Tuesday, July 28, 2009

Blessing Theseus's Ship

I took a philosophy of mind class some time ago, and one of the things they discussed was Theseus's Paradox.

Let's say we have a wooden ship. We replace each plank on the ship, one by one, until none of the original planks are part of the ship. Is it the same ship now? If not, when did it stop being the same ship? Now we take all those extra planks and put them together in the exact same way they were before. Are either of these ships the same ship as before, and which one?

This was the sort of question which made me hate philosophy.

However, Zeno Ferox just gave me an idea to solve this paradox once and for all. Supposedly, you only need to bless a rosary once--further blessings do not increase its blessedness. And if you replace, say, 20% of the beads, you don't really need to bless it again, because the blessing is integral to the rosary itself. Aha, so we know that it's still the same rosary even when 20% is replaced!

So, here's the experiment:
  1. Bless a rosary.
  2. Replace one bead.
  3. Ask the priest whether it is still blessed.
  4. Repeat steps 2 and 3 until all beads are replaced.
  5. Use the original beads to make another rosary.
  6. Ask the priest if the rosary is blessed.
There are a few difficulties in this experiment. First of all, it must be double blinded. The priests can't be given any indication how many beads were replaced. Second of all, I'm assuming that the priests can tell whether an object is blessed or not. Uh, they can tell, right? They don't need to be perfect, of course. We'll just repeat the experiment with a hundred different rosaries and average out the results. And we might as well toss in a control group of unblessed rosaries while we're at it.

I wouldn't have thought Theseus's Paradox to be a scientific question, but clearly I was wrong.


Larry H. said...

I think Theseus's Paradox is a perfect example of a Wittgensteinian pseudo-problem.

Issues such as Theseus's ship have some value in identifying and studying ambiguities in our thinking; the error of Theseus's ship is considering it an actual paradox of objective truth. There is no objective truth about whether the ship always remains the same or somewhere becomes a "different" ship.

Hell, I don't even know whether its the "same" electron after a moving to a lower energy state. (IIRC, some features of QM include the mathematical assumption that all quanta of the same type are inherently deeply indistinguishable.)

The problem, though, is that we can determine that our thinking about identity (and other concepts) is fuzzy, but so what? What's inherently wrong with fuzzy? There are some circumstances where we need to be precise and unequivocal, but do we need to be precise and unequivocal about Theseus's ship, heaps of sand, the ontological status of holes and the value of potatoes?

A large part of the value of natural language, I think, is precisely its ambiguity and equivocality. These features allow us to more easily creatively transfer our intuitions from one domain to another. We do have the facility (e.g. mathematics) to speak precisely and unequivocally when we need to do so.

There is a strain of puritanism and sanctimony in the philosophical profession: the messiness and ambiguity of ordinary life and ordinary language seems to cause no small few philosophers almost physical pain, and they're often entirely un-shy about expressing their contempt and disdain for ordinary life and thought.

Secret Squïrrel said...

I don't see Theseus' ship as paradoxical at all. As soon as you replace one plank (or one nail, piece of caulk, etc), it is no longer the same ship. Sure, it's very nearly the same, almost exactly, but not.

If you were to completely replace all of the parts of the ship and then reassemble the replaced parts in exactly the same configuration it still won't be the same, as the planks have spent some of their time in a pile in a shed - they have different histories from what they would've had.

This poses an interesting question regarding teleportation devices, which I'm just going to pretend actually exist. I'm not talking about the Star Trek/Blake's Seven type that have a single station that can deposit and retrieve payload pretty much wherever, but the type that can transmit a person from one booth to another like in "The Fly".

Assuming that these work by converting you into a stream of subatomic particles and reassembling you at the other end, any person who uses one of these is killed in the most absolute fashion (complete disintegration) before a facsimile is constructed at the other end.

Although this facsimile will look and behave exactly like the person who stepped in at the start, is it really them?; i.e. is it the same person? I lean toward "yes" if they can't be told apart by any means.

Furthermore, in order for the machine to correctly reconstruct the person, it must have a complete map of every single particle of which they are made (Uncertainty notwithstanding). Could the person's mind be said to be also within the machine? And could this map then be used to construct a second (or millionth) copy of the same person from a suitable batch of ingredients?