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The Ship

  1. Apr 30, 2005 #1
    If every part of a ship is replaced once, is it still the same ship?
  2. jcsd
  3. Apr 30, 2005 #2


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    Yes. And the implication that the ship is something different from the sum of its parts is true too.
  4. Apr 30, 2005 #3
    How did you reason to reach that conclusion?
  5. Apr 30, 2005 #4
    This is what i think:

    Its a different ship, because the observer knows its parts were replaced (im assuming the observer knows the truth).
  6. Apr 30, 2005 #5


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    I think SA's implication provides its own explanation: because what makes it a "ship" is the arrangement of the parts, not the parts themselves. That's why the whole is greater than the sum of its parts.
  7. Apr 30, 2005 #6
    What if I were to add a part to the ship, is it still the same ship?
  8. Apr 30, 2005 #7
    what happens if it was added peice by peice?...each new peice would carry on the "spirit" of the original ship therefore causing the ship to remain the same.

    if it was put together at the same time....i guess that i would have to say no to that cuz it is like a completely different ship....strange.You would think that the arrangement would be the same for both ships if you are trying to replicate the first, so i personally dont see russ_watters example (although i do understand what he say about it being greater than the sum of its parts.)

    here is another thing though, what happens if the ship is only 1 peice??? :P
  9. Apr 30, 2005 #8

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    This is the classic Ship of Theseus paradox. Here's a few modern resolutions to the problem I found at Wikipedia:http://en.wikipedia.org/wiki/Ship_of_Theseus

    By FAA regulation, each airplane has a tail number to identify it. If the plane crashes and only the left rudder remains, the aircraft can be rebuilt and remains the same airplane. If the left rudder is then replaced, it is still the original airplane.

    ...Each automobile is identified with a unique number inscribed in various locations, and this number is associated with the vehicle's legal registration. However, any number of parts can be replaced and it will still be considered to be the same vehicle. In some cases, an antique or desirable wrecked vehicle will be "repaired" by having its identification markers transferred to a new vehicle...

    Computing / Digital rights management

    ...unlike automobiles that can have parts and still be considered the same vehicle, Microsoft's Next-Generation Secure Computing Base considers a computer with a replaced processor (and consequentially a new Fritz-chip), to be a different computer. Consequently, it will charge for a second licence on the "new" computer.
  10. May 1, 2005 #9
    the sum of the parts can never be greater or smaller than the total. because then the total, is a different total. it is the total of the sum of the parts now.
  11. May 1, 2005 #10


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    This is a logic question, not a physics question, right? Why not flesh it out with some examples:
    Say ships S and T are identical except that S is housed in bunker U and T is housed in bunker V.
    1) Replace each piece of S with the identical piece of T, and vice versa. Which ship is in bunker U?
    2) Take each piece of S to bunker V, stand there for a while, bring the piece back to bunker U, and put it back on ship S. Which ship is in bunker U?
    3) Take the masts from S and T, mix them up in a bag- don't peak ;) - now which one is the mast from S?
    Say S and T are also different colors; Would that make a difference? Why?
  12. May 1, 2005 #11
    Well, paradoxes and puzzles hunters in philosophy (and in other related disciplines) think that it isn't. Since Thomas Hobbes raised this "Ship of Theseus' puzzle it has stuck ever since, and like Frank Jackson's/Chalmer's "Hard problem" in philosophy of mind, it remained as hell-raising and hair-splitting as ever. We are stuck with all these "Knowldege Gaps" concepts. In Thomas Hobbes' account the entire ship was replaced, planks by planks, by a completely new ship. Not even a single one of the old planks or parts was left unchanged. And wait for this, according to Hobbes, all the old parts were reassembled and put back together. If this is true, in what sense then is the new ship still the same as the old? Metaphysically and epistemologically, I would say "absolutely, none!". The old ship (if it is true that it was completely put back together again) remains forever Metaphysically Enforced as its good old self. Coversely, the new ship is metaphysically equivalent to building a completely new ship. It stands forever metaphysically, semantically and epistemologically distinguished from the old!

    A HEALTHY MENTAL STATE of the perceiver is grounded and guaranteed by this metaphysical separation of the new ship form the old.


    Metaphysically, an identity is shared when the old parts of a given entity is mixed with new parts. This must be scientifically and philosophically admitted. The EPISTEMOLOGICAL STATUS (ES) of Theseus Ship is such that when new parts are mixed with old parts multiple identity is not only metaphysically enforced but also semantically and epistemologically presupossed. At this point the philosophy of language must intervene and provide clear and logically precise linguistic devices for expressing and coveying multiple identity claims in propositions from one perceiver to the next.

    In science, this has far-reaching consequeces in such areas as "Body Parts transplantation","Blood Transfusions", "Cognitive Science", "The Psychology of Multiple personality" etc. For example, does the passing of genes or cells from one living creature to the next via body parts transplantation or via blood transfusion, also passes on different personality traits to the receiver? In ethics and philosophy of action, there is the question of whether multitasking is multiply personalised, or whether one person or soul is merely sequentially queueing human actions in a decisively multitasking way. All these questions are what the Philosophy of PERSONAL IDENTITY is inevitably invoking.

    Many philosophers still believe that there is a knowledge gap immediately rising from the thesis. I personally do not see much of such problem of knowledge gap. I see it as a matter of individual epistemologies germinating or rising from individual modes of interpretation. Parafuses muddled up with paracpets!
    Save our world from destruction........Stay GREEN!
    Last edited: May 1, 2005
  13. May 1, 2005 #12


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    Not true at all. Take a pile of parts and try to sell it for the same price as a fully-assembled ship and see if you can. If nothing else, the labor required to build it is part of the cost of the ship and that is not a price that's included in the sum of the parts alone.
  14. May 1, 2005 #13
    i would definitely say the answer is "no"

    say for instance, that each new part of the ship looks exactly the same as it's old counterpart, so that once finished, the ship will look 100% identical down to the exact detail. in the end, the ship will fall under the same scope as the previous ship, in that it will look identical. it's the same as saying, two people who own 93 Honda Accords own the same car--but it's not _physically_ the same car.

    now suppose you took all of this material, but instead of replacing parts on the old ship, you made a completely new ship. so the possible scenarios are that:

    1) you have ship A, slowly transformed into ship B


    2) you have ship A, and you also have ship B

    now in both cases, the end result is exactly the same. but in the second instance, it would be absurd to suggest that ship B is ship A! given that ship B in both scenarios are exactly the same, how would you resolve that one ship is it's own, new ship (ship B), and that the other is ship A?

    i would go as far as to say that if you were replacing a ship piece by piece, that even the very first replacement piece constitutes a new ship. However, by convention, it's a lot easier for people to call it the same ship, since 99% of it is exactly the same. wouldn't it be confusing if everytime someone got their car fixed, they claimed to have a "new car"?

    to me, the problem is just that--a convention of language. all of this works under the assumption that existence relies upon an arrangement of matter; and that if you change this matter, you do not have the same thing as you did before.
  15. May 4, 2005 #14
    The human body

    Eventually in less that a year all the atoms in our bodies are replaced by different atoms. Now the question. Are you the same person as you were last year? Some may argue that no, psycholgically everyone is in a dynamic state as far the mind goes. Our bodies change concstantly physically speaking so the answer is that "no", I am not the same person as last year.
  16. May 4, 2005 #15
    oh, no.

    Don't use this logic to proof. I am saying that the sum of the parts is always eqaul to the total: and this IS TRUE no matter what you say. What you demostrated me, and in a very particular way that I find very interesting, is that the cost of the parts isn't equal to the cost of the boat.
  17. May 4, 2005 #16


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    Are you being purposely obtuse? That's exactly what is meant by the statement!

    "The whole is greater than the sum of its parts" is a very, very common saying. In this case, what it means is that the boat is worth more than the sum of its parts. Have you just not heard it before?
  18. May 4, 2005 #17
    aah, thanks.......NO. I had never heard it before.
  19. May 4, 2005 #18
    If you define "this ship" as this particular set of atoms arranged in such a manner, then it's not the same ship as soon as one is lost.
  20. May 7, 2005 #19
    hmmmm.. this is a very complex logical problem. The answer of course is no and yes.

    The boat in this question is actually a metaphor for consciousness (or say a persons brain), and the real question is what happens if consciousness (or the brain) is copied. If you are the boat then where do you end up?

    and yes the first answer is that the answer is probably indeterminate - both the first and second boats think they are the (original) boat.

    Unfortunately there is a better answer - the original boat was destroyed during the copying process.
    There are two new boats, one built from the parts of the first and the other from the new parts. Although each boat 'thinks' it is the original, it is in fact a new boat. The original consciousness is actually dead, this is because consciousness is 'indestructible' it cannot be separated into component pieces
    without disappearing forever.

    The argument gets more complex however because it may be possible to replace the brain a piece at a time as without disturbing the consciousness itself but here we are arguing directly "what is consciousness" - is it state, is it an electrical field, is it neurons, is it the physical body, is it even some kind of spirit?, some kind of quantum transience, or something else?
  21. May 7, 2005 #20
    It all arises from the sloppy attempt of human beings to shuffle objects into neat categories. It's a semantic debate, no more.
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