Ship of Theseus

[drudman]

Theseus returns from Crete, and to honor his voyage, the Greeks haul that joint onto land and preserve it. For centuries they repair and replace the wooden ship's parts as they rot.

Is the ship that sits there today the ship of Theseus?

And then, what if they kept all of the rotted wood in a warehouse, and brought it back out now and reconstructed the ship next to the repaired and maintained one. Which ship is the ship of Theseus?

[Cerril]

Reminds me of the prologue to a story, which is obviously inspired by the same thing. It's funny enough I'll throw it here:

Let's say you have an ax. The kind that you could use, in a pinch, to hack a man's head off. And let's say that very situation comes up and for some very solid reasons you behead a man. On the follow-through, though, the handle of the ax snaps in half in a spray of splinters. So the next day you take it to the ax store down the block and get a new handle, fabricating a story for the guy behind the counter and explaining away the reddish dark stains as barbeque sauce.

Now, that next spring you find in your garage a creature that looks like a cross-bred badger and anaconda. A badgerconda. And so you grab your trusty ax and chop off one of the beast's heads, but in the process the blade of the ax strikes the concrete floor and shatters.

This means another trip to McMillan & Sons Ax Mart. As soon as you get home with your newly-headed ax, though, you meet the reanimated body of the guy you beheaded last year. He's also got a new head attached and it's wearing that unique expression of "you're the man who killed me last Spring" resentment that one so rarely encounters in everyday life.

You brandish your ax. He takes a long look at the weapon with his squishy, rotting eyes and in a gargly voice he screams, "that's the same ax that slayed me!"

Is he right?

[Cerril]

Anyway, so that was just for fun. I like that question though, it's an interesting semantics discussion.

I'd tend to say that our common usage of identity would have to say that the 'new' ship is the Ship of Theseus, in the same way that I am still me even as my parts and molecules are replaced bit by bit year after year. If I lose a toenail or scrape off some skin it's no longer part of me, no more than an organ transplant remains part of the original person (except perhaps in some bad movies). So the ruined ship built from cast-off parts would no longer be the Ship of Theseus, but a ship built from parts which were once a part of the Ship.

[Zeno]

The body regenerates itself through a series of biological processes (physical-chemical) whereas a ship, being inanimate, cannot do so. So the analogy is somewhat tipsy.

Can there be only one ideal Ship of Theseus, the first one, the one used and then abandon?

-Zeno

[Cerril]

Somewhat inappropriate, but our concept of identity doesn't tend to differentiate between those things. We say that a building is the same as it was ten or a hundred years ago despite repairs and improvements and maybe redecoration. Likewise a car doesn't become a different car when we get the oil changed, or even parts replaced (even external ones).

Now I understand the question is 'but is it -really- the same ship' and of course it's not quite the same ship of Theseus (that would be clear if we replaced the wood with metal, instead of more wood), but the other route would be to say that it's no longer the Ship of Theseus pretty much the moment after it's identified as the Ship, since some little part will have sloughed off. Third, you could say that 'it is mostly the Ship of Theseus,' or 'it is half of the Ship of Theseus' as you replace progressively more.

If you don't accept any of those you get the heap problem, where you have to decide at what point a thing is no longer a thing but in fact something else due to gradual changes.

But since it -is- a question of semantics, I would still say that no matter how much gets replaced, if the new parts are roughly similar to the old (i.e. wood of similar dimensions) then it remains the Ship throughout, and almost anyone would identify it as such.

[Girchuck]

The ship is also regenerating itself through a series of biological processes. They happen to involve people who are constantly updating the ship. If the Greeks forget about the ship and it falls apart, there will be no ship at all. Since it is the people who maintain the ship, whatever they want to call the ship of Theseus will be it.