Theseus' Ship Paradox

aka: Ship Of Theseus

Art by pastillustrator

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?

— Only Fools and Horses, "Heroes and Villains"

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?

The Ship of Theseus is a classic philosophical thought experiment about the nature of identity. 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?

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. A literal example of the trope may be a Franken-vehicle.

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Examples

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 that happens to have the handlebars and brake pads of a Honda Supercub.
• 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, in which 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 it is a rare type of gem, so it is very important that they avoid fracturing as much as possible due to its 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 Stanley Holloway's "Beefeater" monologue, 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?
• Doom Patrol: Robotman notably had his brain destroyed by the Candlemaker near the end of Grant Morrison's run and survived by having his consciousness transferred to a computer system, with Rachel Pollack's run later backpedaling his being completely robotic by giving him a new organic brain to store his memories in. The issue on whether he's still Cliff Steele wasn't addressed until the 2023 Halloween anthology DC's Ghouls Just Wanna Have Fun, where his story has him haunted by the ghosts of deceased Doom Patrol members and one of the ghosts is of himself, his death cited as occurring when the Candemaker destroyed his original brain.
• 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 injuries start piling up, Von Braun has replaced 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 Mighty Thor: The Loki of here and now isn't the same Loki who originally menaced Thor back in the 1960s. That Loki died quite comprehensively in 2010, getting torn in half by the Void. The current Loki... well, that's complicated, but is basically a magical copy of Loki reborn as a child, who then got taken over by a copy of the Original Loki's memory, but now with guilt and empathy that made them distinct from both. A long and vicious struggle for identity followed, as this new Loki had to determine whether they were Loki or their own person (not to mention dealing with everyone else's feelings on the matter. Is a recreation of Loki responsible for the crimes of the original, for example.)
• 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 regard 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?"
• Brought up in X-Men Forever regarding Storm being split into three different figures; "Perfect Storm" is essentially a clone created by the Consortium, while the original Storm's body is regressed to an amnesiac teenager and her mind and essence is converted to an energy form that is provided with an artificial body by Tony Stark, the energy form eventually merging with the teen Storm to restore them both to adulthood.
• Immortal X-Men touches on this when Charles Xavier is talking with a mental projection of Mister Sinister regarding Moira McTaggert's current genocidal approach towards mutants, wondering if she even really counts as Moira any more after she was transferred into a robot body after losing her original mutant power of rebirth. Sinister notes that given his own habit of frequent self-modification, he's not the best person to ask, bringing up the paradox. And then, Sinister being Sinister, he gets distracted by his own metaphor.

Fan Works

• Discussed in A Courier For Kivotos. Arona questions the Courier if the rebuilt ED-E would be the same entity as the Wasteland version since it was remade with Kivotos tech and parts. The Courier still thinks of the new ED-E as the same owing to the backed-up personality/memory core that he installed into the new body.
• 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. Does that make him a clone rather than 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.
• The Rise of Darth Vulcan: Ted quietly laments over the fact that due to him having lived in Equestria for at least a year, his entire cellular structure had been slowly rewritten with new cells made from ingesting Equestrian foodstuffs, replacing the old cells that was made on Earth. And that because of this, Ted is unable to find his way back to his Earth on his own.

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 talking about being in their fifties, and 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

• 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 or Ultron. Ultimately, Avengers: Infinity War establishes that he's comprised of the minds of Tony, Bruce, Ultron, JARVIS, and the Mind Stone.
• 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 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.
• Luzzu: Jesmark tells a version of the trope-naming tale to his infant son, about a famed but decrepit ship that eventually had all its parts replaced. Given that Jesmark had spent most of the movie trying to get his old luzzu repaired after it started leaking, it's obviously a way for him to think aloud about whether or not his old boat and the way of life it represents is worth preserving.
• 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.

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?
• In the BattleTech Expanded Universe 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!
• 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 "The 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.
• Discworld:
  • Discussed in Soul Music, about the harps of Llamedos:
    Most of the harps were old. It wasn’t as if they wore out. Sometimes they needed a new frame, or a neck, or new strings — but the harp went on.
  • Brought up several times in The Fifth Elephant:
    • 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."
  • Throughout the Witches series, Granny Weatherwax's broom has been unreliable to the point of needing a bump start every time, despite every part having been replaced multiple times. 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 by replacing every single part at the same time. 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 begins by 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.
• Land of Oz:
  • 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.
• 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.
• Hinted at in the 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.
• The English Little Red Engine picture book series about a sentient locomotive includes a title The Little Red Engine Goes to be Mended, in which the author seems to be deliberately exploring this trope. A trip to India has caused the Little Red Engine to be covered in rust after being left outside during the rainy season. It is loaded onto a ship to England and 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 are taken away. We are told explicitly that its original name and number have been taken to the brass shop for actual restoration. One major part, the boiler, is mentioned to have been taken away to the boiler shop, suggesting that an attempt may have been made to restore it. Also, when Sam Trigger, its driver, comes to see how things are progressing, he is told that "the 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 various parts being built more or less from scratch.^note The author specifically mentions a new frame (a major component), the steel outer shell of the firebox, and possibly the copper inner shell, brake blocks, a connecting rod, a drag hook, some or all components of a wheel pair, new stays, studs, pins and bolts, and oil trimmings 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 has 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.
• The Misfit of Demon King Academy: Referenced when Anos disintegrates an opponent, then immediately resurrects him, then repeats the cycle to torture him. During a break, Anos makes the guy paranoid and scared by asking if he thinks he is his original self or a copy.
• Parallel Lives is 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).
• Touched on towards the end of Siddhartha. 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 that 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 almost^note Except the pain-raddled diodes down his left side every part of him has been replaced at least 50 times.
• 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.
• In 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 (2018): 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.
• Cobra Kai ends up with such a case in the third season. Johnny's sensei Kreese doesn't just swipe the dojo behind his back; he effectively replaces 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 who were at the heart of their core issue.
• Doctor Who:
  • Discussed and played straight in "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 the above speech. The Doctor holds up a metal platter to have the antagonist look at himself on 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 is a major theme of the Twelfth Doctor's arc, centering 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: When do you stop being you and become something new?
• Only Fools and Horses: 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 it can 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 from Only Fools and Horses 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.
• 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".
• 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, the franchise has begged this question ever since it was described how the transporters work. The transporter's function is to be a magic elevator that takes 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 midstream 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 Saavik in Star Trek II: The Wrath of Khan, and the badly timed rescue beam-out from Rura Penthe in Star Trek VI: The Undiscovered Country.
  • In the Star Trek: Deep Space Nine episode "Life Support", 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. He eventually winds up mostly cybernetics, and rather than continue the process, Kira allows him to die.
  • Star Trek: Picard:
    • Out of universe, the paradox was invoked by Memory Alpha editors when, in the first season finale of Star Trek: Picard, Jean-Luc Picard's human body dies of a long-gestating neurodegenerative disease, but Noonien Soong's son electronically transfers his mind into a "healthy" robotic body resembling the old body, a perfect example of the Body Backup Drive trope. The editors argued over whether to create a separate article for each body or not, with the franchise's precedents for either side being evenly matched, before coming to a consensus to leave Picard's article un-split, with additions where appropriate. The Clone Angst is actually brought up in-universe on occasion in the second season, but Picard's original corpse becomes the driving MacGuffin behind the plot of the third season.
    • In the last 2 episodes of season 3, the USS Enterprise-D returns, thanks to Geordi having spent over 20 years restoring her after her destruction during Star Trek: Generations. It's likely that parts from a number of decommissioned Galaxy-class ships went into restoring her; the stardrive section was cannibalized wholesale from the U.S.S. Syracuse since the Enterprise's original was destroyed by a warp core breach detonation. Now... the parts are all the Enterprise.
• Discussed in the final episode of WandaVision, with an extra twist where the pieces removed from the Ship of Theseus are then used to build a second ship, which has equal claim to being the Ship of Theseus. 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. Westview Vision uses the Ship of Theseus parable to explain the situation to White Vision, 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. 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. This is used to both obscure and foreshadow The Reveal in Season One that events featuring Dolores are actually taking place decades apart.

Music

• In Flames was formed in 1990, and by 2010, the last remaining founder had left the band.
• Judas Priest was first formed in 1969, broke up 7 months later, and reformed in 1971 with only one original member left, that being lead vocalist Al Atkins. If that name sounds unfamiliar, that's because he was replaced by Rob Halford in 1973, still a year before they even released their self titled debut album.
• Lynyrd Skynyrd was formed in 1964. In March 2023, founding guitarist Gary Rossington died, leaving the band with no living founders.
• Napalm Death lost all its original members between its formation in 1981 and its first album in 1987. The lineup continued to change during the recording of that album and everyone who played on it has long since left. Bass player Shane Embury joined shortly after to tour that album and is the only member remaining from that lineup. The lineup has been far steadier since the early '90s, three out of four members having been in the band since at least 1991.
• Rockapella (the vocal group from Where In The World Is Carmen Sandiego) has no original members left. Although tenor Scott Leonard has appeared on all their albums, he joined the group five years after forming.
• German electronic prog band Tangerine Dream was founded in 1967. Its last original member, Edgar Fröse died in 2015, but it did not stop the band from existing. They published their 86th LP in 2022.
• 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).
• The Velvet Underground album Squeeze involved no original members. Doug Yule was not just the only player who had played on any other Velvet Underground album, but also practically the only person involved, having written all the songs, played and sung almost all the parts, and produced the album.
• The members of Yes have gone in and out of the lineup so often (from their debut to Drama, they never had a consistent lineup for more than two albums) that the band has often been described as a real-life Theseus Ship Paradox; until his death in 2015, Chris Squire was the only member who'd appeared on every album. 2021's The Quest marked the first Yes album without any of the band's founding members.

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 BattleTech, this question dogs the famous Yen-Lo-Wang, a Centurion that is over a century old by the Dark Age setting. Tracking its modification history, there is no part of the 3150-era 'Mech which is the same as the original 3028-era 'Mech. The armor, chassis, engine, and myomer musculature have all been exchanged in modifications. The changes made to the engine necessitate a new gyro. The cockpit was swapped several times to accommodate the modifications. The current iteration of the 'Mech has no weapons in common with the original. Theoretically, a very dedicated person could track down the original parts and rebuild a second, 3025-vintage Yen-Lo-Wang in 3150, as not even the iconic razor talons were kept between upgrades... so the only thing that allows the 'Mech to be called Yen-Lo-Wang is the family history that is handed down with it.
• 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.
• Warhammer 40,000: Evilutionary Biologist Fabius Bile has kept himself alive in the ten millennia since the Horus Heresy through a combination of cloning and Body Surfing, due to suffering from an incurable gene cancer called the Blight. The question of whether the current Bile is the real one or not gets bandied around, with Bile ultimately not caring enough to give an answer.

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. Actually, you two may not have a single cell in common. So, are you still Kay?
  Kay: ...
  Yu: [smugly] I'll let you ponder 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, WE NEED TO GO HOME NOW! YOU CAN THINK ABOUT THAT TOMORROW, OKAY?
• Idol Manager: The rival points out that all idols in a given Idol Singer group will eventually graduate and any of the people involved in major backstage work can potentially quit. Hence, they ask if the Player Character's group will still be that same group if all the starting idols graduate and the Player Character quits, but the group continues under that name with other people.
• 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.
• In Megatraveller The Zhodani Conspiracy (based on the Traveller game), if any of your party members die, you can recruit a replacement at the spaceport who will carry on in their stead just as good as anyone else. However, 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, 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 The Talos Principle, Milton can ask you if you would stop being human at some point if your brain was slowly replaced with nanomachines that performed the exact same function as the cells they replaced. You are allowed to answer in the affirmative or negative, and the question builds on the Central Theme of "what makes us human and could a robot be human?"
• 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 in Nine Hours, Nine Persons, Nine Doors involves the Ship of Theseus.

Webcomics

• Existential Comics: The first comic takes this trope and runs with it. In a hypothetical future, a teleporter is invented and revolutionizes transportation, but a protest movement arises out of people who claim that the machines are actually killing people and replacing them with clones, as their entire atomic makeup is transformed. One of the protestors confronts the inventor of the device in a bar, who argues that the important part is the emergent pattern, not the precise individual atoms, that make up a person, and he admits that while there's an interruption of consciousness, it's comparable to being knocked unconscious or a good night's sleep, and that if the persistent self survives that, then it certainly survives the teleporter. The protestor freaks the fuck out at the implication that sleep is the equivalent of death for his consciousness, and he spends the rest of the story wrestling with it until he's finally able to come to terms with it.
• 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.
• Sandra and Woo: Discussed here with the examples of computer hardware and people.
• 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".
• xkcd: "Messier Objects" argues that the Messier catalogue contains all objects (and not just the 110 astronomical objects charted by Charles Messier). The Alt Text says that "the debate over the correct Messier number for the Ship of Theseus is ongoing."

Web Original

• Campfire Stories: Mike 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 Theseus a drink, Mike!
• 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?'"
• On the Dream SMP, as the nation L'Manburg gets trashed time and time again and exchanges one president for another^note with founding president Wilbur being succeeded by Schlatt after the Election Arc, and Tubbo being made president by Wilbur after Schlatt's death during the Civil War that broke out as a result of Schlatt's presidency, more and more of it gets replaced until it's borderline unrecognizable. It avoids fully being replaced thanks to the L'Mantree, a remnant of L'Manburg from Wilbur's presidency that survives 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 nothing is left of their original nation and it's no longer worth salvaging its ruins.
• 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?
• jan Misali talks about this paradox frequently in their videos:
  • "how many Super Mario games are there?" uses it to describe the Mario vs. Donkey Kong series, which went through a Genre Shift from Puzzle Platformer to Lemmings-esque Teamwork Puzzle Game after its first instalment.
  • "who wrote Caramelldansen?" has Misali bringing it up while musing that the "Caramella Girls" could technically be considered the same band as Caramell, just with a new name and lineup. They then conclude that it's more like the Ship of Theseus was dismantled completely, then the ship's rights holders built a whole new ship because one of the Ship of Theseus's songs became an unexpected viral hit and they wanted to capitalise on it.
  • "the five kinds of paradox" classifies it under the second type of paradox: a question that isn't a logical contradiction, yet still has no correct answer. Misali also acknowledges that this is the third time they're discussing the topic in one of their videos.
    "mention this in three videos call that ship of threeseus"
• James A. Janisse discusses this in his episode of The Kill Count covering Child's Play 2 during Chucky's repair and reconstruction with the same underlying endoskeleton. Though he refers to it as "Abe Lincoln's hatchet" instead of Theseus' ship while using the broom metaphor of replacing the handle and later the head.
• Matthew Santoro discusses this paradox in his video "The 10 Most MIND-TWISTING Paradoxes of All Time!".
• In THE MONUMENT MYTHOS, the decommissioned prison island of Alcatraz is, in reality, a geographical superorganism that acts like a single-celled creature, performing a perverted version of mitosis on a massive scale referred to as "Alcatrazosis" in which the entire island starts to split into identical versions of itself. In the video ALCATRAZATTACK this process was projected to see the superorganism start to absorb the city of San Francisco by the year 2050, but after blasting the island with high doses of radiation the process became accelerated, and by 2003 Alcatraz has spread far enough to reach West Texas. It's never said what this actually meant for the country, although sounding like some sort of cancerous landmass of Alcatraz islands piling up on top of one another, it is instead much more subtle than that, it simply replaced everything in its path with its own materials, leaving it otherwise to look virtually unchanged. In ALCATRAZAPOCALYPSE it's realized that by 2022 Alcatraz had replaced everything in the United States up to the East Coast, and possibly even further, as Leonard Morlin realizes in horror every cell in his body is different to itself only three days prior. Unable to grasp that he has been effectively replaced without his knowledge Morlin suffers an existential breakdown, citing the 'Theseus Ship Paradox' by name to the American People before committing suicide.
  Leonard Morlin: I have just finished the last batch of tests and I can confidently say that I am not the same person as I was three days ago. Alcatraz had copied us all overnight. Every particle of this country and its citizens, replaced. The United States is the Ship of Theseus.
• Discussed 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?

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 does interviews on the red carpet of the Adult Video Awards and says 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 is 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 the old Hermes, the brain, is replaced and reattached to the 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, 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 indicate that USS Constellation was broken up and a sloop of war built from her timbers plus some in Navy stockpile. This was done as a scheme to secure funding from Congress which 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.
    • The US Navy used this trick many times in the 19th century. In 1874, five Civil War ironclad monitors (USS Puritan, Amphitrite, Miantonomoh, Monadnock and Terror) that had been sitting in reserve for the last 9 years were taken in for "repair". This involved scrapping the ships and building new more capable ones with the same names. USS Puritan was the most extreme example, being a full 50% larger than the original ship of the same name and not being an ironclad at all, instead having all-steel armor, along with having its main armament in 2 twin turrets whereas the original had its entire armament in a single twin turret.
  • 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.
  • Ezer Weizman's famous black Spitfire is not only on display at the IAF museum but also regularly flies in airshows, which means it's subject to more frequent repair and parts replacement than most museum pieces.
  • Britain's Royal Navy seems to take a position similar to that of the Japanese Shinto shrines listed further down the page — by longstanding custom, an actively serving ship inherits the battle honours of all prior ships of the same name, which can be interpreted by the philosophically inclined as all of them being different physical incarnations of the same ship even when separated by vast gulfs in time and space. Some ships have inherited honours dating all the way back to the Spanish Armada, while HMS Warspite (whose latest incarnation began construction February 2023) has the most of any single ship at 25 (of which 15 were earned by her nigh-indestructible 20th century battleship incarnation).
• 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. This also feeds into Japanese culture's view on the idea:
  • When Douglas Adams visited Kinkaku-ji in Japan (which he wrote about in his non-fiction book Last Chance to See), he 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 was 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 Ise Grand Shrine in Japan is deliberately rebuilt every 20 years, not just if it's destroyed.
  • Similarly, after the 2005 Naksan Temple Fire[1], the destroyed structures were rebuilt, with many of the burnt timbers placed on display. Foreign Tourists are told that the rebuilt buildings are the same.
• 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 eventually regained the rights to the Sugababes name in 2019, subverting this trope), while there's at least six different iterations of the Four Tops floating around.
• 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. Since the death of original bassist Chris Squire in 2015, the group has had no original members left. 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. Sometimes the title or URL may change as well. In a case of Self-Demonstrating Article, this happened to the Wikipedia page about the Ship of Theseus.
• 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?
  • In sports with faster roster turnover, teams can change even more quickly than that. In Super Bowl LIV, the San Francisco 49ers and Kansas City Chiefs played each other. When they played each other again in Super Bowl LVIII four years later, only 17 players of the 96 who played in Super Bowl LIV were still around for Super Bowl LVIII.
  • 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 football team moved to Baltimore, they could not take the name with them, rebranding as the Ravens. Three years later, a new Cleveland Browns were established, which are officially not considered an expansion team, but a restoration of the original team and retain all of the previous incarnation's history. Instead, it was the Ravens who were considered the expansion team. Officially the entire previous Browns coaching staff and players transferred to the Ravens, and then the Browns team was reactivated and had its roster filled via an expansion draft...despite not being an expansion team.
  • The NBA's Charlotte Hornets moved to New Orleans in 2002, and an expansion team was established to replace them in Charlotte in 2004, the Bobcats. But in 2013, the New Orleans Hornets were renamed the Pelicans, and the Hornets name and history were sold to the Bobcats, who became the new Charlotte Hornets. And were retroactively no longer and expansion team.
  • 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 possibly a bad example since Old Trafford is named for the area in which it lies, but the point remains.
    • 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, which itself was a heavily modified version of the original Quake 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.
• In late March of 2022, an open-source project that had completely reverse engineered The Legend of Zelda: Ocarina of Time and recompiled it for the PC was released, called "Ship of Harkinian" (named after both the Ship of Theseus and King Harkinian's line "Enough! My ship sails in the morning.") which has allowed every aspect of the game to be modified limitlessly. In November of 2023, after completely RE'ing the game, a second project to port The Legend of Zelda: Majora's Mask to PC was announced, given the working title "2 Ship 2 Harkinian".
• 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?
• Most guns avert this with a "receiver" ^note  Essentially the box that holds everything together, and generally contains the working parts inside it being the legal part of the gun. If this is destroyed, the gun is usually considered destroyed too.
  • The venerable Browning M2 heavy machine gun was originally invented near the end of World War I and has been in US military service for over 100 years. There are known examples of M2s that have actually been in service nearly that long, including one case where a Ma Deuce originally manufactured in 1934 had (based on inventory stamps) been sold to the pre-revolution Iranian Army, then captured by the Iraqi Army during the Iran–Iraq War, then acquired by Iraqi insurgents after the 2003 US invasion, and then captured by US Army soldiers who serviced it and put it on a turret ring within a week. In most such cases the receiver is likely the only original part.
  • The famous M60 machine gun has an unusually unreliable receiver due to it being welded together out of strips of metal. Thus the US military considers the receiver a replaceable part, which means that all parts of the M60 are replaceable parts.
• Rail preservation runs into this constantly, especially the older the locomotive or railcar gets. Even if the engine was built in the 1800s, it's likely that many of its parts were replaced throughout its working life, and then again in preservation into the 21st century. The amount of original parts might only be enough to count on a single hand in some of the more drastic cases. It's enough of an issue that some famous locomotives have been permanently removed from operation and placed on static display to ensure they no longer need part replacements and "original iron" is kept intact, although many argue that a static engine on a plinth is not the same experience as seeing it operational even if new parts had to be installed.
  • Locomotion No. 1, the first locomotive that ran on the Stockton and Darlington Railway in 1825, was preserved — but following major rebuilds and a boiler explosion, none of its current parts can be proved to date back to then. The current boiler dates from 1827 and was salvaged from a sister locomotive.
• Some civilizations and empires run into this. A dramatic example is the Roman/ Byzantine Empire. As the Roman Empire fell into decline, it was decided to split the empire into a western and eastern half. The western half, containing Rome itself, soon fell but the eastern half, centered in Byzantium/ Constantinople/ Istanbul, lived on. It even managed to briefly reconquer Rome and the rest of Italy in an attempt to revive a united Empire. However, most of the Eastern Roman Empire's/ Byzantine's thousand-year independent existence it did not control Rome or any of Italy north of around Naples. Speaking of the Roman Republic simply transitioned into the Roman Empire and was never formally declared defunct. But in the end, the Byzantines claimed to be Rome without speaking Latin, practicing the classical religion, controlling Rome, or wearing togas. When they were conquered, the subsequent Empire, known to history as the Ottomans, also claimed to be Rome, with the sultan claiming the title "Kayser-i Rûm" ("Caesar of Rome").^note Though this claim was deemphasized, if never formally dropped, as time went on. Originally, the Ottoman Empire was ruled by a Muslim sultan with a population that was largely Christian and as Roman, so claiming to be the new Rome made sense. The map of the Ottoman Empire under Suleiman the Magnificent also looks very similar to the Eastern Roman Empire under Justinian the Great a century earlier, and Ottoman sultans found the the Roman claim of "universal monarchy" (that is, the Roman emperor being the rightful ruler of the entire world, or at least to be of higher status than all other monarchs) to be quite appealing. But as the Muslim population grew to be the majority within the empire, and a rivalry began with Shia Muslim Iran, the Sunni Muslim rulers of the Ottoman Empire steadily increased their emphasis on Islamic rather than Roman titles. Then you have the various claimants to Roman succession, like the Holy Roman Empire. The Roman Republic and Empire are now both universally considered to be gone,^note Moscow also laid claim to being the "Third Rome" and thus the successor to the Roman Empire after Constantinople fell to the Ottomans, on the basis of being the only remaining Orthodox Christian empire, but basically nobody outside of Russia ever took that seriously. And few inside of Russia have taken it seriously either, after the Russian Empire fell in 1917. but when is a tricky question.
• An interesting (and usually tasty) variation is the perpetual stew. In brief, the stew was started at some point with some discrete set of ingredients, but as servings are scooped out and more/different ingredients are added, is it still the same soup? Some would say that as soon as the last of the original ingredients is gone it is no longer the soup it began as, but there is also the argument that it is not possible to remove all of the original ingredients (the broth has to have an unknown but present volume of meat, vegetable, and spice particles in it) preventing the original original soup from ever being completely gone.

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