A Simple Answer to the Ship of Theseus

tomatohorse

Hi everyone,

I would like to put forward a statement on Identity, along with a corresponding answer to the Ship of Theseus question, and get your feedback on it.

Identity: an object’s identity is simply that which is most useful to think of it as being. The atoms - the physical "stuff" that make up the object - exist in the Universe and follow the laws of physics. But there is no spiritual / essential / platonic / universal identity beyond that which is intrinsic to the object. Identity is an observer-generated thing, and is subject to that observer's mental framework and goals. We organisms use our concepts of identity to model, understand, and navigate our world.

* * *

Now, applying this to the Ship of Theseus, the answer to the question of, "Is it the same ship even after all the component parts have been swapped out?" is "Well, it depends -- who are you asking?"

Let’s imagine that Theseus sails into port one day and asks for his ship to be repaired. He goes into town for some R&R, and the repair crew sets to work. They start by replacing one board, then another, and another, until eventually they end up replacing every single part of the ship.

1) To the repairmen, they are thinking of the makeup and reliability of each small part and piece, and all the work they did swapping out all the components. So if you ask them, they will say, “That there's a completely different ship now, compared to the one we started working on.”

2) To Theseus himself, he doesn't care about wood density or metal alloys or any of that detail-y stuff the repairmen fretted about. No, see Theseus, he's an idea-man. Thinks big. His mind is on all the grand adventures he and his crew will have. The ship is just a vessel that gets him from point A to B across the water. Can it still do that after the repairs? Yes? OK, same ship.

3) Extending the story for fun and further illustration - let's imagine Theseus has taken out an insurance policy on his ship. His monthly premiums and deductible depend on how expensive the insurance company believes his ship to be, and how likely they think it is to fail at any point. By swapping out a certain % of his ship, the "bean counters" now see it as a higher value object and need to rewrite his policy with a new quote. They send out an assessor who, for insurance purposes, sees it as a new and different ship, and writes a more expensive policy for it. (For his shrewd business-sense, he is promptly promoted to deputy regional manager upon his return to the office).

4) Finally, let's imagine that this port town gets lots of ships coming in and out every day, and has limited dock space. So they hired a dock manager. He's a grizzled, old, salty, sea-dog sort of a fella. You gotta pay him to park your boat, and get his sign-off before you leave. You ask him if it's the same ship. “Look here, son, I gotta keep track of a hundred ships coming and going at any given time… this Theseus sailed in a few days ago, docked at ... [inaudible mumbling while checking notes]... spot #72. Now he's gonna sail out again and open up a spot for the next ship." For his purposes the ship is just "a thing that occupies one of my dock spots.” He tells you, "I ain't got time for this nonsense, it's the same damn ship, now go bother someone else with your silly questions.”

* * *

So there you have it. “Is the Ship of Theseus the same ship before and after its repairs?” To the repair crew, no. To Theseus, yes. To the insurance company, no. To the dock monitor, yes. Because an object’s identity is simply that which is most useful to think of it as being.

Most of the time ideas about identity end up being functionally very similar between people, due to shared objective reality and common experience. But differences show up when you dig deep enough, or move far enough out to edge cases (like a ship’s parts being entirely replaced).

T Clark

Identity: an object’s identity is simply that which is most useful to think of it as being. The atoms - the physical "stuff" that make up the object - exist in the Universe and follow the laws of physics. But there is no spiritual / essential / platonic / universal identity beyond that which is intrinsic to the object. Identity is an observer-generated thing, and is subject to that observer's mental framework and goals. We organisms use our concepts of identity to model, understand, and navigate our world. — tomatohorse

I like this formulation, although I wonder if you and I see it the same way. To me this says that reality as we experience it - objects, relationships, and processes in time and space - is a human construct.

And welcome to the forum.

punos

↪tomatohorse

What if repairmen came to the ship and gradually replaced every single part, but instead of throwing the old parts away they would reassemble the old ship right next to the first one with the old removed parts.

Now..
Are there two ships or one?
Are both ships the same ship?

When constructing a ship for the first time; at what point can one call it a ship or at what point does it acquire identity?
Is it a ship when its 1 percent complete? or what about when it's 50 percent complete, etc..?
Would the answer be different if it were the reverse? In other words, is the acquisition of identity from no identity the same as losing identity from full identity?

tomatohorse

↪T Clark

Thanks for the welcome! Although truth be told, I actually joined some time ago and made a few posts then...but I haven't been active at all since then, so we can pretend I'm brand new :)

I would agree with your statement, but would be sure to emphasize the "as we experience it" part of "reality as we experience it." (In other words, still recognizing an objective reality outside ourselves... but having a strong appreciation for the subjective way in which we experience that reality). It's Kant's noumena / phenomena distinction.

Gregory

↪tomatohorse

I think this question is empirical and there is a level of cohesion to atoms that form them into objects. We just don't know what that level is

T Clark

I would agree with your statement, but would be sure to emphasize the "as we experience it" part of "reality as we experience it." (In other words, still recognizing an objective reality outside ourselves... but having a strong appreciation for the subjective way in which we experience that reality). It's Kant's noumena / phenomena distinction. — tomatohorse

For me, saying I recognize objective reality and then referencing noumena/phenomena distinction in support would be contradictory. I think Kant would agree with me that there can be no reality without the human mind. Actually, I have no idea whether or not Kant would agree with me. Let's be honest, it's unlikely Kant would agree with me.

tomatohorse

↪punos

Good follow-up questions!

I would say...
There are 2 ships.
They are different ships.
I don't think many would disagree with those two answers, although if you want we can discuss those further.

"When constructing a ship for the first time; at what point can one call it a ship or at what point does it acquire identity?"
That's an interesting question, and gets into a different matter, which is that definitions can be "fuzzy" things. (Indeed, much of nature is actually fuzzy and analog rather than precise and digital. The electron cloud in atoms, our brains' neurons activating vs not to form thoughts, and the interesting new world of analog computers -- all these are interestingly fuzzy along similar lines).

I would also, if I may be so bold as to be this semantic, not speak of a thing "acquiring" identity. That language perspective implies (to me, at least) that identity is a property that the object itself possesses. I would, instead, talk about "when people begin thinking of it as [identity]." And, "what is the most useful point at which we can say, 'this is now a ship.'"

Looking at pure social averages, we could run an experiment where we get 100 people to observe a ship being built, and ask them to press a button at the point they would say, "this is now a ship." We'll get a scatter plot of answers, but they would probably all converge around an average area, with a few outliers. (Like an electron cloud model of an orbital ;) )

I like how you asked the question in reverse, too. And that would be another interesting experiment to run. Now they'd watch a ship getting disassembled and push the button at the point which they would say "it's no longer a ship." I'd be really interested to compare the results of the two experiments, wouldn't you?

Looking at another facet of the larger picture, let's say you're a politician who is making a law about when something becomes a ship vs not a ship. Maybe there are some legal or economic ramifications to consider. If you draw the line at point X, it hurts some important group of businesses in your country, so it is in your country's economic interest to draw the line at point X+1.

So where do you draw the line? The answer is that it depends on the specific thing being talked about, and who is doing the line-drawing, and what the purpose of the line-drawing is.

tomatohorse

↪T Clark

lol, well, don't sell yourself short, he might agree with you! I think it mostly depends on what you mean when you talk about "reality."

We can shift to more Kantian language, where the noumena is "the thing in itself," and phenomena is "the thing as it appears to me." When I say "reality," I generally mean noumena.

We can never directly know the noumena, because it must always pass through the filters of our perception. That filtered, interpreted idea or image of "the thing" is phenomena.

Noumena exist, and would exist even if no one observed them. Is that what you mean when you talk about reality?

T Clark

Noumena exist, and would exist even if no one observed them. Is that what you mean when you talk about reality? — tomatohorse

I'm not a Kant fan. I come to my understanding of noumena from the fact that I see it as an analogue to the Tao as described in the Tao Te Ching. This from the Stanford Encyclopedia's article on Chinese Metaphysics.

There is some ambiguity in saying that the ultimate origin is one. Chapter 42 of the Laozi says that “the one” (yi 一) generates two, which generates three and then the myriad things, but claims that the one itself is not ultimate. It is generated from dao. Chapter 40 says that things are born from being [you 有], but being is generated from no-being [wu 無]. This reflects one of the earliest metaphysical debates—is this unitary origin a thing? There seems to have been advocates for each side, but the view that came to dominate is given as a principle in the Zhuangzi: “what things things is not itself a thing”

So, the Tao is not a thing. It doesn't exist. As I see it, it makes sense to say that noumena don't exist either.

Benj96

↪tomatohorse

is worth pointing out that our bodies also have their parts replaced over time.

It has been calculated that after 8 years, due to breakdown and turnover, repair, there are none of the same atoms composing out body as there were at beginning of the 8 year period. The slowest to be replaced are the calcium and phosphate in our bones.

However our self identity, memories and experiences outlast that 8 year mark. Its not like we are all only ever 8 years old at any given time. There is continuity of self despite being composed of new material. We can recall times before that.

Therefore even though nothing about us is materially the same after 8 years we can assume to be the same person with continuous chronologic identity.

The ship is the same. It may have had its parts replaced. But the object, the whole ship with its holistic design, function and behaviour remains the same.

It would be a different case if the ship was redesigned during the replacment, if it had rooms added, masts or sails removed, the Hull made thicker or higher, the deck expanded or reduced in meters squared. These things would impact the whole ships performance and "feel" to sail - its hydrodynamics, its aerodynamics, its weight and ballast, the aesthetic, the function.

It's analogous to a heap of sand. If you replace one grain every second until the heap (of 100,000 grains) is fully replaced after 100,000 seconds, is it still a heap of sand with the same character, properties and behaviour? I would say yes. So we can still identify it as the same heap.

tomatohorse

↪Benj96

A slight correction to the human body fact (which is very interesting, isn't it?) is that our neurons don't get replaced. I wonder if replacing them would result in us "feeling" any different, within our own bodies? I suspect not, assuming they could be 100% perfectly replaced, in the same configuration and size and such. Because thoughts are more emergent things that appear as a "sum of the parts" of the neurons firing in their arrangements.

But other than that, yes, I think your answer fits rather well with my own.

Except, can you think of any cases where the ship would not be considered the same ship? I tried to do that with my example of the repair crew and the insurance co. Do you agree or disagree with those examples, I wonder?

unenlightened

can you think of any cases where the ship would not be considered the same ship? — tomatohorse

When the ship was discovered, it was at first thought to be the ship of Theseus, but tree-ring analysis and carbon dating unequivocally showed that it was of a later date, and a mere replica of the original.

Philosophers hate vagueness and 'it depends' answers, and that's why these questions trouble them so much. So your obviously correct analysis will irritate rather than satisfy. Well done!

Banno

↪tomatohorse

You've re-discovered Wittgenstein - the meaning of a term is the way we use it. Forget about meaning and look to use.

Well done, you!

Welcome.

Banno

To me this says that reality as we experience it - objects, relationships, and processes in time and space - is a human construct. — T Clark

Constructed from a shared world, yes.

Banno

In other words, still recognizing an objective reality outside ourselves — tomatohorse

Yep.

T Clark

Constructed from a shared world, yes. — Banno

Yes, by which I mean no.

Benj96

slight correction to the human body fact (which is very interesting, isn't it?) is that our neurons don't get replaced. I wonder if replacing them would result in us "feeling" any different, within our own bodies? I — tomatohorse

However I'm referring to atoms not neurons. Yes you're correct the neurons don't replicate, they stay as is for life, that isn't to say the atoms that make them up are not removed and replaced.

This simply means that neuronal structure is highly preserved despite repairs and replacement of its compoments.

For example, cholesterol and lipids from a neurons membrane become damaged by oxidation and get drawn into the cell for destruction and recycling. New fats and cholesterol are simultaneously transported out to the membrane to maintain continuity.

The neuron does not reproduce like other cells of the body but that isn't to say their composition is static.

The body creates structures which are subject to wear and tear. Some tissues combat this by cell division and replacement of whole units. In other tissues, the cells are not replaced, but their composition is dynamic, when it wears down individual pieces are created to take over in their place, sustaining the cell without reproduction.

Down The Rabbit Hole

↪Benj96

The ship is the same. It may have had its parts replaced. But the object, the whole ship with its holistic design, function and behaviour remains the same. — Benj96

That doesn't seem right to me. An object goes where its parts go. If the original parts were put back together, that would be The Ship of Theseus. And they can't both be The Ship of Theseus

tomatohorse

↪Benj96

Thanks for that further elucidation :) Biology is fascinating.

noAxioms

Identity: an object’s identity is simply that which is most useful to think of it as being. — tomatohorse

That's the pragmatic language answer, so I agree, at least until the assumptions upon which the pragmatic utility is based remain functionally true. Theseus has the shipyard guys 'fix' his boat, and all the parts are replaced. It's his, especially in a legal sense. The shipyard guys can build a new boat with the removed parts (or have never even bothered to disassemble it) and that's a new boat now.

Theseus has taken out an insurance policy on his ship. His monthly premiums and deductible depend on how expensive the insurance company believes his ship to be, and how likely they think it is to fail at any point. By swapping out a certain % of his ship, the "bean counters" now see it as a higher value object and need to rewrite his policy with a new quote. They send out an assessor who, for insurance purposes, sees it as a new and different ship, and writes a more expensive policy for it. — tomatohorse

Just a nit, the new policy should be cheaper, since the repaired boat is less likely to sink due to its age, and they'd need to fork out for a new boat anyway if the old beat-up one sinks. This is pretty irrelevant to the topic.

Concerning the repaired boat and the one made of the original materials:

I would say...
There are 2 ships.
They are different ships. — tomatohorse

Probably. Which is which?

Suppose we have a teleport device like on Star Trek. This is one of those things I spoke of above, something that violates the assumptions upon which the pragmatic utility is based. Spock's atoms are destroyed and new atoms are assembled into Spock elsewhere. Is it Spock, or just a copy of him? The pragmatic answer is the former. The new atoms are the same legal entity.
For the record, they actually have such a thing, but it only works on little things, not even the size of an atom. It is a true teleport: You can teleport one particle of an entangled pair and the new one at the far end is still entangled with the other particle of the pair.

Back to Spock: What if the original persists for 2 seconds after the new Spock at the destination has been created? Now there's clearly an original and (doomed) copy. Is the destination Spock now still the original? If not, what changed?

There are other interesting scenarios that similarly challenge those assumptions which happen to be reasonable in most practical situations.

However I'm referring to atoms not neurons. Yes you're correct the neurons don't replicate, they stay as is for life, that isn't to say the atoms that make them up are not removed and replaced. — Benj96

Nerve cells very much do form/replicate well after birth, but that stops at a young age. Just because new cells don't form after a while doesn't mean they retain their original atoms. They'd die if they couldn't take in new atoms (nutrients) and get rid of waste ones. Individual atoms don't hang on to their electrons even if the nuclei stick around.
At the quantum level, no particle has a real identity. There's just energy that's conserved, and there's no 'this energy' as distinct from 'that energy'.

An object goes where its parts go. — Down The Rabbit Hole

Can you justify that? If the parts are moved one at a time, at which point does the identity move? What if one nail (or whatever part you designate as the critical one) is left with the ship being fixed?

Your parts change all the time, and yet you probably consider yourself to be the same person as you were earlier. Less than a thousandth of a percent of your current material is original material, so are you somebody else now?

Down The Rabbit Hole

↪noAxioms

Can you justify that? If the parts are moved one at a time, at which point does the identity move? What if one nail (or whatever part you designate as the critical one) is left with the ship being fixed? — noAxioms

I think the best way is to say that as soon you change it, it is not the same ship. This is contrary to the common way of identifying things, and would mean there is no Ship of Theseus until all of the original parts are put back together.

I'd rather deal with any difficulties that arise from this than say that an object that has been taken apart and then put back together is not the same object.

Your parts change all the time, and yet you probably consider yourself to be the same person as you were earlier. Less than a thousandth of a percent of your current material is original material, so are you somebody else now? — noAxioms

I have always considered "me" to be my mind. When I say something like "my body", I mean the body that belongs to me.

noAxioms

I think the best way is to say that as soon you change it, it is not the same ship.
...
I have always considered "me" to be my mind. When I say something like "my body", I mean the body that belongs to me. — Down The Rabbit Hole

But there is no one body that belongs to you since it is a different one each moment by your definition. Since you have a different body every moment, why do you not jump all around the neighborhood from one moment to the next? Or would you not notice if it did? That depends of course on if memory is part of this 'mind' you posit or part of the body.

I'm asking what ties the body you've selected/inhabited in one moment to the different body you selected in the next moment, and why that 2nd body needs to be a specific one and not a random one.

Down The Rabbit Hole

↪noAxioms

But there is no one body that belongs to you since it is a different one each moment by your definition. Since you have a different body every moment, why do you not jump all around the neighborhood from one moment to the next? Or would you not notice if it did? That depends of course on if memory is part of this 'mind' you posit or part of the body.

I'm asking what ties the body you've selected/inhabited in one moment to the different body you selected in the next moment, and why that 2nd body needs to be a specific one and not a random one. — noAxioms

I would say even on a materialist approach the memories themselves are part of our mind.

And it seems okay to say that our body will not be the same, and we will thus have a different body.

A Simple Answer to the Ship of Theseus

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