Admiral Nelson sails out with his flagship the HMS Victory. The ship takes quite a beating in battle. Upon her return, various parts have to be replaced: the masts, several cannons, some other bits and pieces, before Nelson can take her out to war again. Battle after battle, the HMS Victory sustains damage, gets the necessary parts replaced, and sails out again, until Admiral Nelson realises that each and every part of the original HMS Victory has been replaced. He scratches his head and asks himself: Is this ship really the same HMS Victory, or is it a different ship?
Now suppose that the HMS Victory had changed a lot as a result of all the work that has been done on her: higher masts, technical improvements, different layout, a more streamlined shape, different colours… would it still be the same ship? If so, in what sense?
The HMS Victory is not a person, she is a ship. Still, we can ask a similar question about human persons. The problem is, that when we talk about human persons, the question might get a bit more complicated.
I was born in 1983. I don’t remember anything of this period, but there are pictures to prove it, my mother says that chubby baby is me, and so says my birth certificate. I do remember going to school. I was studious, drawing and reading all the time. I also remember being a teenager, listening to teenage-anxiety-rock, like Nirvana and Alanis Morisette. I also remember being a student, trying to pass my logic and metaphysics exams, thinking that everybody was cleverer than I was. I also remember events and encounters that made me a different person in some way or other: boyfriends, breakups, deaths of loved ones, meetings with inspiring people, poems, films, books. Physically, I think nearly every cell I used to have when I was a child has by now been replaced, some of them thousands of times over. There is no doubt that I am qualitatively a different person than I used to be at various times in my personal history, but I somehow still think it’s all me. No matter how much I’ve changed, it’s me who did the changing. I am still one and the same, I’m still numerically the same person.
A lot has been said about personal identity in the qualitative sense. When can we truly make statements like “she was a different person after the divorce” or “after fighting in the war, they will never be the same again” or “He wasn’t himself at all when he was under the influence of LSD”? A question like this asks which qualities or characteristics are fundamental to our being, and which are more peripheral. It’s an ethical question, it has to do with values, or with what it means for a person to live a fulfilled or authentic life*. But in this class, we’ll discuss personal identity in the numerical sense. That, in contrast, is a metaphysical question: when do I start and stop existing? How can we tell it is one and the same person undergoing a change, or two different persons at two different times altogether? In this metaphysical sense, one cannot fail to be oneself, since everything is logically self-identical. Heraclitus confused the qualitative with the numerical question when he said “you can’t step into the same river twice”. The river changes continuously, so is never qualitatively the same as a moment ago, but it’s still numerically the same river that is changing.
So what determines my numerical identity? What makes it so that I’m still the same person as the baby in 1983?
Is it my physical continuity? This is problematic. Suppose one day I would wake up in your body, and you wake up in mine. We would still say that it is me who wakes up in your body, and not you. If you’re not convinced: suppose you wake up in my body one morning, and I in yours. However, when you (in my body) set out to look for your own body, hoping to get it back, you discover that it has been destroyed in a horrible accident – and I along with it. You now have my body and no hope of ever getting your own back. No doubt, this will mean a great qualitative change for you, but numerically, you still exist – albeit in my body – and I don’t. So physical continuity cannot determine personal identity.
How about psychological continuity? Locke thought one is the same person if one remembers being an earlier version. But this is problematic. I don’t remember large parts of my life. Most of my time asleep, for instance. It would be weird to say that I stop existing whenever I fall asleep, and that the human-shaped living and breathing and dreaming thing in the bed is not a person, let alone me. I’ve also forgotten many trivial things, like a great number of supermarket visits or dog walks. Does that mean it wasn’t me who walked the dog or bought the groceries? No, I’ve simply forgotten it. So memory can’t constitute personal identity either. But how about a more sophisticated psychological continuity view? What if we take into account not only memory, but other mental states, including unconscious or forgotten ones? Then the baby, the schoolgirl, the student and I are the same person because my current mental state, whatever that may be, is the last of an unbroken chain of mental states which began a short time before my birth. But this raises another question: how do we determine the connection between these mental states? One moment I’m awake and aware, the next moment I’m asleep and unconscious. Who is to tell what connects the waking mental state with the sleeping mental state, and thus the waking me with the sleeping me? If physical continuity nor memory can offer an answer, then this is a problem of the psychological continuity view.
One possible solution is the narrative view. This view is explained, criticised, and revised in this video by Elisabeth Camp. According to the narrative view, I am the same person as the baby, the schoolgirl and the student, if these episodes are episodes in the story I tell about myself in order to make sense of myself as a person. This view has advantages. It helps explain why the numerical personal identity question is more interesting when applied to human persons than, say, to the HMS Victory. But even in the case of the HMS Victory, it explains why Nelson can still call the ship the HMS Victory and consider it the same ship, in spite of the replacement of all her parts, her qualitative changes and her lack of a mind. Since the HMS Victory was gradually fixed and amended, it forms a narrative about the ship that makes sense. If she had been destroyed completely and replaced in one go with just another ship, then that new ship would not be seen as the same ship, but a different one. However, a disadvantage of the narrative view is that it brings the qualitative personal identity question back on board. It makes it an ethical rather than metaphysical question, one about what it means to make sense of a life, rather than what it means to be someone – someONE-and-the-same – who is doing the sense-making. In addition, it seems too narrow. Who is to decide on how the narrative of myself goes? Me? Sounds lovely, but not every human person is capable of narrating anything at all. Most people have a hard time constructing a coherent narrative of themselves, but some are unable to at all: comatose patients or someone who dies aged 3 or so. Would such people not count as persons, or would we be unable to tell whether they are one and the same person?
Where does this leave us? Should we follow Hume in saying that we’re looking for something that can’t be found, because there is no such thing as a person that persists through time? So far, not a single characteristic has been formulated that can solve the puzzle. Combination theories, involving some physical and some psychological criteria, might be promising. But the exact formula is yet to be found.
An excerpt from Philosophy for AS, an A-level textbook written by my colleague Michael Lacewing, is available online here. It gives a clear overview of the various physical and psychological continuity views and some additional problems and objections (i.e. the duplication problem).
* You may think: “but this qualitative sense, that’s what I’m much more interested in!” I understand. Don’t worry. We’ll discuss this qualitative question of personal identity in another class, I promise.