The Ship of Theseus

One of the projects I am working on is the "restoration" of the Tregoning Skiff. I put restoration in quotes as the only original piece on the boat is the keel. There was some discussion as to what qualifies as a restoration and what is really a new boat. I remembered from my mythology class in college that there was a well known paradox that deals exactly with this question.

The ship of Theseus, also known as Theseus' paradox, is a thought experiment that raises the question of whether an object which has had all of its components replaced remains fundamentally the same object. The paradox is most notably recorded by Plutarch in Life of Theseus from the late first century. Plutarch asked whether a ship which was restored by replacing each and every one of its wooden parts remained the same ship.

"The ship wherein Theseus and the youth of Athens returned from Crete had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their places, in so much that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same." —Plutarch, Theseus

Plutarch thus questions whether the ship would remain the same if it were entirely replaced, piece by piece. Centuries later, the philosopher Thomas Hobbes introduced a further puzzle, wondering what would happen if the original planks were gathered up after they were replaced, and used to build a second ship. Hobbes asked which ship, if either, would be considered the original Ship of Theseus.