What is the Ship of Theseus?

Have you ever looked at a picture of yourself as a tiny baby and wondered, "Is that really me?" Believe it or not, an ancient Greek puzzle about a wooden boat might hold the answer! Join Mira and Finn on Philosophy is Not Boring as they dive into the famous Ship of Theseus! Thousands of years ago, the people of Athens kept a hero's ship in their harbor. But as the wood started to rot, they replaced it piece by piece until not a single original plank was left. Is it still the same ship? Wait, it gets even weirder! What if a sneaky person collected all the old, rotting wood and rebuilt the exact same ship in another harbor? Now there are TWO ships! Which one is the real Ship of Theseus? Get ready to have your mind blown as Mira and Finn explore what makes you, YOU! You'll discover a shocking scientific fact: your human body replaces almost all its cells over the years! So, if you're made of totally new stuff, are you still the same person? Tune in to solve this incredible 2,000-year-old brain-bender!

Transcript

SPEAKER_00 0:00

Welcome to Philosophy is not boring by Kidopoly.com. I'm Mira. And I'm Finn. Hey Finn, I want you to try something. Have you ever looked at a picture of yourself as a really tiny baby? Like straight from the hospital?

SPEAKER_01 0:18

Oh yeah, my mum has them all over the house. I look like a little bald potato that just learned how to cry.

SPEAKER_00 0:24

Right. Well, here's a weird question for you. That bald potato didn't look like you, didn't talk like you, and definitely didn't know the things you know now. It couldn't ride a bike or tell jokes. So, are you actually the same person?

SPEAKER_01 0:43

Wait, of course I am. It's me! I mean, I grew up, but it's obviously still me.

SPEAKER_00 0:49

But what exactly makes it you? If literally almost everything about you has changed, what exactly is the thing that stayed the same?

SPEAKER_01 0:58

Oh, wait. That's actually kind of a hard question. Is it my brain? But my brain didn't know anything back then.

SPEAKER_00 1:07

Right? And to figure it out, we're going to look at one of the greatest puzzles in history. It's a 2,000-year-old brain bender about a hero, a harbour, and a ship. A ship?

SPEAKER_01 1:20

How is a ship going to tell me if I'm a bald potato or not?

SPEAKER_00 1:24

Stick with me, Finn. This is going to get weird. To get to the bottom of what makes you you, we have to travel way back in time to ancient Greece.

SPEAKER_01 1:34

Ooh, toga time! Who are we meeting? Are there monsters?

SPEAKER_00 1:39

Well, the monster part is already over when our story begins. We're talking about a famous legend that was recorded by an ancient Greek writer named Plutarch. It's about a mythical hero named Theseus.

SPEAKER_01 1:54

Theseus, the guy who defeated the Minotaur in the giant maze! I love that story.

SPEAKER_00 2:00

Exactly! And according to the legend, when Theseus finally sailed back home to Athens after his victory, the people were incredibly proud of him. So proud, they decided to keep his ship in the harbour forever to honour him.

SPEAKER_01 2:15

Oh, I get it. Like a floating museum. That's pretty cool. People could go visit the exact ship the hero sailed on.

SPEAKER_00 2:23

It was! But there was one major problem. Wood rots. Especially when it's just sitting in salty ocean water year after year.

SPEAKER_01 2:34

Oh no! The hero's historic ship is going to sink!

SPEAKER_00 2:38

That's a terrible museum. The people of Athens couldn't let that happen. So they came up with a maintenance plan. When one wooden plank got old and rotten, they took it out and carefully put a brand new, strong wooden plank in its exact place.

SPEAKER_01 2:55

Phew. Crisis averted. It's just getting a little repair. No big deal.

SPEAKER_00 3:00

That's what they thought too. But this leads to the big question Plutarch wrote about. If you replace one plank, it's obviously still the ship of Theseus, right?

SPEAKER_01 3:11

Yeah, obviously. It just has one new piece. If I get a flat tire on my bike and put a new one on, it's still my bike. Right.

SPEAKER_00 3:20

But picture this. Time goes by. Ten years later, they have to replace the tall mast. Then they have to replace the deck because it's getting squeaky. Then all the oars.

SPEAKER_01 3:32

Okay, they're just taking really good care of it. It's a lot of work, but it's worth it for the hero.

SPEAKER_00 3:38

Fast forward a hundred years, they have kept doing this over and over, and eventually, they have replaced every single piece of wood. Plank by plank, sail by sail. There is not one single splinter of the original ship left.

SPEAKER_01 3:54

Wait, hold on. Zero original pieces.

SPEAKER_00 3:58

Zero. Nothing Theseus actually touched is still there. And here is Plutarch's famous puzzle. Is it still the ship of Theseus?

SPEAKER_01 4:08

Oh, wait. Huh. If there's literally none of the original wood left, how can it possibly be the original ship?

SPEAKER_00 4:16

Well, the people of Athens would say, look at it! It's sitting in the exact same spot. It has the exact same shape. It has the exact same purpose. Of course it's the same ship.

SPEAKER_01 4:28

I guess so. I mean, it didn't suddenly become a completely different boat. But if I build a totally new bike out of entirely new parts in my garage, it's a new bike. It's not my old bike just because it looks like it.

SPEAKER_00 4:43

Some ancient philosophers totally agreed with you. They argued that the stuff a thing is made of, its physical matter, is what makes it real. If the matter changes entirely, it has to be a new ship.

SPEAKER_01 4:57

This is making my brain feel all squiggly. It is the same ship, but it's also completely different stuff.

SPEAKER_00 5:04

Then hold on tight, because a philosopher named Thomas Hobbs came along hundreds of years later and made this puzzle even weirder.

SPEAKER_01 5:13

Weirder? How can it get any weirder than a ship that completely replaces itself? Imagine this.

SPEAKER_00 5:19

What if there was a guy sneaking around the harbour every night, collecting all those old rotten planks they were throwing away?

SPEAKER_01 5:27

Haha, why would anyone do that? That's just a pile of wet, smelly wood. Gross!

SPEAKER_00 5:33

Because he has a secret plan. Over the years, he takes all those original rotting pieces, cleans them up, and carefully builds the ship again in a completely different harbour. Wait, what? So now there are two ships? Yes, think about it. Ship A is in the original harbour, made of totally new wood, but it never stopped functioning as a ship. Ship B is in the new harbour, perfectly reassembled out of the exact original wood Theseus actually touched.

SPEAKER_01 6:06

Oh my goodness, that's that's messing with my head. Here is Thomas Hobbes' big twist. Which one is the real ship of Theseus? It has to be Ship B, because it literally has the hero's actual wood. That's the stuff he sailed on.

SPEAKER_00 6:23

But wait, ship A is the one the whole town has been visiting and polishing every single day for a hundred years. They never even noticed a break in its history. Ship B was just a pile of trash for decades.

SPEAKER_01 6:37

Oh man. I don't know what I think anymore. They can't both be the one and only original ship of Theseus. That breaks the rules of math.

SPEAKER_00 6:46

Exactly. And philosophers have argued about this for over 2,000 years, and nobody has actually proven a final answer. It just depends on what you think matters more. What a thing is physically made of, or the continuous pattern of how it exists over time.

SPEAKER_01 7:04

Okay, I love a good puzzle, but what does a floating museum from ancient Greece have to do with me? I'm not a wooden boat. Well, remember that picture of you as a little bald baby potato? Oh yeah, the baby potato! Wait, are you saying I'm the ship? In a way, yes.

SPEAKER_00 7:23

Your body is constantly doing exactly what the Athenians did to the ship. Over the years, almost every cell in your body naturally dies and gets replaced by new cells.

SPEAKER_01 7:34

Wait, really? So my skin and stuff is new?

SPEAKER_00 7:38

Everything. Your skin, your bones, your blood, your body is constantly rebuilding itself. Over the span of about seven to ten years, your body replaces the vast majority of its physical parts.

SPEAKER_01 7:51

That's kind of scary to think about. If I'm not made of the same stuff I was made of when I was seven, am I even me? Did the old me disappear?

SPEAKER_00 8:00

I know, it feels a little spooky to realise that, but it's actually an amazing thing to wonder about. Some philosophers think this means you aren't just a collection of specific physical parts. They suggest you are the continuous pattern, the memories, the thoughts and the feelings that keep going even while your cells change.

SPEAKER_01 8:22

Oh, I really like that idea. So even if my planks get replaced all the time, I can still be the captain steering the ship. The story keeps going.

SPEAKER_00 8:32

Exactly. And here's a mind-bending fun fact. This puzzle is so famous that the ship of Theseus has been used in everything from comic books about robots to science fiction movies about teleporting, and even by scientists trying to understand human identity. Alright, Finn, it's quiz time! Let's see if your brand new brain cells remember everything we just talked about.

SPEAKER_01 8:55

Okay, I'm ready. Captain Finn is steering the ship.

SPEAKER_00 8:59

First question. Who was the famous ancient Greek hero who originally owned the ship? Next one. Which ancient writer recorded this famous puzzle about the wooden planks? Question 3. Who was the philosopher that added the twist hundreds of years later by building a second ship? Here's number four. In that famous twist, what did they do with the old rotten planks they took out of the water? Last question. According to science, what happens to the vast majority of the cells in your human body over the course of a few years? Great job! Let's see how you did. The first answer is the legendary hero was Theseus. For question two, the ancient writer who originally recorded it was Plutarch. Number three, the philosopher who added the second ship twist was Thomas Hobbes. Question four, they secretly gathered all the old planks and built a second ship out of them. And the final answer is, your cells slowly get replaced by entirely new ones, just like the ship.

SPEAKER_01 10:26

That is seriously mind-blowing. I am going to look in the mirror totally differently now. Am I the original Finn? Am I Finn 2.0?

SPEAKER_00 10:37

Just remember, you're still you, even if you're a newly upgraded version with different cells. It's completely safe and fun to just wonder about your continuous pattern. The absolute best version of the pattern. If you loved bending your brain with us today, please take a second to leave us a five-star review. It helps other kids find the show and join the conversation. Just scroll down in your podcast app and tap the five stars.

SPEAKER_01 11:04

Oh, and don't forget to check out our site kidopoly.com. We have tons of fun learning games and cool activities there to keep exploring big ideas.

SPEAKER_00 11:13

And if you want a shout out on the show, or just want to tell us what you think makes you you, email us at hello at kidopoly.com. We'd love to hear your thoughts on the two ships.

SPEAKER_01 11:25

See you next time on Philosophy is not boring. Bye everyone.