This, milord, is my family's axe. We have owned it for almost nine hundred years, see. Of course, sometimes it needed a new blade. And sometimes it has required a new handle, new designs on the metalwork, a little refreshing of the ornamentation . . . but is this not the nine hundred-year-old axe of my family? And because it has changed gently over time, it is still a pretty good axe, y'know. Pretty good.I mean, this is as nice a common sense defence of the piece, but in the context of the book, it is really excellent.*
Anyway, I planned just to post the above, until I was looking for the quotation and found it on a page about the Ship of Theseus. I knew the axe thing was an old philosophical question, but I didn't know the specifics, and now I do.
The Ship of Theseus - is it the same after all the bits are replaced? - is the Ur-formulation of this question (in the western canon, anyway). John Locke's example was to do with his socks (all his postulations rhymed with his name). The French have Jeannot's Knife. The American's have George Washington's axe and so do I. I wonder what I could get for it on the open market?
Because I am a moron, I had never really considered how this is analogous to the whole problem of stepping in the same river twice. It is also the root of some philosophical problems involving matter transference. Is a teleported thing the same thing? (I have never been the same since I teleported.)
*I have a long term plan to blog about Pratchett's books in chronological order. You must be thrilled about this.