DE Weekly: Identity, Plutarch, & the Ship of Theseus
Below is an archived email originally sent on March 31, 2025.
Identity, Plutarch, & the Ship of Theseus
Last week, I wrote about how certain stories and writings permeate the boundaries of their genres and allow us to apply an existentialist critique of them. Another such story we’ll discuss today is the “Ship of Theseus”.
Like the Allegory of the Cave from last week, you might have heard of this popular thought experiment before. Often viewed as a paradox, this story was popularized by Plutarch, a Greek philosopher in the Roman Empire who is most famous for his biographies.
The Ship of Theseus comes from Plutarch’s Life of Theseus, telling the story of the mythical founder and ruler of Athens.
It goes like this…
Theseus and his crew returned from a voyage to Crete on a ship with thirty oars, preserved by the Athenians over the ages, who disposed of the old planks once they decayed, and replaced them with new, stronger planks.
Over time, every piece of the ship was replaced in some fashion, with each plank of the hull being a new and different one that it had been when Theseus sailed on it.
The question: Is it the same ship?
One could contend that, yes, it is the same ship. You could also contend that it is not the same ship, but a different one entirely.
One side says the ship merely underwent necessary maintenance and upkeep over time, while another says the ship––bearing none of its original timber––is no longer the same ship at all.
Thomas Hobbes, the seventeenth century English philosopher, threw a nice spin on the thought experiment in his own right.
Hobbes questioned what would happen if all the original planks that were discarded from the original ship were assembled and used to build a second ship.
Would this be a different ship? Or would it now be the original ship, with the newer ship being a different ship? Maybe neither ship would be the real one.
People have come up with all sorts of answers, so I encourage you to think about it and find one to your liking.
As for now, same as always, I try to look through the lens of existentialism to see what can be gleaned from this paradox as it applies to our lives today.
Let’s use the question of identity for our existentialist foray into this thought experiment.
For the existentialists, identity is funny. On the one hand, it constitutes who you are (or who you see yourself to be), but on the other hand, it’s not a fixed entity at all.
Instead, it’s looked at as a process––one that changes over time, as we continue our march toward a life of meaning.
In a way, our identity is our essence. And, as articulated by Jean-Paul Sartre, it is our existence that precedes our essence. So no matter how our essence changes, we still have the fact that we existed and exist now––as ourselves.
We are born into existence, but we play at “becoming” from thereon out. In other words, we work for our essence, we choose our essence, and we construct our identity and negotiate it with the world in the way we choose to navigate it.
This is what Sartre was hinting at when he said, “You are -- your life, and nothing else.”
In existentialism, identity is not static. It is a project––a continual process of becoming––perhaps only cemented when we die. But, even then, those who remember us carry on our identities in the way they discuss us and honor our legacies.
Aristotle was familiar with the concept of essence long before any of the existentialists were. Aristotle himself applied this concept to the Ship of Theseus problem.
He argued that the ship’s essence is what makes it what it is. Not the materials or its design, but the idea of it.
For Aristotle, even if every single plank from the original ship was replaced, it would still be the same ship. After all, its essence hadn’t changed at all, just the materials.
One of the most apt solutions to the Ship of Theseus paradox comes to us from the Greek philosopher Heraclitus.
Heraclitus was quoted using the example of a river, saying, “upon those who step into the same rivers, different and again different waters flow”.
I think I like this solution best of all. It’s the same for identity, too.
The water molecules in the river change by the minute, but the river remains the same river.
The planks of the ship may be replaced, but the ship keeps its name and its essence.
I evolve and mature and change my appearance as I grow older, but I remain the same man.
Perhaps this paradox was solved millennia ago, after all. Or was it?
“No man ever steps in the same river twice, for it’s not the same river and he’s not the same man.” –– Heraclitus
Thanks for reading.
Sincerely,
Brandon J. Seltenrich
P.S.––
If there’s any other thought experiment you’d like to see me give the existentialist treatment to, from the Ancient Greeks or otherwise, let me know here. I love writing stuff like this and I’d be happy to do more of it.
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