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The Ship of Theseus: A Thought Paradox

Who Are You?

Who are you? Which “you” represents your identity? Is it your 5 year old self, your current self, or perhaps even some future version of you? How can we truly tell what defines you as a person? The question of “what is identity” has been asked, in different variations, over many years. But it all originated with one Ancient Greek philosopher: Plutarch.

Plutarch was known for his many works, including his books Parallel Lives and Moralia, but today we are going to be talking about a thought experiment he discussed that would puzzle philosophers for more than 1,000 years.

The Ship of Theseus

In this thought puzzle, there is a “ship of Theseus”. Theseus was a hero of Greek mythology who also supposedly founded Athens.

Anyways, he had a ship. Since it was such a special ship, the Athenians wanted to preserve it. So, for every plank on the ship that started decaying, they replaced it with a new plank.

Let's say they replace one plank a year. So, eventually, after a certain amount of time, there will be no more original planks on the ship. Is it still considered the “ship of Theseus”? This ship became a debate amongst philosophers, one side arguing it was the same ship, the other side saying it wasn’t.

Approaches Taken

The first side of this debate considered it to still be the ship of Theseus because the change happened so gradually over time. Let’s call this ship (the one with the new planks) Ship 1. So, is there really a single point in time where Ship 1 loses its identity as the ship of Theseus? If the original ship only had one replaced plank, you would still consider it the same exact ship. If we consider one plank not changing anything, then technically, the ship doesn’t change at all.

But, going against this logic, could it suddenly become a new ship once, for example, 50% of the planks have been replaced? Or when 75% of the ship is now made up of completely different parts, is it still the original ship?

Another approach taken is mereological essentialism, which is the belief that an object's parts are essential. This means that a thing is basically the sum of all its parts, and nothing more. So if it were to lose a part, it wouldn’t be that same thing anymore. Using this logic, once the first plank on Ship 1 was replaced, it was no longer the ship of Theseus.

However, there is a small issue with this logic. Because everything gradually changes over time, nothing could ever be the exact same thing as it was before. So some people argue that saying something is not the same as before is more accurate than calling them two completely different objects. For example, would you call yourself a completely different person after losing a baby tooth? So, mereological essentialists might say that the original ship and Ship 1 bear enough of a resemblance to be called the same ship, however, they are technically not.

Some argue that the ship remains the ship of Theseus until a certain number of planks are replaced. But why does one certain plank determine whether or not it remains this ship? What if the ship consisted of 1,000 planks and 501 planks were replaced? You could substitute this for any number and still ask why.

And finally, is it different if it's a quick change rather than a gradual one? What if the whole process somehow took 10 seconds instead of 10 years? If, all of a sudden, all the planks were replaced, you’d call it a different ship because of how drastic the change was in such a short period of time. But, if you used the earlier example, which was one plank a year, you would consider it the same ship because of how slow it was.

What if There was Another Scenario?

Then, another philosopher named Thomas Hobbes came up with an addition to this puzzle. What if the old parts that we took out were collected, and made into a new ship exactly like Ship 1? Let's call this ship Ship 2 (the new one made out of the decaying parts). Which ship, if any, is the Ship of Theseus?

People have thought that because Ship 1 was derived from the Ship of Theseus, that Ship 1 is the original ship. Even though the material is now different, Ship 1 has the same foundation, the same design, the same structure, and the same name, so it remains the original ship.

On the other hand, the second argument states that a ship is its parts, so technically Ship 2 is the ship of Theseus. Before, we assumed the old decayed parts were thrown away, but now that they are actually reformed to make a whole new ship, could you now consider Ship 2 the “original” ship?

So What Makes Us... "Us"?

There are so many possibilities for this puzzle, which is why philosophers see philosophy as not just a practice, but as a way of life. So how does the ship of Theseus relate to our everyday lives?

We are always growing, and thus, our bodies are always changing. After switching so many things about ourselves, changing our personalities, dying our hair, we still remain the same person.

Although seemingly unjustifiable, we always stay the same, no matter how much we change. So what is it that keeps us tethered to our names? If it's not our appearance, our personality, our actions, or even our way of thinking, then what could it be?


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  2. Levin, Noah. “Ship of Theseus.” Philosophical Thought, Tulsa Community College, 13 Aug. 2021,

  3. Worely, Peter. “The Ship of Theseus.” The Philosophy Foundation - the Ship of Theseus, 2021,

  4. Popova, Maria. “The Ship of Theseus: A Brilliant Ancient Thought Experiment Exploring What Makes You You.” Brain Pickings, 18 Jan. 2021,

  5. N, A. “The 'Ship Of Theseus' Problem [Illustrated].” YouTube, YouTube, 19 June 2020,

  6. Cohen, Marc. “Identity, Persistence, and the Ship of Theseus.” Washington Faculty, 2004,

  7. Williams, Bethany. “The Ship Of Theseus Thought Experiment.” TheCollector, 29 June 2021,

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  10. TEDEducation, Amy Adkins. “Who Am I? A Philosophical Inquiry - Amy Adkins.” YouTube, YouTube, 11 Aug. 2015,

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