Theseus is the captain of a ship.
He is sent on a voyage that will take just over a year to complete.
Though out the voyage,
pieces of the ship begin to rot, and need to be replaced.
Theseus has his men remove each piece of wood as it rots,
and replace it with another.
By the time Theseus has returned to port,
his ship is composed of entirely new pieces of wood.
Is the ship the same ship that he originally departed with?
Let us also suppose, that during the voyage,
there is a following ship.
The following ship is a scavenger,
that retrieves the old pieces of wood as they are removed from Theseus' ship.
The scavenger than creates an entire ship from the old pieces.
Which than, would be Theseus' ship?