Switching bodies Notes for November 16

Main points

Locke’s case for his view of personal identity depends heavily on examples. Thus he invites you to imagine someone who had Socrates’s soul but could not remember any of Socrates’s thoughts or experiences. Thinking about a case like this is supposed to lead you to the conclusion that having the same soul as Socrates is not a sufficient condition of being the same person as Socrates. Or suppose the person who woke up in the Cobbler’s body could remember the Prince’s thoughts and experiences. This is supposed to convince you that one person can be more than one man, where a man is a living human body.

Williams challenges the second kind of case. Specifically, he describes it twice. One description is the one that is familiar enough from the movies: two people seem to switch bodies. The other description is exactly the same, only it leaves out the second person. When described in this way, we are strongly inclined to say that the person stays with the body. All that happens is that the person starts believing that he or she is someone else.

So what do Locke’s cases tell us? Williams is suspicious.

Williams’s spectrum

One person can change in many ways while still remaining the same person. I don’t die when I get a haircut, despite the fact that this makes me physically different. By the same token, I can survive lots of psychological changes. I can learn new things, forget old ones, change character, and so on. I may become qualitatively different over time while remaining numerically the same person.

The core of Williams’s argument is a spectrum of cases. At one end are changes that most of us think a person can undergo while remaining the same. I can suffer amnesia while remaining the same person, for instance. At the other end is the apparent body switch: my body gets an entirely new set of memories and character traits derived from someone else’s mind while their body gets memories and character traits derived from my mind. This is the sort of thing that I had described as a possible medical treatment in the future: beat cancer by switching bodies! But Williams tries to show that if I think I can survive amnesia in my old body, I would stay in my old body even after my memories and character traits are copied into a different body.

The challenge for those who disagree with him is to draw a line between one kind of case and the others, such that on one side of the line, you stay with your body while on the other you leave your body, either by dying or by switching to a different body.

Harley started off our discussion by trying to draw the line at the first step: amnesia. I think it’s fair to say that most opinion was against him. But it was surprisingly difficult to show he is mistaken with an argument.

Here’s a suggestion. We normally think that memory loss does not disrupt personal identity. I can forget everything that I thought and experienced on March 28, 2006. But, most of us think, I now am still identical with someone who was alive on that day: Michael Green!

Amnesia, you might argue, is just a more severe case of memory loss.

Williams provided a different way of arguing against Harley. It’s possible to suffer amnesia and still feel something, such as torture. If you think it makes sense to fear feeling the torture even after suffering from amnesia, then you think that you’ll still be around, in your original body, even after suffering from amnesia.

I think Harley could consistently refuse to accept these arguments. He might dig in his heels with Locke and insist that I can’t be the same person as someone from the past whose thoughts and experiences I cannot remember. And he might challenge us to prove that it is possible to suffer amnesia and then feel what happens to what was your body before suffering amnesia. I don’t know how to do that myself, except to say that I don’t see how memory could be necessary for feeling pain.

We’ll talk more about different points on the spectrum next time. We’ll also spend a lot of time talking about Noah’s question about why we have to make a choice. I think that leads us to something quite interesting about people. We think that our existence is an all or nothing matter rather than a matter of degrees. In this way, we are different from nearly everything else.

This page was written by Michael Green for Problems of Philosophy, Philosophy 1, Fall 2009. It was posted November 16, 2009.
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