This argument doesn't really make sense to me, sorry. It might be getting philosophical, but I think you'd be nearer to the matter if you were going to argue about what makes a specific ship that specific ship. For example, I can make a new ship that is exactly the same as the ship that sailed in 1912, even making it out of the same type of inferior steel and iron, but the real RMS Titanic is resting on the ocean floor, what's left of her. Likewise, people actually do argue about things like fictional characters being "real" or not. Saavik, for example (Kristy Alley vs. Robin Curtis). I even get into it myself with Kei and Yuri from Dirty Pair, as I reject the versions from Dirty Pair Flash. Kind of the same thing with nuTrek as far as rejecting the newer shows and movies. As for the Ship of Theseus argument, it's ironic in that I'm most familiar with it through the themes explored in Ghost in the Shell and its various adaptations. How much of a human can be replaced and still be human? In the 1995 movie, only a few brain cells of the person Motoko Kusanagi was remained. In Stand Alone Complex it was her entire brain. I'd actually argue that the brain is the only organ that can't be replaced while still remaining the same person. Deep Space Nine actually explored that a bit, too, but there's real historical examples of changes in personality and the like resulting from injuries to the brain, like a guy who managed to survive being impaled through the head but was a different person afterwards. The other side of this question in GitS concerns AI: as AI becomes more and more advanced, it may become difficult to distinguish it from a living person. At what point does an AI become a person, if ever?