material. It has to do with history. Even if your hair falls out... you still maintain the same relationship to your history and most of your body has been through that history with you.
That is the second scenario you responded to.

But for the first one you say "even if little bits of wood get changed." That sounds a lot like an example of what I stated above, but I think you're in fact referring to the process of eventually replacing ALL of the wood. Do you maintain that the ship remains the same even when all of the wood has been replaced because it is incorporated into the identity of the ship? This is a very popular view.

However, if I take into account what I said before about history, then what happens when all of the wood has been replaced and completely lacks the historical importance the original wood had? Theseus never walked upon any of that wood... it has never even been on the ocean. Is it the same ship?

Whereas the wood that has been removed and was a part of the journey theseus made is now simply wood, to be thrown on the fire?

I'm really glad I got examples of people with the two main opposing opinions

Originally Posted by UrTimesSlipsAway

Why is this a paradox? Can you solve it?
There is a village where the barber shaves all those and only those who do not shave themselves. Who shaves the barber?

I love this paradox

There is no apparent solution to the Theseus "paradox." That is not to say that it is not possible that there will be a solution. I don't consider it a paradox because it isn't contradictory by the nature of the language (such as your paradox) and it isn't something which obviously exists but seems impossible (such as Xeno's paradox of motion). It is considered a paradox because there is no clear answer to what constitutes the identity of something, but I don't consider it to be a paradox in its purest form (which I mentioned in the original post). It is a paradox of concept... like virtue. It is merely the representation of a concept which everyone seems to understand yet no one can clearly define and so this kind of riddle arises.

Originally Posted by ImmortalDiotima

There's two scenarios here and you have to distinguish between them.

Some would say that if one of your hairs fall out, you are not the same as before. That is an extreme view but I can understand it. I mean... technically you are not the same as before. But i think identity has to do with a lot more than just material. It has to do with history. Even if your hair falls out... you still maintain the same relationship to your history and most of your body has been through that history with you.
That is the second scenario you responded to.

But for the first one you say "even if little bits of wood get changed." That sounds a lot like an example of what I stated above, but I think you're in fact referring to the process of eventually replacing ALL of the wood. Do you maintain that the ship remains the same even when all of the wood has been replaced because it is incorporated into the identity of the ship? This is a very popular view.

However, if I take into account what I said before about history, then what happens when all of the wood has been replaced and completely lacks the historical importance the original wood had? Theseus never walked upon any of that wood... it has never even been on the ocean. Is it the same ship?

Whereas the wood that has been removed and was a part of the journey theseus made is now simply wood, to be thrown on the fire?

I'm really glad I got examples of people with the two main opposing opinions

I think there are two parts to anything like this. A saying I have heard used before, and I may be quoting it wrong here but its the basic principle I want to convey; 'You die twice in life. Once when you cease to live, and again when the last person to have known you dies and with them goes your memory'. This is the same principle I feel. In terms of raw materials (life) the ship is dead, but as long as people are remembering the significance of the ship it will live on regardless of what materials have been replaced. As long as those memories are associated with that ship, even with its new bits of wood, then it remains as Theseus' ship.