Tthe Ship of Theseus paradox

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In the series and book "The Three-Body Problem," the character Will Downing has terminal cancer. In order to give meaning to his final days, he agrees to have his brain cryogenically preserved so that, in 400 years, his brain might encounter aliens who could study humanity. However, midway through the journey, the ship carrying Will's brain malfunctions, leaving him adrift in space.

That being said, I have a few questions. Is he still the same person, assuming that only his brain is the original part of his body (the Ship of Theseus paradox)? For those who are spiritual or hold other religious beliefs, has he already died and will he reincarnate, or does his brain being kept in cryogenic suspension still grant him "life"?

in PhilosophyofScienceby xMoonknightx

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1mo

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Calion

1mo

That question only makes sense if you believe that, when all parts have been replaced, it's not the same ship. The core question is: Once every part, every nail, every board has been replaced, is it the same ship?

Subsidiary questions don't make sense until that one is answered.

fullPlaid

1mo

okay i was trying to be informal about this but i got down voted for nicely asking for clarification and if you wanna say it doesnt make sense then im gonna have to try.

consider a set of objects. if you remove one object, the new set is by definition no longer the original set. if you add a new different object to replace the removed object, the newer set is also not the original set.

it is a stronger assertion that a set is no longer the same if a single object is changed than the assertion that a set is no longer the same if all the objects are changed.

the reason single object replacement is strong and all object replacement is weak is because the former proves the latter and everything in between.

so it does make sense to ask the question about single object replacement.

Calion

17d

I feel like this is begging the question. The very question is, "at what point, if any, does it become not the same ship?" You're defining the question such that the answer is "if even one nail is replaced, it's not the same ship." While that's certainly a valid answer, it doesn't match basically anyone's intuitions.

fullPlaid

17d

the question can be answered from a more generalized perspective. essentially, the question is a special instance of the more general question of when a ship is no longer the same after one or more parts is replaced -- which logically includes the replacement of all parts.

this is a common strategy in logic, especially rigorous logic such as mathematical proofs. recent example being the proof of the Poincare conjecture:

https://en.m.wikipedia.org/wiki/Millennium_Prize_Problems

A proof of this conjecture, together with the more powerful geometrization conjecture, was given by Grigori Perelman in 2002 and 2003.

another example being, Fermat's Last Theorem was proven by a more generalized problem:

https://en.wikipedia.org/wiki/Wiles%27s_proof_of_Fermat%27s_Last_Theorem

Wiles's path to proving Fermat's Last Theorem, by way of proving the modularity theorem for the special case of semistable elliptic curves, established powerful modularity lifting techniques and opened up entire new approaches to numerous other problems.

btw, in my view the literal question is fundamentally flawed -- regarding replacement of parts, not a literal ship. is a tree still the same tree after its grown? its assuming that the definition of an object is a fixed moment of time in three dimensional space. as soon as you include a fourth dimension, the question and answer becomes more clear. also the levels of four dimensional similarity can be used to describe to what degree a ship is the same, or any two objects for that matter.

but i think i dont understand what youre claiming. what do you believe people think the question is asking?

Calion

17d

My point is that, with the "set" framework, you are defining the question to have only one answer: The ship becomes no longer the ship when any part of it is lost or replaced. That defies the point of the question, which is that most people have the sense that that is not the case, but also that there's no definitive point at which it becomes "not the same ship," but also that it's odd to call it the same ship even after all its parts have been replaced. The point is to explore that intuitive paradox.

That doesn't mean that it's unanswerable, and it doesn't mean that "if even one piece is missing, it's no longer the same ship" is not a valid answer—but is that really how you view it? Is that how you look at yourself, for instance? "I lost a skin cell, therefore I'm no longer the same person!"

fullPlaid

17d

my point regarding the set framework was not that it is the correct answer (although within its assumptions it is correct). my point was that because it answers a more general question, that generalized question is reasonably well connected to the original paradox, which counters the original comment to OP stating:

This is very much not the Ship of Theseus

so im basically saying it kind of is in the sense that its a general form of the Ship of Theseus. i was questioning the "very much not" and then it somehow turned into a divisive discussion lol

and no, as i explained in my previous response, i think the Ship of Theseus is an ill-posed question. i said it would be more accurate to define something in four dimensional space. but i guess it kinda just passes the buck. maybe its even more accurate to define something in the dimensions it exists (3 space, 1 time) and compare things based on a spectrum of similarity, instead of using binary -- the same or not the same.

how do you go about answering the question?

Calion

17d

I can see how your set framework is related to the Ship of Theseus question, but it isn’t the same question, so “very much not” might have been something of an exaggeration, but is still basically true. You could have said something like “I know this isn’t technically Ship of Theseus, but here’s a related problem that you could consider Ship of Theseus to fall into which may shed some light on the subject.”

I definitely don’t think Ship of Theseus is an ill-posed question, as it gets right to the heart of a seeming contradiction in our intuitions. That’s great! That’s what philosophy should do!

The actual answer, however, it pretty boring. It boils down, as very many things in philosophy do, to definitions. Just what is your (not you your, whoever is being posed the question) definition of “ship” (and probably “same,” I guess)? Oh, you don’t have one? Well, that’s the problem then. If you had a cogent definition of “ship,” you’d very quickly know your answer to the puzzle.