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Theseus' Ship Paradox

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Trigger: This ol' broom... has had 17 heads and 14 new handles in its time.
Sid: How the 'ell can it be the same bloody broom, then?
Trigger: Well, 'ere's a picture of it; what more proof do you need?

The Ship of Theseus is a classic philosophical thought experiment about the nature of identity. Is an object simply the sum of the specific parts that compose it? And if those parts are gradually replaced, is it still the same object?

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The classic story goes as follows: Theseus sails the world on his famous ship, but as the pieces of the ship begin to wear down, he replaces them. By the time his voyage is finished, every single part of the ship has been replaced. So is the ship at voyage's end still the same ship that first set sail? If yes, what would have to have to happen for the ship to stop being considered the original? If no, at what point did the ship stop being the original?

Another version holds that, after sailing the world on his ship, Theseus docks it and keeps it in working order by gradually replacing all of its pieces. Someone else buys all the pieces that Theseus discards and assembles a second ship from them. So which is the ship that sailed the world? The one in Theseus's dock, or the one built of all the pieces of the original ship?

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Or for a more concise example, if you have a hammer and the head breaks, you replace it. But if later on the handle breaks, you'd have to replace that as well. But would it be the same hammer anymore?

Due to the above exchange on Only Fools and Horses, British tropers may be more familiar with referring to this dilemma as the "Trigger's Broom Paradox".

Examples of the conundrum in fiction can play out with virtually any object. A common alternative to this is the "Grandfather's Axe" story. The trope gets a lot of play in science fiction when we consider whether Cybernetics Eat Your Soul. If you replace parts of your body with machines, are you still really you?

Compare with Soulless Shell.


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Examples

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    Advertising 
  • An old toothpaste commercial shows a futuristic apartment with a guy who claims that his grandmother still uses the same toothpaste and that her teeth are the only parts of her that are original. Cue a stunning young blonde passing him with the guy giving her a "Hey, Grandma!" The ad was shown at a Russian game show, and the team was asked to figure out what was unlikely about it. Naturally, they focused on this trope, arguing that it's impossible that a person could have nothing original except her teeth. The real answer was that the tooth shown in the ad had four roots, which is extremely unlikely (many viewers agree that the team should've been given that point).

    Anime and Manga 
  • This effectively gets used in one early arc in Ah! My Goddess when the Nekomi motor club is in a series of races involving 49cc Honda Supercubs. Each race has a different level of customization allowed. Keichii gets the "funnybike" category, which basically means that anything goes in customization so long as at least one part from the original bike remains. Which means that Keichii ends up riding a 1300cc monstrosity which happens to have the handlebars and brake pads of a Honda Supercub.
  • In Battle Angel Alita characters such as Alita frequently replace their entire bodies with robot ones, with their still-organic brains being the only still-human part of them. Alita eventually finds out that after getting blown up by Desty Nova and reconstructed in-between the original manga and Last Order, her brain was replaced with a Tipharian brain chip with her memories uploaded into it, leaving absolutely nothing left of her original physical being, and the resulting identity crisis causes her to literally disintegrate. Don't worry, she gets better.
    • The revelation that Tipharians' brains are replaced with brain chips without their knowledge, meaning that while they still have their original bodies they are effectively copies of their original selves is a huge shock to these characters, one of which actually saws his head open with a circular saw to check and then Goes Mad from the Revelation shortly before being executed, while another ends up jumping to his death.
  • In the Alternate History of Code Geass, the British Empire kept and expanded upon their colonies in the Americas, then lost the British Isles themselves to Napoleon's invasion. Since the royal family that escaped to the American colonies couldn't accurately call themselves "British" anymore, and apparently didn't consider themselves "Americans" either, they called their territories from then on "the Holy Britannian Empire".
  • A recurring theme in the Ghost in the Shell franchise, where characters can replace every single bit of their organic body with mechanical prostheses, including uploading themselves to a cyberbrain. The term "Ghost" is used to refer to an intangible essence (akin to a soul) that makes such full-body cyborgs human instead of just highly-advanced robots with human memories.
  • In Land of the Lustrous, the Lustrous are people made of gems, so if parts of their body are broken off, they can receive new material to replace those parts. Phosphophyllite, however, is an exception, because they is a rare type of gem, so it is very important that they avoid fracturing as much as possible due to their extreme fragility. On the other hand, Phos' body is compatible with using the body parts of other gems. Over the course of the series, Phos has lost their legs and had them replaced by agates, had their arms replaced by a gold & platinum alloy, body replaced by crystals, their head replaced by the head of a whole gem, Lapis Lazuli, and left eye replaced by a pearl. Rutile discusses this trope by the time they replace Phos's head, since half of Phos's body is by that point from other gems, wondering if they can even be called "Phosphophyllite" anymore.
  • This gets addressed in One Piece when the Straw Hats are hoping to repair their ship, the Going Merry. Because the keel (essentially the backbone of any ship) is severely cracked, the ship is declared irreparable. When Luffy suggests they just build a "new Going Merry", it's pointed out that even if the shipwrights built a new ship precisely like the present Going Merry and built to the Merry's specifications, it actually wouldn't end up being precisely the same, because of inevitable variations in the construction material. It wouldn't be the same ship and the crew would definitely feel that it wasn't the same ship, even if it was built the exact same way, making it pointless to build the same ship from scratch rather than just building or buying a new one.

    Comedy 
  • In the Stanley Holloway monologue The Beefeater when visiting the Tower of London they are told that the axe on display "has 'ad a new handle, and perhaps a new 'ead, but it's the old, original axe".

    Comic Books 
  • In a 2017 issue of The Avengers, the Vision has a conversation with a future version of himself who apparently lasted until the end of time. When present-Vision is disturbed at the notion that he'll outlive all his friends, future-Vision cites Theseus' Paradox to question if they're technically the same person.
    Vision: I grant your query, but regardless of how many of my—your—artificial limbs and organs may have been exchanged, your intangibles—your brain patterns—will forever remain based on an ex-Avenger named Simon Williams.
    Future-Vision: ...
    Vision: Won't they?
  • Guardians of the Galaxy (2020): Discussed between Drax and his daughter Moondragon in issue 3, regarding Drax, who thanks to various shenanigans, deaths, resurrections and messes with the Soul Stone is unsure whether he's really the same Drax or Arthur Douglas, and is unsure whether he owes anything to them.
  • In The Manhattan Projects, as his injures start piling up, Von Braun has replace more and more of his body with primitive cybernetics. He begins to privately wonder how long it will be before he’s all machine, and if he’ll still qualify as the same person afterwards.
  • The Ultimates (2015): During a chat between the newly redefined Galactus and the Molecule Man, the latter brings up the recent destruction and rebirth of the multiverse. Owen asks whether, given that so many and so much transitioned through, whether the old omniverse ever died at all, and what that means (especially in regards to Galactus' role in all of it.)
    That omniverse died. But a lot of the lives in it carried on to the new one. Same broom—new handle. So. Did the omniverse die? Are we the eighth cosmos, or still the seventh?

    Fan Works 
  • The Cutie Mark Crusaders Bring About The Apocalypse: A revived Discord switches the Mane 6's bodies around, and then causes their memories and personalities to be slowly replaced by those of the pony whose body they now inhabit. Discord then further messes with them by explaining this trope to them, causing them to wonder if the original Mane 6 will still truly exist once they completely switch.
  • Eugenesis: Towards the end, Nightbeat dies, but leaves behind a device and blueprint that will allow the others to rebuild him. Afterwards, he reflects on this trope; he’s exactly like he was down to the very second that he died, but he’s been built from the ground up and doesn’t have one bit of his original body in him. So does that make him a clone rather the original Nightbeat?
  • In Forged Destiny, Jaune creates Crocea Mors to the exact same specifications each time he crafts it. The original steel sword was shattered in the battle with Watts but Jaune gathered some of the shards and reforged the blade using Vacuan Silver. Jaune perfectly recreates the blade again when he gets hold of some enchanted metal. When that blade is similarly broken, he makes a new sword from scratch but still with the same shape, weight, balance, and reach as each of the previous ones. Each of these swords is still Crocea Mors according to Jaune's second Passive, Blade Bond, which increases damage dealt in proportion to the length of time the same sword has been wielded.

    Film — Animated 
  • In Ron's Gone Wrong, the titular robot suffers various programming glitches that cause it to develop its own personality from interacting with its owner, Barney, rather than just being a means of expressing Barney's social media interests. When CEO Marc Weidell "fixes" Ron, Barney makes it clear that this bot might be physically Ron, but he wants the original Ron's personality back.
  • Waking Life has one segment with two women taking about being in their fifties, and that how people have to make up stories about who they were when they were younger. As noted in the Real Life segment, the human body is constantly regenerating cells, so they're both completely new people several times over since they were infants.
  • In WALL•E, it's implied that the titular robot had at one point or another replaced every part of his body from one of the robot spares he keeps in his house, except his motherboard. So, by the end, when Eve replaces his motherboard after it gets severely damaged, Wall-E acts like any other garbage disposal robot until Eve kisses him.

    Film — Live-Action 
  • In A Christmas Story, Ralphie notes that the Old Man's tires were only tires in the academic sense. "They were round, and at one point were made of rubber."
  • John Dies at the End: The film opens with David beheading a body with an axe. However, the handle breaks and he gets the handle replaced. Later, he chips the head killing a centipede... thing. Eventually, the guy he beheaded comes Back from the Dead, and the reanimated corpse points to the axe and says, "That's the axe that slayed me," to which David asks the audience, "Is he right?" The plot point from the original book that this question foreshadows was removed from the film.
  • The World's End: The Beast has had every meaningful part replaced, but looks the same and runs about as junkily as it did in the '90s. This foreshadows what the Network has done to Newton Haven: it claimed the place was "better" and only killed and replaced who it needed to, but over the last two decades only three of its human residents remained and most of the local culture has been erased. All this leads to Gary, Andy, and Steven asking the Network how it can consider it the same town.
  • Avengers: Age of Ultron: Before the third act, Tony and Bruce download JARVIS into a vibranium synthezoid body that Ultron intended to use as his ultimate form, and Thor brings him to life with lightning from Mjolnir. The result is a being they take to calling "Vision". Vision has the physical form of the actor who voiced JARVIS, and is primarily composed of JARVIS's matrices, but he insists he's not JARVIS. Ultimately, Avengers: Infinity War establishes that he's comprised of the minds of Tony, Bruce, Ultron, JARVIS, and the Mind Stone.

    Folklore 
  • The "axe" version is the basis of an urban legend; a museum visitor is shown the axe used to behead Mary Queen of Scots (or the axe George Washington used to cut down the cherry tree, or any other historically significant axe), and their guide adds that it has had three new heads and two new handles since then.

    Literature 
  • Alcatraz vs. The Scrivener's Bones: Discusses this trope.
    Alcatraz: I used to be a young, idealistic hero. But like the ship of Theseus, that person has been changed so many times it no longer exists. If it ever did in the first place.
  • In Armageddon III: The Remake by Robert Rankin, the 25th century Private Detective Lazlo Woodbine describes his standard issue fedora thusly:
    Same hat my ancient ancestor wore back when he was a private eye in the nineteen-fifties. Sure it's had thirty new brims, eighty new bands and more crowns than the House of Hapsburg since then, but it's the same hat. Same old hat, same old joke. Class never dates, see?
  • The Belgariad. Alluded to in the Malloreon series. Poledra tells Beldin that she's surprised he hasn't changed his tunic during the thousands of years since she last saw him. Beldin says that he patches it, and replaces the patches as they wear out, to the point that the original tunic "is only a memory".
  • Towards the end of Bicentennial Man, Andrew Martin starts a Frivolous Lawsuit over how much of a human can be replaced with robot-like parts before they're no longer human to get a precedent on the opposite - how much of himself he needs to replace with human-like parts to be considered human. The ruling ultimately decrees that the one part that matters is the one thing he can't swap out - his brain.
  • Card Force Infection: Fletcher has used "the same" deck since he first got into Card Force shortly after his parents divorced, though numerous little changes over the years mean that it doesn't actually have any of the same cards it had then. Losing it to Maxwell is directly compared to "sinking the Ship of Theseus".
  • The Cosmere: All things—including objects—have a physical, cognitive, and spiritual element. The cognitive element involves how the object is viewed, and how it views itself. A ship is just a few awkward pieces of wood, except people think of it as a ship, so eventually it begins thinking of itself as a ship as well. This provides a solution to the paradox: As long as the repairs and replacements are done slowly enough that people still think of the ship as the same ship, the ship itself will agree.
  • The Fifth Elephant
    • Brought up several times, generally in regards to a Dwarfish axe which has been passed down through the family for generations: sometimes the head needed replacing, other times the shaft, still more times the eye or the bit, but it's still the same ancestral axe, and it works all the better for having changed when it needed to.
    • Played to the hilt in the book's climax, where no one's terribly upset that the conspiracy to influence the Dwarfish succession involved destroying the Scone of Stone and replacing it with a perfect replica: the Scone had already been replaced many times over the centuries, but it had always remained "the thing and the whole of the thing."
    • Another Discworld novel discusses the example of a witch's broom that is malfunctioning. No matter what part of the broom got replaced—and eventually, all parts of the broom have been replaced at least once—the malfunction stubbornly refused to disappear.
    • In The Shepherd's Crown, dwarfish craftsmen finally get the chance to do a proper repair job on Granny Weatherwax's broom. This essentially involves building an entirely new stick around the idea of Granny Weatherwax's broom. It gets compared to the axe above in a footnote.
  • Honor Harrington mentions that a particular chair has been in the Protector's Palace nursery for over seven hundred years, plus or minus the odd frame repair or reupholstering.
  • John Dies at the End: The book begins with exploring this question. David beheads a body, but the handle breaks on the last swing. He replaces it. He later chips the head on another supernatural creature, and replaces it. When the guy he beheaded comes Back from the Dead, the reanimated corpse points to the axe and says, "That's the same axe that beheaded me," to which David asks the reader "is he right?" This question foreshadows the question of whether "monster Dave" can be considered the same person as the original human Dave that he unwittingly replaced.
  • Questioned in The Last King. The narrator wonders whether, after replacing each and every part of his grandfather's axe, it is still the same axe.
  • The English Little Red Engine picture book series about a sentient locomotive includes a title The Little Red Engine Goes to be Mended. In it, a trip to India leaves the Little Red Engine covered in rust after being left outside during the rainy season. It is taken to be repaired, but is found to be in such a bad state as to make it necessary to completely strip her down. While waiting to be taken apart, another engine tells the Little Red Engine: "As long as they still have a drawing of you with your number and your name you’ll be all right. In the drawing you are seen as a whole. The whole is more important than the parts, so it does not matter if they take away the bits. And your name and your number tell people who you are. While they still have those you retain your identity - you are still the Little Red Engine - you are still yourself." The engine is then taken completely apart and the parts taken away. We are told explicitly that one original part of the engine - its name and number, has been taken for restoration. Also, when Sam Trigger, its driver, comes to the shop to see how things are progressing, he is told that some unnamed smaller parts are in a water and caustic and soda bath to remove the rust and oil; these will be reused if they are not too badly damaged, in which case they will be sent for scrap. Sam then sees some major parts being built more or less from scratch.note  Then all the engine's parts are brought together and reassembled; the Little Red Engine, now shown as sentient again, is repainted. Sam gets her going, and drives her home. The book presents something of a mindscrew; whether any substantial portion of the original components have been re-used, or whether all but perhaps a symbolic handful of parts of the Little Red Engine were built anew, is an open question. Judge for yourself here.
  • Oz stories
    • An early example is the Tin Woodman from The Wonderful Wizard of Oz. He pissed off a witch who enchanted his ax so that it would cut off pieces of him, and he went to a tinsmith to replace the missing parts. Eventually he was made entirely out of tin - but since it was a gradual process, he's still human Nick Chopper and not a new person. Even more paradoxically, however, and with more than a bit of Fridge Horror, the tinsmith kept the old head in a closet, where, due to the no-death nature of Oz, it remained sentient, desiring nothing to do with the Tin Man when he returned to retrieve it. His beloved eventually went on to marry a person assembled out of all the cut-off pieces.
    • In The Road to Oz, Jack Pumpkinhead is shown with a garden of new pumpkins grown to replace his head whenever the current pumpkin spoils. He claims that since the head is the smaller part of his body, he remains the same person. Also, in The Marvelous Land of Oz, one of his legs is used to replace the broken leg of Sawhorse, and is later replaced in turn by a table leg. Neither seems affected by the change.
  • Parallel Lives: The Trope Maker and Trope Codifier. The concept is described in a famous paragraph in his Life of Theseus:
    The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.
  • Played with in the Shannara books, when Morgan Leah says that every part of the ancestral sword of the Kings of Leah has been replaced multiple times—except for the actual blade, which is over three hundred years old and is still in perfect condition. This is what makes him believe that the story of Alannon enchanting the sword three hundred years previous is true (Which it is).
  • Siddhartha: Touched on towards the end. One of the keys to the titular character's (eventual) enlightenment is coming to understand that "you cannot step into the same river twice" (because the water which makes it up has kept flowing downstream)
  • So Long, and Thanks for All the Fish: Invoked with Marvin the Paranoid Android. Over the course of four books, the hapless robot has been thrown back and forth through time then left to fend for himself so frequently he is now 37 times older than the universe, and almostnote  every part of him has been replaced at least 50 times.
  • Hinted at in the Star Wars Legacy of the Force series. While flying Slave I in his introduction, Boba Fett muses that the only part of the ship that remains from his father's days of piloting it was the pilot's chair.
  • Tomorrow The World: Because the Austro-Hungarian navy is starved of funds thanks to weak commanders and political wrangling, they use 'official reconstruction' to build a new ship under the guise of repairing an old one. The sailing ship the protagonist is on has been broken up and rebuilt twice, yet keeps the same name to maintain the subterfuge. Naturally this trope is lampshaded.
  • A Year And A Day In Old Theradane a group of thieves is tasked with stealing a city street that is a Place of Power. Their solution falls on one side of this trope: Over the course of a few days, they steal and replace all of the cobblestones. When they're done, the street is still there, but all of the parts that made it up originally are gone, which destroys the location's magical power.

    Live-Action TV 
  • Black Lightning: In season 4, Jen's powers become unstable, causing her to explode. She reforms in episode 6 (which is appropriately named "Theseus's Ship") with a new physical appearance. Gambi states that for all intents and purposes, she is still Jen but her father has issues adjusting to the change. However, this is subverted when it is revealed that Jen has actually been replaced by an entity from the ionosphere. The real Jen returns to retake her place.
  • Cheers: Played for laughs when a con artist tries to sell "George Washington's Axe," but then has to explain that all the parts have been replaced over the centuries.
  • Doctor Who: Discussed and played straight in the episode "Deep Breath". The antagonist of the episode is harvesting human organs to be able to pilot the ship, but in doing so, he has replaced most of the ship, and of himself. The Doctor lampshades this by saying "If you have a broom, you replace the handle, and then you replace the brush, and do it over and over, is it still the same broom?" The subtext of the conversation concerns the Doctor themselves, who periodically regenerates, taking on a new appearance and personality. It's been said that the process replaces every cell in their body, yet they remain fundamentally the same person. During the episode in question, the Twelfth Doctor was newly regenerated and uncertain of his true identity.
    • Played for Drama in the moment immediately succeeding this speech. The Doctor holds up a metal platter to have the antagonist look at himself in the reflective surface only for the camera to cut to behind the Doctor, showing that the other side of the platter is just as reflective and the Doctor may as well have been talking to himself.
    • Unlike the previous three Doctors, identity was a major theme of this Doctor's arc, centring largely around the Theseus' Ship Paradox.
  • Gotham Played for horror when the Dollmaker punished one of his subordinates by subjecting him to the Body Horror of replacing most of his body parts with incompatible pieces.
    Dollmaker: How much of you can be replaced before you're not you anymore?
  • Only Fools and Horses: The best-known example, where Trigger, one of the characters, is given a medal for owning the same broom for 20 years, although it has had 17 new heads and 14 new handles. When asked how can it be the same broom, Trigger holds up a picture of himself and his broom and says, "Well, here's a picture of it, what more proof do you need?" As a result, the paradox is commonly known in the UK as the "Trigger's Broom Paradox".
  • The same joke appears in David Jason's previous sitcom Open All Hours:
    Granville: We need a new brush.
    Arkwright: Nonsense! That's a marvelous old brush, that! I've had that for fourteen years. It's only had two new heads and three new handles.
  • Robot Wars
    • During an interview about Matilda on the "House Robots" special DVD, it was mentioned that she'd been upgraded so extensively over the course of the first five series that barely any of her original parts were being used at all. When the presenter joked that the only remaining original part was the strap holding the back of her shell on, her supervisor admitted that even that wasn't there originally; it had been added for Series 4 to stop the shell falling off every time she was flipped.
    • When the series was rebooted in 2016, all-new and massively updated versions of Sir Killalot, Shunt, Dead Metal and Matilda were created to face the new generation of competitors. Despite being completely new machines incorporating no components of the long-retired originals, nobody ever questioned that they were the same House Robots "returning" to fight again.
  • Star Trek from the beginning has begged this question ever since it was described how the transporters work. The transporter's function on the show was to be a magic elevator that took the away team to the planet without requiring the director to film a shuttle landing over and over again. The transporters work by dissolving the away team member and assembling a copy of them on the planet below, which makes you wonder if the same consciousness is moved also. Further questions are begged when you consider that in an episode of Star Trek: The Next Generation, a glitch in the transporter created a copy of William Riker who was marooned on the space station he was transported from, with tests affirming that both Rikers should be considered to be the 'real' one as nobody could determine a difference beyond the fact that one had been trapped on another planet for eight years. Yet more questions are begged when one episode features the only POV shot in the entire series of someone going through the transporter and mid stream being bitten by the Monster of the Week which suggests that the experience of being transported has no break in consciousness. There have also been two instances of conversations continuing between beaming subjects mid-beam in the TOS movies; Kirk explaining the "By The Book" subterfuge to Savvik in Star Trek II, and the badly timed rescue beam-out from Rura Penthe in Star Trek VI.
    • Star Trek: Deep Space Nine: Kira's Romantic False Lead Bareil Antos gets injured and has part of his brain replaced with cybernetics. As more of his brain fails and is replaced, the less he's him. Eventually he's mostly cybernetics, and rather than continue the process Kira allows him to die.
  • Invoked but defied in Power Rangers Operation Overdrive after the android Red Ranger Mack is 'killed' in the final battle; Mack's overall body still appears intact, so there should be nothing to stop Hartford (his creator/father) using his body and reactivating a new consciousness, but Hartford makes it clear that anything he recreated that way wouldn't be Mack, but just "something that looked like him".
  • In the final episode of WandaVision. The Westview Vision has the same essential personality and thought process as the original Vision, but physically he's a magical construct that Wanda Maximoff created in her grief. Meanwhile, White Vision is a Blank Slate who rigidly follows his programming, but he's physically the reanimation of the original Vision's synthezoid corpse. When White Vision reveals to Westview Vision that he has been ordered to "kill the Vision", Westview Vision counters that, as his opponent, he is only a conditional version of Vision leading to a namechecked discussion of this trope which causes White Vision's thinking to become caught up in the paradox of who is the real Vision. However, this exchange introduces a third aspect into the discussion, the concept of memory and experience. So when White Vision accepts Westview Vision's offer to gain full access to the Vision's memories, White Vision undergoes a defined change. His previously cold, white eyes become full of color and warmth as White Vision declares "I am Vision" before flying off. The scene leaves it unclear if White Vision is now a unification of thought, material and memory raising the question as to whether the Original Vision is still dead in the MCU... or did White Vision who now identifies himself as the true Vision fly off to destroy himself and fulfill his programming?.
  • Westworld Dolores Abernathy has been repaired so many times over the years that she's practically brand new, with at least one character noting that she's one of the "older" robots in the park purely on a technicality. It remains to be seen how much, if anything, remains of her original components or programming.

    Music 
  • When the band Underoath released their album Ø (Disambiguation) in 2010, none of the founding members who played on their 1999 debut release remained, having all been replaced one-by-one throughout the band's career. The last one, drummer Aaron Gillespie, voluntarily left the band earlier that year without contributing to the record (Gillespie has since returned to the band, and remains the last original member).

    Radio 
  • The BBC Radio 4 cryptic connections quiz Round Britain Quiz had a question based on this in episode 8 of the 2021 series, asking "Why might a Peckham road sweeper's chief tool, tin in the land of Oz, and the vessel of an ancient Greek hero, not be quite what they seem?" The answers are Trigger's broom, the Tin Woodman, and the Ship of Theseus itself.

    Tabletop Games 
  • In the BattleTech novel Close Quarters this is referred to with an old Jenner 'Mech which is "one of the first" ever made—except that every single part, down to even the last nut and bolt, has been replaced over the last 600 years two or three times or more!
  • Dungeons & Dragons: There is a race of aberrations called the Tsochar who are colonies of unintelligent worms fused together to form an intelligent larger worm. The individual worms have a limited lifespan but the colonies can live forever by replacing any worms that die so any sufficiently old Tsochar will be composed of none of the worms that originally formed it.

    Video Games 
  • In Fallout 4 and Fallout 76 some weapons have bonus effects, which are preserved even if you replace every component of the weapon with a different one, even going so far as to turn a wooden bat metal.
  • In Haven (2020), Kay discusses this paradox with Yu by asking if she believes the Nest, her personal spacecraft, is the same as the one she first fixed up as a teenager, given how many of its parts she's replaced over the years. She can direct this question back at him.
    Yu: What about you? Are you still Kay?
    Kay: Huh?
    Yu: Your body cells are constantly renewing aren't they? Ever since you were born, you probably don't have that many cells in common with the Kay from the beginning.
    Kay: ...
    Yu: (smugly) Try thinking about that one.
    (cut to much later; it is now nighttime and Kay still stands in the same spot pondering the implications)
    Yu: (waving at him from the Nest) KAY, PLEASE! IT'S LATE! YOU NEED TO COME HOME!
  • Mega Man Zero 3 reveals at the end of the game that Omega's true form is Zero's original body, Zero having been uploaded into a copy body prior to the events of the Zero series. Defeating Omega means destroying his own original body. Fortunately, X appears to reassure Zero that he's still Zero despite his copy body, and Zero carries through with destroying Omega.
  • Megatraveller The Zhodani Conspiracy: (Based on the Traveller game), if any of your party members dies you can recruit a replacement at the spaceport, who will carry on in their stead just as good as anyone else. But if all of the original members are dead, the game ends even if everyone else is alive. The recruits just don't have the same commitment to the original quest.
  • In NieR: Automata, the merchant in the Resistance camp has a damaged leg which he is reluctant to replace as it is the last remaining piece of his original body, and he ponders whether he would still be himself without it.
  • In SOMA the main character, Simon, is revealed to be a robot with the memories of the original Simon, who had his brain scanned and then died almost a century before the events of the game the topic is brought up several times, most notably when Simon changes into a new diving suit(read: body), only to discover that the process actually involved making a copy of his mind and uploading it, leaving the original body alive. The player is left with the choice of abandoning it or ending its suffering.
  • In Yandere Simulator, Ayano can speak online with Selene2005, who brings up this paradox as an alternative discussion topic instead of their… preferred topic of discussion.

    Visual Novels 
  • Lucy and the protagonist end up having a discussion on this in Lucy ~The Eternity She Wished For~, since over time Lucy could end up having her entire body replaced part by part, and even her memories can be deleted or modified. By the end of the game, Lucy is destroyed completely (even her memory chips are fried and unsalvageable,) and the protagonist spends the next 15 years learning robotics to try and recreate her from scratch with her memories intact. At first, it seems like he only succeeded in creating a mere copy of the original Lucy, until he's finally able to trigger her memories to come back.
  • One of the many digressions that comes up during Nine Hours, Nine Persons, Nine Doors involves the Ship of Theseus.

    Webcomics 
  • Girl Genius: Tarvek would be the first to admit that Anevka has been... different since being given a puppet clank body after her "accident." Though the real problem is that as Anevka slowly sickened inside her life support chamber, her clank body took up more and more of the slack until even the clank failed to notice that Anevka had died — and the clank was becoming increasingly erratic. Tarvek shut her down for safety's sake as much as anything else.
  • Saturday Morning Breakfast Cereal parodies this here by having an alien claim that humans only live about sixteen hours. Sure the body persists for decades, but if life is continuity of consciousness and humans spend eight hours a day unconscious than over those decades 30,000 people or so will inhabit it. The votey reveals he's just messing with her.
  • Schlock Mercenary: The first warship seen owned by the Tagon's Toughs was the Dragon-class cruiser Kitsefear. After her destruction early on in the comics, she was eulogized in a footnote that mentioned that "her hull had been patched so many times it's hard to say where the original hull sits."

    Web Original 
  • Something of a theme in gen:LOCK when it comes to the titular gen:LOCK technology. One can even see the phrase "Ship of Theseus" pinned to a wall in Dr. Weller's lab. As it turns out, when the gen:LOCK program first got started, the doctor made a habit of uploading Chase's mind into two cyberbrains simultaneously, one running a Holon, and the other a spare copy. After the Union captured Chase (eventually turning him into the Nemesis), Dr. Weller uploaded the copy back into Chase's body and kept it a secret. So the question becomes: which mind is the real Chase? Both? Neither?
  • Matt Santoro discusses this paradox in his video The 10 Most MIND-TWISTING Paradoxes of All Time!.
  • This trope is alluded to by CinemaSins in their sins video for Cars:
    "Also, if every part of these cars are actual living appendages and need to be changed periodically, like the tires — it really starts to make you ponder the question, 'If I replace all the parts of an old car, is it the same old car or is it a new car?'"
  • Cobra Kai ended up with such a case in the third season. Johnny's sensei Kreese didn't just swipe the dojo behind his back; he effectively replaced all of Johnny's students — a Ragtag Bunch of Misfits with no goal other than to be able to fight back against a bullying epidemic — with the very types that were at the heart of their core issue.
  • On the Dream SMP, as the nation L'Manburg gets trashed time and time again and exchanges one president for anothernote , more and more of it gets replaced until it's borderline unrecognizable. For the time being, it seemed to avert fully being replaced thanks to the L'Mantree, a remnant of L'Manburg from Wilbur's presidency that survived even when everything else was blown up or torn down. However, when the L'Mantree is burned down by Niki in the Doomsday War, the L'Manburgians realize that nothing is left of their original nation and that it's no longer worth salvaging its ruins.
  • Discussed Trope in Stray Ami - Blank and Andale decide it's different with people.
  • There is a Vsauce video discussing a variant: Imagine you have the atoms in your body removed one at a time each atom is replaced by an identical one in the exact same place. At what point would you no longer be the same person, if ever?
  • Mike Burn Fire was once soundly chastised by Zach for taking this very approach to alcohol consumption.
    Mike: I don't remember the specifics of it, but I remember something along the lines of "If I put alcohol in this cup again, it's still the same cup, so it's just one drink," right? So 'three' drinks in...I was puking quite a lot and screaming "WHY DO PEOPLE DO THIS?" Long story short, Kirk let me stay overnight.
    Zach: You can't Ship of Thesus a drink, Mike!

    Western Animation 
  • In the Bump in the Night episode "Farewell, 2 Arms", Molly gradually replaces bits of her body with tougher parts in order to become stronger. As she does so, she gradually becomes more and more cruel and domineering. This culminates in her ripping off her own head, the last part of her original body, and replacing it with a staple remover. Squishington manages to reattach the head to her original body, which resets Molly to her original, gentle personality. She then confronts the form she made over the course of the episode, which is still rampaging, and claims to be what Molly always wanted to be. Molly admits she was wrong.
  • Joked about in an episode of Family Guy. Joan Rivers was doing interviews on the red carpet of the Adult Video Awards, and said that she was once asked to do a porno but couldn't because, since she's had so much plastic surgery, more than 50% of her body was under 18 years of age.
  • Invoked in the Futurama episode "The Six Million Dollar Mon", in which Hermes continually "upgrades" himself by replacing various organic parts with robotic prostheses. As each human part is removed, Zoidberg salvages it and stitches them back together. After the final organic piece of old!Hermes, the brain, is replaced and reattached to new!Hermes, there are two Hermeses: an organic one with all the parts of the original (plus a whole lot of stitches), and a robotic one controlled by the processor of the psychopathic robot Roberto.
  • Gerry Anderson's New Captain Scarlet: Both Captain Scarlet and Captain Black are killed and resurrected by the Mysterons. According to Dr. Gold, the revived Scarlet technically isn't Scarlet but isn't a clone either. Scarlet in one episode expresses concern that he isn't human and Captain Black in another episode admits to not really feeling like a Mysteron at times.

    Real Life 
  • American philosopher Theodore Sider proposed a solution to this paradox by considering objects from a four-dimensional perspective rather than a three-dimensional one. If objects are thought of as a four-dimensional "river" of three-dimensional "time slices," then each "slice" could still be part of the "river" while remaining unique from one another. In this way, an object can still be considered itself even when all of its components are eventually replaced. Another way to put it is that the essential "identity" of something can "fix itself" over time, as long as the process is gradual. One practical way to look at it is product brand refreshes. The whole "new look, same great whatever" depends on consumers recognizing the refreshed packaging as the same product, getting used to it over time, and then the process repeats again down the line.
  • It's commonly held that the human body replaces all of its cells (in some versions, all of its atoms) at regular intervals, usually given as either seven or ten years. While cells do continually die off and are replaced with new ones, they do so at different rates, with no regular cycle of years. There are also exceptions, such as neurons in the brain and parts of the skeletal structure, which last a lifetime and are not replenished. Therefore, after a few decades, a person will be composed of almost entirely different physical matter.
    • Some have used this fact to metaphorically say "Buzz Aldrin did not walk on the Moon" — with cell replacement he's not the same physical being that once walked on the Moon.
  • A number of wooden vessels built during the Age of Sail exist to this day, but over the course of their lifespan they have had numerous refits in which timbers in disrepair or rot were replaced with new material:
    • The first rate ship-of-the-line HMS Victory, the oldest actively commissioned warship. In a 2009 interview, one of her commanding officers, Lt Cdr John Scivier, estimated that 10 to 15 percent of her hull remains original.
    • The frigate USS Constitution, "Old Ironsides," is the oldest active commissioned warship still afloat and sailing. The Naval History and Heritage Command's Boston detachment has also estimated that 10 to 15 percent of her hull is still original.
    • Unlike Constitution and Victory—which most agree are not replicas—the War of 1812-vintage brig Niagra is more commonly considered a replica rather than the restored original. Her third reconstruction in 1986 found that most of the wood comprising her hull was badly decayed, and so the ship was almost completely rebuilt save for various non-structural timbers which were salvaged and reused.
    • USS Constellation is even more complicated and a little controversial. According to the US Navy's records, the 1797 frigate USS Constellation was given a major refit in 1854 turning her into a sloop of war. However, some contemporary accounts and analysis of the current ship indicates that USS Constellation was broken and up and sloop of war built from her timbers plus some in Navy stockpile. This was done as a scheme to secure funding from a congress that might have been wary of funding construction of an entirely new vessel. It's now more common to list the frigate and surviving sloop as different vessels.
    • For a slightly more modern example, the Japanese Museum Ship Mikasa was a pre-dreadnought battleship that fought in the Russo-Japanese War, and having been retired from service following the Washington Navy Treaty of 1922, Mikasa was permanently moored in Yokosuka. She fell into disrepair following World War II and was extensively rebuilt in 1961.
    • The Russian Cruiser Aurora, built in 1903, was sent for repairs in 1984. Her hull was so deteriorated that it was determined to be cheaper to simply cut the hull out below the waterline and sink it out at sea, then replace it with a new hull based on preserved blueprints. So now there's the Aurora docked in St. Petersburg....and the wreck of the same Aurora in the Gulf of Finland.
  • Same as above for medieval cathedrals in Europe, particularly those of old city centers where modern pollution accelerates the degradation of stone. Many of the Middle Ages stones and statues have been replaced by others with restoration processes since the 19th century.
  • There have been cases of multiple different automobiles each having a claim to being the "original" vehicle driven by a famous celebrity or racer, as a result of the vehicle having been broken down for parts at some point, leading to there being, for instance, one vehicle based upon the original chassis, another with the original bodywork, and a third with the original engine.
  • Buddhism considers every aspect of reality to be affected by this, but with a special focus on humans and our personalities, since we constantly change at a slow but steady rate. So are you the same person you were ten years ago? Interestingly the solution offered is that you aren't, and that your 'self' as you usually see it is an illusion. On a broader note, since everything is constantly changing nothing can really be said to exist or be stable, and trying to deny this or ignore it causes suffering.
  • Pop groups can get like this - the Sugababes have replaced all three original members while keeping the same name (the three originals subsequently reformed as a new band and attempted to sue to get the name back, unsuccessfully), while there's at least six different iterations of the Four Tops floating around.
  • One way to look at this problem from a computer science perspective is to look at the difference between call-by-value and call-by-reference. Call-by-value passes in data from a location in the computer's memory, usually by copying it to a new location temporarily. Call-by-reference passes in the location itself, which will probably work the same way unless the data in that location changes later on. So how do you tell if two variables are "the same?" Depends whether the data or the location is important, and there are cases for both. Some languages, like Javascript, even have separate "equality" (==) and "identity" (===) operators just for this purpose.
  • Happened to Douglas Adams when he visited Kinkaku-ji in Japan (which he wrote about in his non-fiction book Last Chance to See), and found that it looked suspiciously new. He asked about it and was told that the building burned down, and was rebuilt from all-new materials. And that this had happened multiple times. He asked how it's the same building then, and was told "It's always the same building". Adams concluded that someone was missing the point, but that it might have been him.
    "The intention of the original builders is what survived. The wood of which the design is constructed decays and is replaced when necessary. To be overly concerned with the original materials, which are merely sentimental souvenirs of the past, is to fail to see the living building itself."
  • The members of the Progressive Rock band Yes have come and gone so often that the band has been compared to a musical version of the Ship of Theseus. The current lineup features none of the founding members. Indeed, many prog-rock, heavy metal and classic rock groups of the late 60s and early 70s still active in the present-day are this by default, due to original line-up members leaving, retiring or being deceased.
  • Wiki articles. Because they're communally edited, over time they may get to a point where very little of the original wording will have been written by the original writers of the article, even if only small bits are edited at a time rather than the page undergoing a complete overhaul.
  • Sports teams. Can the identity of the team really maintain continuity even as players and managers come and go? Are the Chicago Cubs who won the World Series in 1908 and the Chicago Cubs who won the World Series in 2016 the same team in any meaningful sense?
    • This is further complicated when team names and team compositions are divorced from one another due to being moved. For example, when the old Cleveland Browns moved to Baltimore, they could not take the name with them, rebranding as the Ravens.
    • Stadiums can have the same issue, with redevelopment and upgrade works over the decades raising questions as to just how "historic" a ground really is - is Manchester United's Old Trafford, originally built in 1910, really that same stadium if all four stands have been demolished and rebuilt since the 1990s?note 
      • Fenway Park in Boston is the oldest Major League Baseball stadium still in use, being the home of the Boston Red Sox since 1912. But since every part of the original ballpark has been replaced over the years (many more than once), is it really the same stadium?
  • The book Pink Floyd and Philosophy discussed this in a chapter devoted to Pink Floyd's lineup. The conclusion was that Pink Floyd could be said to be Pink Floyd as long as either David Gilmour, Richard Wright, or Nick Mason were present. The chapter's title: "The Dinner Band on the Cruise Ship of Theseus."
  • Stephen Fry once wrote an article in which he describes the phenomenon as "P.G. Wodehouse's Typewriter", and claims that, since every cell in the human body dies and is replaced at some point in your life, the embarrassing photos of him playing naked in the garden as a child (that his mum used to love showing to his friends when they came to visit) are technically not photos of him.
  • In Bruce Campbell's memoir If Chins Could Kill: Confessions of a B-Movie Actor, there is a section entitled "You Will Never Kill My Classic", which focuses on Sam Raimi's 1973 Oldsmobile Delta Royale, dubbed "The Classic". He describes its extensive onscreen appearances in Raimi's films from his homemade Super-8 films to modern blockbusters, and several cases of the car having to be stripped down, modified or rebuilt with new parts, either due to Raimi's filmmaking needs or, in one case on the set of Crimewave, as a prank by Campbell himself, prompting Raimi's stubborn insistence to Campbell that "you will never kill the Classic". By the time of the shooting of Evil Dead 2 it no longer ran, but Raimi insisted on its inclusion, even if it meant maintaining the vehicle at his own expense, which he did. Campbell later teases Raimi in a quote about how much of the Classic consisted of original parts, with Raimi cagily insisting the body and chassis, dash and steering wheel are all original, that the rest of the car contains "some" new parts, and that the Classic currently resides "in a warehouse somewhere in Southern California."
  • Valve's Source Game Engine was developed from the "GoldSrc" engine used for Half-Life 1, which itself was a heavily modified version of the original Quake I engine. Per John Carmack, there are still bits of early Quake code in Half-Life 2. Valve have had no legal issues licensing Source to other developers, suggesting that it's different enough to not be an issue.
  • Many PC gamers will acknowledge that their rig is somewhat of a "Computer of Theseus". Over time, individual parts will be replaced such as the GPU, hard drive, RAM cards, etc. At what point does it stop being the same computer they originally built? Was it when the Operating System was reinstalled, or when the chassis was replaced?

 
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Alternative Title(s): Ship Of Theseus

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Vision & White Vision

The theory is discussed and used to make the White Vision realise that he is the real Vision.

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