Julien Roger

VP Finance @ Humi
Founder @ Abletribe
Pretend Photographer

The Ship of Theseus

January 2020

I want to tell you about one of my favourite thought experiments. There are a few different versions of it with slightly different implications. This isn’t the original version, but I think it’s the most illustrative.

The Story

The story is about a ship sailed by Theseus, an ancient mythical king and founder of Athens.


Theseus fought and won so many battles at sea that when Theseus built his new ship for his next campaign, the Athenians came to the port to send him and his crew off. They declared that this ship was the ‘Ship of Theseus’.

After about a month at sea one of the wooden planks in the ship started to rot. Fortunately the crew had brought some extra wooden planks for repairs. The crew replaced the rotting plank and threw the old plank into the ocean. Everyone agreed it was still the Ship of Theseus.

After a few more months at sea a few more planks started to rot. They were replaced and thrown to the sea, and everyone still agreed that it was the Ship of Theseus.

Eventually after many many months at sea, all the planks in the ship had been replaced.


I want you to stop and think here for a second. Is this still the Ship of Theseus?

My gut says yes.

But hold on. Because things are about to get weird.

The Twist

When Theseus and his crew set sail, an Athenian also set sail in his scavenger boat. He collected all the rotten planks that the crew had thrown into the ocean and took them back to shore. When he got back, he put together all the planks in their original positions, rebuilding the Ship of Theseus while Theseus was still at sea.


Now there are two ships - one at sea with Theseus and his crew, and one on shore with the original planks from the Ship of Theseus that left port.

Think about this:

Which ship is the Ship of Theseus?

It’s not an obvious question.

Identity

There’s a common belief that your body replaces all its cells every 7 years. While it’s not true (different cells replace at different rates, with some cells like brain cells rarely ever replacing themselves) imagine that it was true.

The concept of ‘you’ is clearly separate from form. You’re more than the cells that make up your body.

Our understanding of identity is linked to our ability to develop a linear narrative. Story is how we understand the universe.

There was a big bang, stars formed, then earth, then life, then us.

We understand ourselves through narrative; resumes, biographies, epic poems. All are temporal descriptions of existence.