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The ship Theseus

This is not what Ray North had bargained for. As an international master criminal he prided himself on being able to get the job done. His latest client had demanded that he steal the famous yacht Theseus, the vessel from which British newspaper magnate Lucas Grub had thrown himself to his death and which more recently had been the scene of the murder of LA rapper Daddy Iced Tea.

But here he was in the dry dock where the boat had just finished being repaired, confronted by two seemingly identical yachts. North turned to the security man, who was being held at gunpoint by one of his cronies.

'If you want to live, you'd better tell me which one of these is the real Theseus: demanded Ray.

'That kinda depends,' came the nervous reply. 'You see, when we started to repair the ship, we needed to replace lots of parts. Only, we kept all the old parts. But as the work progressed, we ended up replacing virtually everything. When we had finished, some of the guys thought it would be good to use all the old parts to reconstruct another version of the ship. So that's what we've got. On the left, the Theseus repaired with new parts and on the right, the Theseus restored from old parts.' 'But which one is the genuine Theseus?' demanded Ray. 'I've told you all I know!' screamed the guard, as the crony tightened his grip. Ray scratched his head and started to think about how he could get away with both…


Philosophy concerns itself with the questions that still remain unanswered once all the facts have been collected. In this scenario, Ray knows all the relevant facts about the two boats. Yet the answer to his question remains mysterious.

For some people, it is intuitively obvious which is the genuine Theseus. But which answer they give will depend on how you tell the story. If Ray were a detective looking to gather forensic evidence about the deaths of Lucas Grub and Daddy Iced Tea, it would seem pretty obvious that he would count the reconstructed Theseus as the genuine article. He might reach the same conclusion if he were a collector of objects with a historical significance. However, if there were an ownership dispute, the repaired Theseus would be counted as the original. That is the boat the owner is entitled to sail away. And if you were to have placed a time-delay camera in the dry dock and followed the progress of the works, you would have seen the boat that came in gradually being worked on with the repaired version as the end result, while the restored one would have only later started to emerge beside it. The repaired ship thus has a continuity of existence which the restored one does not.

You might then think that which is the 'genuine' Theseus is not a question with a single answer. It all depends on what your interest in the boat is. But this answer may have disturbing consequences. For are not people rather like Theseus? As we go through life, the cells in our body continually die and are replaced. Our thoughts too change, so that littl of what was in our heads when we were ten years old remains when we are twenty, and these thoughts, memories, convictions and disposi- tions are in turn replaced as we grow older. Are we then to say that there is no right answer as to whether we are the same people who we were many years ago and that it just depends on what our interest in ourselves is? If the identity of Theseus is not a factual matter, then can there be a fact about the identity of anything that gradually changes over time, human beings included?

from The Pig Who Wants to be Eaten by Juian Baggini (page 31)

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