In the 1st century AD, Plutarch wrote of the ‘ship of Theseus’, a well-known philosophical paradox, revived by Thomas Hobbes and rearticulated over time by philosophers and teachers. The story provides a basis to discuss identity.

In Plutarch's story, Theseus was a hero who had sailed the oceans with great success. The people of Athens kept his ship in a harbour, as a museum piece, to honour his triumphs and to preserve it for future generations. To maintain the ship, they replaced old, broken pieces with fresh, new pieces. Eventually all the pieces of the ship were replaced, and the question became, ‘Is this still Theseus’ ship?’ According to Plutarch, half the philosophers of the day said it was, and the other half said it wasn’t.

In the 17th century, Thomas Hobbes resurrected the paradox of Theseus’ ship. He imagined a young sailor, too poor to buy his own ship, who took the old pieces and stowed them away. Eventually the young sailor had enough pieces to make his own ship out of the old pieces of Theseus’ ship. So now there were two ships. And the question became, ‘Which ship is Theseus’ ship?’

The story of Theseus’ ship, and the questions it raises, provided the basis of the opening philosophical discussion for an ‘Introduction to Philosophy’ class I delivered in two prisons in England during 2014 and 2015.