Williams thinks Locke’s cases went by too quickly. When you look at them more carefully, he thinks, it is not obvious at all that people can switch bodies. In particular, if you consider what it would be like to think about being involved in one of those cases yourself, you would not be so sure that Locke was right about them. At the end of his essay, Williams discusses what appears to be a unique feature of human beings. For most things, there need not be a determinate answer to questions about whether they survive some changes. Sometimes, there is no saying one way or the other. People seem to be different: I will either be alive or I will be dead.
What is this about?
This essay is going to be about a process whose result is that one person, A, acts in ways that seem to express the memories and character traits of another person, B, and vice versa. This is basically Locke’s example of the prince and the cobbler; see Locke §15.
These sorts of examples are commonly thought to involve body-switching: the A-person goes to the B-body and vice versa. Williams says that this description is “question-begging” (page 161, third line) What he means is that describing it as an example of body switching assumes what the example is supposed to show, namely, that the people have switched bodies. The point of this article is to raise questions about that.
Before getting to work, he raises two complications, but only to put them aside. First, you might have trouble believing that one person could switch into a vastly different body; Williams says he will assume that A and B are physically similar. Second, you might ask why it is obvious that the B-body person remembers what the A-person did and experienced as opposed to feeling, falsely, that he or she remembers. Williams says he will assume that the process he is discussing is as physically reliable as a normal brain is.
The experiment, round one
The experiment is the process that seems to lead to body switching (163). We start with two people, A and B. Each is told what is going to happen. At the end of the experiment, the B-body person will seem to have A’s memories and character traits and vice versa. Plus one of them is going to get $100,000 and the other is going to be tortured. Then the experimenter asks each of them to choose which body will get the money and which one will be tortured.
Suppose that A says “give the money to the B-body person” and B says “give the money to the A-body person.” Suppose also that at the end of the experiment, the A-body person gets the money and the B-body person gets the torture. The A-body person will say “that’s what I asked for” and the B-body person will say “this is very much not what I asked for.” That is, the A-body person is saying what we would have expected B to say and the B-body person is saying what we would have expected A to say. That suggests that they switched bodies (164).
If you change the initial choices around, or ask different questions entirely, you get similar results. At the end of the experiment, A seems to be in the B-body and B seems to be in the A-body. So, for example, the B-body person might express surprise about some of the features of his or her body; this is what you would expect if it were new rather than familiar. Or the A-body person might express regrets that he or she still has some of the undesirable psychological traits that B had complained of before the experiment began (165-67).
The experiment, round two.
Suppose someone tells you that you will be tortured tomorrow. You will be frightened: you think that you will be the one feeling the torture. Now suppose someone tells you you will be tortured tomorrow and that your mind will be changed in certain ways: you will lose some of your memories. That still seems scary. Now suppose that you will lose more than your memories; your character will be changed and you will have the character and memories of a fictional person. Still scary, right?
Now take the last step. Your memories and character will be erased and replaced by those derived from a real person. Do you still think that you will feel the torture? Williams thinks the answer is yes. None of the psychological changes described would result in your death. That is why you would anticipate, and fear, the torture. You stay with the body, in other words.
What is interesting is that round two of the experiment is exactly the same as round one, with you in B’s position. We just left A out of the story. Why should you switch bodies in the first round but stay in your body to feel the torture in the second round? Pay special attention to page 172. (167-74)
Objection: the argument turns on our inability to draw a line between (i)-(vi) on page 172. But there are lots of cases like that: this color is orange and that color is red; on the spectrum between the two colors, there will be shades that are neither red nor orange. But the two ends of the spectrum are still orange and red. Williams’s answer to this kind of objection is the most interesting part of the essay, in my opinion. He says that the continued existence of a person is all or nothing. There is no in-between state where it is indeterminate whether I would exist. For any change, I will either be alive or dead. He makes his point by asking us to consider the emotion of fear when thinking about the experiment. (174-80)