by Martin Davie, Christian Today
In Greek legend, Theseus, the King of Athens, rescued the children of Athens from King Minos of Crete after slaying the Minotaur. He then escaped from Crete on a ship heading to Delos. This ship was preserved at Athens and taken on an annual pilgrimage to Delos to honour Apollos.
As time went on, more and more bits of the original ship were replaced as they decayed. This raised a question among ancient philosophers which has come to be known as the ‘Theseus paradox.’ If a stage was reached when all the pieces of the original ship were thus replaced was the current ship still the Ship of Theseus? If not, at what point did the original ship cease to exist?
The discussion about this issue was first noted by the Greek writer Plutarch in his Life of Theseus. Plutarch writes: ‘The ship on which Theseus sailed with the youths and returned in safety, the thirty-oared galley, was preserved by the Athenians down to the time of Demetrius Phalereus. They took away the old timbers from time to time, and put new and sound ones in their places, so that the vessel became a standing illustration for the philosophers in the mooted question of growth, some declaring that it remained the same, others that it was not the same vessel.’
Philosophers today still discuss the Theseus paradox, namely, how much can something change and still retain its identity? Philosophers differ on this point, but the answer seems to be that identity can be said to persist in the face of change if there is some essential form of continuity.
Thus, in the case of Theseus’ ship, the fact of its having a continuous history even while a growing number of its parts were replaced means that it could be said to be the same ship. In a similar way a human being can be said to be the same person although billions of cells in their bodies are replaced every day.
The issue of continuity and change is also raised by the study of Christian doctrine. This is because Christians have historically held two convictions concerning Christian doctrine. The first is that the content of Christian doctrine is unchanging. The second is that Christian doctrine rightly develops.