Suppose you are 40-something years old. You remember growing up, getting married, having children, etc. Basically, a standard life with standard memories. Then it’s shown to you, incontrovertibly, that all of your memories from before you were 25 are false; they were implanted. The body you inhabit had been inhabited by a serial killer. Doctors took the serial killer, placed her in a coma state, and fed dreams into her head electronically. Over the course of a year these dreams replaced her prior memories. No surgery was involved, just the process by which all our memories are altered over time: we remember something, a detail is added, another subtracted, and slowly our memories are altered. (This is well-established in psychological studies of memory, by the way, and it’s possible to create false memories using this method–not the coma, just making suggestions to people as they are asked to remember things–, though I doubt anyone’s ever tried it on this scale.)
When you learn that about the serial killer, do you think that she was (A) you, (B) sort of you and sort of not you or (C) not you at all? Or maybe a better question is: do you feel yourself to be identical to the serial killer? Do you share her identity?
I think what’s interesting here is that many of us (maybe most) don’t have a clear sense of how to answer this (or we take the B answer). Ultimately, I think a lot of these cases point to problems with our overly rigid notion of continuity of identity: we want there to be answers in all cases (that’s why we get “it’s body,” “it’s psychological continuity,” etc, put forward as the criteria), but I think the fact that there aren’t clear-cut answers (and even if one person has a strong sense of what’s the right answer in all cases, repeated studies have shown a tremendous amount of disagreement in many such cases, so there’s no consensus here, and no clear standards to appeal to–I’ll return to this claim) is helpful in showing us the complexity of the concept of self/person/identity/continuity.
From a forensic perspective, here are some interesting real-world cases that show, even for legal purposes, bodily continuity is not sufficient for identity: the courts have ruled that a person with split personalities was not responsible for what her other personality did:
(There have been a few other cases like this too, and cases where a person was found guilty because it was thought that he/she was faking the split personality.) I should note I’m a bit of a skeptic on the actual existence of split-personality, at least of the sort where one personality has no access to the memories of the other. Nonetheless, it’s interesting that in such a case, a court would rule (rightly, I think, if the claims of split-personality were true) that one personality is not responsible for the doings of the other.
This is because, in general, bodily identity is not enough for guilt; the law demands that there be a degree of psychological connection to the criminal action, which is why mens rea is a necessary element of a crime. In R. v Parks, in Canada, the supreme court upheld the acquittal of a man who committed murder while sleepwalking; in fact, the point of contention was not whether a sleepwalker was responsible for murder; it was agreed that a sleepwalker was not; it was whether he was lying about sleepwalking. So again, bodily identity is not sufficient for forensic purposes.
But it seems obvious that in a will or property case, bodily identity may well be sufficient. If someone leaves person X some money, I doubt total memory loss for person X would negate the will (barring some specific language in the will to that effect.) So in _some_ legal contexts, the body is what’s relevant. In some, it’s not condition.
Again, this goes back to the claim that the question of continuity of identity is several questions that have to answered in specific contexts.
I’ll also note, briefly, that the method of pumping intuitions and looking at cases is helpful here not because it points us to the “true person” or “real self” or whatever the target of a personal identity inquiry is, but because the multiplicity of answers shows that we don’t have a single, consistent answer to that question. Further, it’s not just popular confusion that could be cleared up by an expert inquiry into the real self, or real person, or what have you. Instead, I think what we’re seeing is that a number of different senses of continuity of identity are at play in our social practices. It’s not that these practices can’t be mistaken, but that there’s no fundamental reason, no raw data, that’s entirely separate from social practices, that we can point to in all cases as the final word on how we should act. Sometimes a physical criteria is best. Sometimes a psychological criteria. And sometimes one physical criteria makes more sense than another (“the functioning brain” might be our physical criteria, but if the brain ceases to function the bodily entity probably still has plenty of ownership rights, for example, but no longer has (I’m guessing) voting rights or parental rights.) Marya Schechtman’s discussion of the mother in the late stages of dementia does a nice job of noting when we accept a pure bodily criteria, and how much is lost in making this the sole criteria (see “Personhood and the Practical” in Theoretical Medical Bioethics, 31:271–283, 2010)
Exploring these multiplicities, again, tells us something about what people hold as important in identity.