On Cohen and Miller’s analysis, Julia has had two bodies — her original one and Mary Frances Beaudine’s. Cohen and Miller agree that "Julia’s brain in Mary Frances’ body" must be Julia. In fact, most people, and the (fictional) U.S. Supreme Court, agree. The argument is that the brain is the seat of one’s psychological characteristics and memories — the elements that make one oneself. What matters is that Julia’s psychological states be been preserved; if Julia's psychological states have been preserved, Julia has been preserved. This person probably believes herself to be Julia, has Julia’s psychological characteristics, and thinks she has Julia’s real memories; furthermore, this person has Julia’s memories in the right causal way, because she’s got Julia’s brain. That Mary Frances’ body has been preserved simply does not matter, because bodily identity does not determine personal identity.

Weirob acknowledges that most people would think this is Julia. But Weirob disagrees. Weirob denies that Julia has had two bodies; Weirob thinks Mary Frances has had two brains. What matters for Weirob is that Mary Frances’ body is preserved. For Weirob, remember, a person is a live human body, and since Mary Frances’ body is still alive, this person is Mary Frances — not Julia, whose body is dead, and who is therefore dead, on Weirob’s view. A brain is a body part, after all. A person is not a body part. If my arm were cut off, no one would say I’ve ceased to exist — that my body without the arm is no longer me. I’m still the same person without my arm. In the same way, if my brain is removed, we shouldn’t say the body without the brain is no longer me. I’m still the same person without my brain.

The "WHO?" person only appears to have Julia’s memories, etc. She thinks she has Julia’s memories, but she is wrong because she simply doesn’t know who she really is. According to Weirob, she’s really Mary Frances with a new brain. Weirob is relying on our ordinary intuition that a person with a transplanted heart or kidney, for example, is still the same person. It would be absurd to suggest that a person who receives a transplanted organ becomes the dead person whose heart or kidney was donated.

The question is real, too, not just a matter of how we talk — aspirin example (41).

To Cohen and Miller’s astonishment, Weirob reveals that she has been offered the very same operation (a transplant of her brain into a different body), but has refused because she does not think the resulting person would be her!

What’s Weirob’s reasoning behind this surprising decision? It’s a version of the duplication argument from the Second Night. It's an extended thought-experiment.

Suppose, she says, that it were possible to duplicate her brain, preserving all information — like "Hubert" in Dennett’s story. Hubert, as you recall, existed only virtually; he had no body, and could not be copied into a living human body. But suppose it were possible to create a duplicate of Gretchen's brain, preserving all information (like Hubert's) AND capable of being implanted in a living body (unlike Hubert's). Got the picture? Weirob calls this a "brain rejuvenation."

Well, as a matter of fact, Weirob says, if she could have this kind of surgery, she would agree to it. She’d happily take a copy of her own brain, if it could be implanted in her own body. But alas, that surgery would require Weirob’s body to be healthy, just the opposite of her current physical situation. But if it were possible, Weirob would agree to it, because she thinks she’d still be herself afterwards.

So here's what Weirob would accept:

BEFORE		AFTER
Weirob's brain ("rejuvenated")		Copy of Weirob's brain
in	→	in
Weirob's body		Weirob's body

The thought experiment continues. If this brain rejuvenation were possible, i.e., if it were possible to create a copy of Gretchen's brain capable of being implanted in a living body, then it would presumably be possible to create multiple copies of Gretchen's brain. If the technology existed to create one, then surely the same technology could be used to create others. Suppose one other copy were created, say, and implanted into another living body, as shown below; it doesn't matter whose body. In Dennett's words, "some Johnny-come-lately Rosencrantz or Guildenstern" would do. One copy of her brain goes into her body, resulting in Person #1. The other copy goes into a different body resulting in Person #2.