Ship of Theseus and Personal Identity

In the Life of Theseus by Plutarch we read a story that harbor’s philosophical questions about personal identity(yes, that was a pun).  Theseus sailed his ship to Crete for a hostage rescue mission.  In the midst of his mission he fought and killed a Minotaur (a beast with the head of a bull and the body of a man).  After rescuing several Athenians from captivity he sailed back to Athens in his ship.  The event was so big that Theseus became an Athenian hero and was honored by the annual sailing of his ship.  This celebration went on for centuries.  As the ship became aged it became less sea worthy.  However, in order to keep the annual recognition of this great time in Athenian history Theseus’ ship was in a state of constant repair and up keep.  As planks aged and weathered they would be replaced.  As time went on some began to question if this was still Theseus ship; after all the planks that held it together had been removed and replaced several time over.  Moreover, if it is Theseus’ ship then by virtue of what does it remain to be Theseus’ ship.

To add a twist to the story, what if a second ship was built using the original planks of Theseus ship?  Lets say some enterprising harbor employee rummaged the trash bins after Theseus ship had been retrofitted with new planks.  He managed to keep all the original planks until he was able to build an entire replica of Theseus ship.  Would it be fair to call it a replica?  Wouldn’t it have more claim to being Theseus’ ship then the retrofitted ship?  This is just a question over man made objects asking us to consider the identity of things and how identity is established.  As complicated as this might be how much more complicated does it become when we speak of personal identity?  Does personal identity change?  What kinds of things influence change?  Obviously if I lost weight weight or started using dentures I would be qualitativly different but I would still maintain my identity.  The same would hold true about a heart transplant.  But, what about a brain transplant?

We probably cannot begin to answer these type of questions until we have established a concept of person from which to work from.  If you have one please leave it in the comments, I’d be interested to read it.