What makes something the same object over time, even if all of its parts are replaced?
This might sound like a strange question, but itโs one of the oldest and most interesting puzzles in philosophy. And we still ask similar questions all the time: about identity, technology, artificial intelligence, and ourselves.
If you change over time, your personality, your body, your memoriesโฆ are you still the same you?
In todayโs episode of Thinking in English, weโre going to explore this fascinating idea through one of historyโs most famous thought experiments: the Ship of Theseus.
As always, this episode is designed to help you improve your English. Iโll introduce you to useful vocabulary, explain ideas clearly, and make you think more deeply in English.
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Vocabulary
- Thought experiment (n): A thought experiment helps philosophers imagine what would happen if one part of a situation changes.
- The Ship of Theseus is a famous thought experiment about identity and change.
- Identity (n): Your identity includes your name, personality, and the things that make you different from others.
- Changing your clothes doesnโt change your identity.
- Mythology (n): Mythology tells us stories about gods, heroes, and ancient events that explain a cultureโs beliefs.
- Greek mythology includes stories about Zeus, Hercules, and the Minotaur.
- Paradox (n): A paradox is a problem or statement that seems impossible but makes you think deeply.
- The Ship of Theseus creates a paradox because the ship changes, but we still call it the same.
- Continuity (n): Continuity means something stays connected or the same over time without interruption.
- The continuity of the company depends on keeping its values and customers over many years.
- Function (n): The function of a tool or machine is what it is used for or what it does.
- The function of a watch is to tell time.
A Real Life Example
Let me start with a real life example.
A few years ago I was watching a video on YouTube about watch repair.
I’ve been fascinated by Wristwatches for a few years. I like to learn about how they work, how they’re built, and how skilled watchmakers can take something old and broken and make it work like new again.
In the video, the watchmaker was restoring a beautiful vintage watch, but some parts of the watch were completely broken or too damaged to fix.
So he replaced them. He added a new glass cover, new hands, a new strap,[00:04:00] new springs and screws inside the movement, which is the parts that makes the watch work.
By the end of the repair the watch looked amazing. It worked perfectly. But many of its parts, maybe 25 to 50% were completely new. That made me wonder, is it still the same watch?
This leads us to an ancient question that philosophers have been debating for over 2000 years.
And it all goes back to a hero from Greek mythology: Theseus.โ
The Myth of Theseus
The myth of Theseus is a famous story that I’m sure many of you have heard before.
Theseus was a prince of Athens, but as a child he didn’t know he was royalty. He grew up far away from the city with his mother.
When he became a young man, he discovered the truth. That he was the son of the king and the rightful heir to the [00:05:00] throne of Athens.
At that time, Athens had a terrible problem. Every year, the city had to send seven boys and seven girls to the island of Crete.
Why? Because of a cruel agreement with King Minos of Crete.
These young people were sent into a dark and dangerous labyrinth. A huge maze built under the city. Inside the maze lived a terrifying monster. The Minotaur. The Minotaur was a creature that was half man and half bull. The Minotaur would eat the children and no one had ever escaped.
Theseus wanted to prove that he was brave and worthy of being king. So he volunteered to go to Crete and face the Minotaur.
Before he left, his father gave him two sets of sails, white sails and black [00:06:00] sails. Sails are the part of the ship that catches the wind. Theseus promised to return with white sails if he survived, and black sails if he died or failed.
Theseus and the other young Athenians boarded a ship and sailed to Crete. The ship they used is the famous Ship of Theseus
In Crete, something unexpected happened. Theseus, met a princess, the daughter of King Minos.
She fell in love with Theseus and wanted to help him. Secretly, she gave him a ball of thread and a sword.
Theseus used the sword to fight and kill the Minotaur, and he used the thread to find his way back out of the labyrinth. He saved the other children, escaped Crete and sailed back to Athens.
But on the way home, Theseus made a tragic mistake. He forgot to change the sails. [00:07:00] He arrived in Athens with black sails flying from the ship.
His father, the King, saw the black sails and believed his son had died. In his grief, the king jumped off a cliff into the sea.
Theseus became the new king of Athens. To honor his journey and his father’s death, the people of Athens kept the ship as a symbol of courage and heroism. They repaired it and protected it for many generations.
This legendary ship, the Ship of Theseus, is now at the center of a fascinating thought experiment.
What happens to something when you keep repairing it, replacing its parts, and changing it over time? Is it still the same?โ
Plutarch’s Puzzle
The earliest version of this thought experiment that I could find comes from the Greek writer and philosopher, Plutarch.
In his book, the Life of Theseus, [00:08:00] Plutarch described how the people of Athens took care of Theseus’s ship.
As the wooden planks began to rot or break, they replaced them one by one. First a board here, and then a beam there. Slowly, piece by piece, the ship was repaired.
Eventually, every single part of the ship had been replaced. None of the original wood remained. And this created a puzzle or a paradox.
Plutarch wrote;
“The ship wherein Theseus and the youth of Athens returned from Crete, had 30 oars, and was preserved by the Athenians. For they took away the old planks as they decayed, putting in new and stronger timber in their places. The 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.”
So [00:09:00] here’s the basic question.
Is this still the same ship of Theseus? If none of the original parts are left, can we still call it his ship? Or has it become something completely new?
This is not just about ships. The same question can be asked about anything, like the watch I mentioned earlier. If all of the parts are changed, is it still the same object?
We can also ask this about ourselves.
You are not made of the same cells you had as a child. Scientists say the human body replaces most of its cells every seven to 10 years. Your thoughts, your memories, even your personality change over time.
So are you still the same person you were 10 years ago?
Thomas Hobbes
More than a thousand years after Plutarch, the English philosopher Thomas Hobbes [00:10:00] added an extra layer to the ship of Theseus puzzle.He made the question even harder to answer.
Remember how the Athenians repaired the ship by replacing the old wooden parts with new ones.
Hobbes asked,
What if someone didn’t throw away the old parts? What if they saved every plank, nail and oar that had been removed?
Then imagine this. Someone takes those original parts, carefully repairs them and uses them to build a second ship. A ship made completely from the old original materials.
Now there are two ships.
The first ship in Athens has been repaired and maintained over time. It looks just like the original, but it’s made from completely new parts.
The second ship has been rebuilt using the actual old parts, the [00:11:00] ones Theseus really touched and used during his journey.
Which one is the real ship of Theseus? Is it the ship that has stayed in Athens, always being repaired and used, but with new parts? Or is it the one that has been rebuilt from the original historical materials, even if it hasn’t been used for years?
Some people say the repaired ship is the real one because it has continuity. It has a history of use and a connection to the city.
Others say the reconstructed ship is the true original because it contains the real materials Theseus once used.โ
The Paradox Beyond the Ship
I think the ship of Theseus thought experiment is actually a powerful way to think about modern life technology and who we are as people.
Think about a smartphone. Over time, you might replace the screen as it cracks, upgrade the battery, add a new [00:12:00] case, or even change the internal parts.
At what point does it stop being your original phone? Is it still your phone if none of the original parts are left?
Or what about a classic car? Some people restore old cars by replacing almost every part. New engines, new wheels, new paint, but they still call it the same car… is it?
Imagine a robot that slowly upgrades over time. It gets new arms, new processors, and even a new memory system. If it’s constantly changing and updating, is it still the same robot?
Let’s go even further. Think about culture. A country or a city changes its buildings, its language, and its traditions over time, but we still call it the same place.
Japan today is very different from Japan 1000 years ago. So why do we still call it [00:13:00] Japan? France today is completely different to the France from 1000 years ago. Britain today is completely different from the Britain 1000 years ago.
Are these still the same countries? Are these still the same places?
Or imagine a company that gets new employees, new owners, and even a new name. Is it still the same business?
The ship of Theseus helps us explore all of these situations. It makes us ask: What makes something the same over time? Is it the parts, the function, the name, the memories?โ
Solutions to the Problem!
Philosophers have tried to solve the Ship of Theseus problem.
First, there’s the ancient philosopher, Heraclitus. He tried to solve the issue by thinking about water.He wrote,
You can never step into the same river twice.
He meant that a river is always changing. The water [00:14:00] flows and is never exactly the same from one moment to the next. Yet we still call it the same river.
He thought that change is natural. Things stay the same, only because we give them a name and a meaning.
Other thinkers say what matters is continuity over time.It’s not the material parts that make something the same, but the continuous existence or function.
For example, a car that is repaired and maintained over many years is still the same car because it has a continuous use and history.
The same idea applies to people. We are the same person because our mind and memories continue even if our bodies change.
However, there is no single answer that everyone agrees on.โ
Final Thought
Now itโs time for your thoughts.
What do you think? Is something still the same if all its parts are replaced? Or does it become something new? Which ship would you choose as the real Ship of Theseus: the repaired one or the one rebuilt from the original parts?
And what about yourself? Are you the same person you were ten years ago? Why or why not?
Thinking about these questions in English is a great way to practice your language skills and to improve your ability to discuss complex ideas!
Leave a comment with your opinion on the Ship of Theseus!
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