We spent most of our time talking through Williams’s argument about body switching.
At the very end, I described the last point he made, that personal identity is different than the identity of other things.
Williams presents a series of cases that involve two things:
The question he asks is whether someone who knew that the psychological changes were going to precede the torture would, for that reason, lose any reason to anticipate feeling the pain of torture.
Williams himself thinks the answer is “no” for each step on p. 172. The various psychological changes are changes in the person’s qualities but they do not make for a change in the numerical identity of the person. Poor Mr. A faces the prospect of an operation that will make him think and act like a different person followed by torture. He will emerge qualitatively different but numerically the same. The proof of this, according to Williams, is that he can anticipate feeling the pain of the torture. That shows that he will survive the psychological changes. Since that is how he sees it, Williams doubts Locke’s stories about body-switching.
A significant number of us disagreed with Williams, however. So we talked about exactly why the psychological changes involved at one stage of the experiment might be thought to be fatal to Mr. A, such that it wouldn’t be A who feels the pain at the end. I think it’s fair to say that there were two chief sources of resistance. Patrick, Josh, and Ian thought that the elimination of A’s character is what would remove A from the scene (roughly Williams’s second stage); Kai took a rather stricter line at the first stage.
The next big leap came at the sixth stage, where a large majority thought A would switch to B’s body. If that’s what you thought, you should think about why the sixth stage is so significant. The changes to A’s body are exactly the same as they are in the fifth stage. So why does the addition of B to the story make all the difference between A staying with the A-body and A moving to the B-body?
Williams arranges his cases on a spectrum. The challenge is to say why the difference between one step and another would be significant: if A would not die in, say stage two, why would the additional changes in stage three be fatal? The thought is that there is no satisfying way of distinguishing one stage from the next: either A dies at the first stage (amnesia) or A survives in the A-body in every stage.
One natural reaction to this style of reasoning is to say that there are points on the spectrum where there is no determinate answer to the question “would that be A?” or, if you like, “would A survive that change?”
That is the way we handle lots of different identity questions. Suppose you replace the battery in my watch. Is it the same watch? Sure. What about the glass covering? Again, it would be the same watch, just with a new crystal. If I took it apart, threw away all the parts, and made a watch out of new parts, I would pretty clearly have a new watch; the old one would be gone. But what if I replaced 40% of the parts? Would it be the same or different? 50%? 60%? For some of these intermediate cases, most of us throw up our hands: there’s no saying whether it’s a new watch or the same old one. There is just a watch that has 60% of the old parts and 40% of the new parts and there is nothing else to say about it.
The Ship of Theseus is similar. We can say what happened to the original planks of the ship and what happened to the replacement parts. But there is simply no saying exactly which ship is the same as the original.
We treat questions about the identity of watches as sometimes having indeterminate answers. That means there can be cases where there is no yes or no answer to the question “is it the same X?”
People, according to Williams, are different. There is no in-between state where the person is sort of there but sort of not there. So, for instance, either A feels the torture or A does not.
That is something that our next author, Parfit, will dispute. Parfit will maintain that it is possible for me to survive into the future even if no one in the future will be the same person as me.