Is it still the same ship?
If every plank of a ship is replaced, one at a time, is it still the same ship?
About 1,900 years ago, the Greek writer Plutarch told the story of the ship of Theseus. The people of Athens kept their hero’s ship for centuries, pulling out old planks as they rotted and putting in new ones.
Plutarch said philosophers used the ship as an example: some argued it stayed the same ship, and others that it didn’t.
In 1655, the English philosopher Thomas Hobbes added a twist. What if someone kept all the old planks and built them into a second ship? Which one would be Theseus’s?
The question has never quite gone away, because it’s also about people. Our bodies change, our memories change, our minds change. So what makes someone still themselves?