About This Puzzle
The Greek writer Plutarch tells of the ship on which the hero Theseus returned to Athens. The Athenians kept it for centuries, pulling out planks as they rotted and fitting new timber in their place, until the ship became a standing example for philosophers arguing about things that grow and change.
Is it still the same ship? Almost everyone says yes after one new plank, and many hesitate by the last. Somewhere in between, if anywhere, the answer changes. This version lets you do the repairs yourself, one plank at a time, with the years ticking past, and asks you to put a finger on that moment.
Then it adds the second, sharper half of the puzzle. Every plank you took out has been kept in a shed. What happens when someone builds them back into a ship?
The Hobbes Twist
In the seventeenth century, Thomas Hobbes pushed the puzzle further. Suppose the discarded planks were kept and later put back together in their original order. Now there are two ships. One has sailed continuously, its history unbroken. The other is made of nothing but the original wood. If you had to hand "the ship of Theseus" back to Theseus, which would you give him?
Whatever you answered about the gradual repairs, the second ship tends to put pressure on it. That is why the game asks for your mark first and your choice second, and then checks whether the two agree.
The Four Answers
- The repaired ship: identity follows an unbroken history of use, place and repair, the way a river or a city stays itself while its parts change.
- The rebuilt ship: a thing is its material. Put the original parts back together and the original is back.
- Both: treat objects as stretched through time, and the two ships share one past before they fork, so each has an equal claim.
- Neither, really: once every fact about the planks is known, nothing is left to discover. "Same ship" is a label we apply when it is useful.
How To Play
- Tap or click a plank to replace it. Each repair moves the calendar forward a year or two.
- Or press Let the years pass and watch the repairs happen by themselves. Press it again to pause.
- Press It’s no longer the same ship the moment you believe it. If you never do, replace every plank and say it is still the same ship.
- Watch the shed become a second ship, choose which one is real, and read what your answer commits you to.
Frequently Asked Questions
What is the Ship of Theseus?
It is one of the oldest puzzles about identity. The Greek writer Plutarch described the ship of the hero Theseus being kept by the Athenians for centuries, with rotting planks replaced by new ones, until philosophers argued over whether it was still the same ship. If every part of something is replaced, gradually, is it still the same thing? And if not, when did it stop being?
What is the Hobbes twist?
The English philosopher Thomas Hobbes added a second ship. Suppose someone kept every discarded original plank and later reassembled them. Now there are two ships: one that was continuously used and repaired, and one made entirely of the original material. Both have a claim to be the ship of Theseus, and they cannot both be the one original ship.
Is there a right answer?
No agreed one. Philosophers have defended each of the four options in this game: that the repaired ship is the original, that the rebuilt one is, that both have an equal claim, and that the question has no deeper answer beyond how we choose to use words. The game tells you which of these your choice matches, and whether it fits with the moment you marked.
How do I play?
Tap or click planks to replace them, or let the years pass and they will be replaced for you. Each repair moves the calendar on. Press the mark button the moment you think it is no longer the same ship, or keep going to the last plank if you think it never stops being the same. After that, the discarded planks are rebuilt and you choose which ship is the real one.
Is my answer saved or compared with other people?
Your last mark and choice are kept in your own browser so the page can remind you next time, and nothing is uploaded. There is no comparison with other people's answers, because the page does not collect them.
What does this have to do with my body?
Quite a lot, though not in the way the popular claim suggests. The idea that every cell in your body is replaced every seven years is a myth. Some cells, like those lining your gut, are replaced within days, while most neurons in your cerebral cortex are never replaced and are as old as you are. The end of the game shows a few examples.
More Games & Tools
The Boiling Frog →
Another slow change: a number climbs in full view. How well were you really tracking it?
Your Ancestors →
Double back one generation at a time until the arithmetic stops making sense.
Human or Machine →
A different identity question: which sentences were written to sound like a machine?