What makes us who we are? Our bodies? Our minds? Our moral character? “The most natural theory of personal identity,” writes the philosopher Richard Swinburne, is that it is “constituted by bodily identity” (Personal Identity, Oxford, 1984). There are obvious problems with this theory, though. The brain, seems more important than the rest of the body. A person can lose an arm or a leg and still be obviously the same person. Damage to the brain is different. A person who suffers severe memory loss, or a dramatic personality change, as a result of a brain injury or degenerative brain disease is not so obviously the same person they were before. 

“The traditional alternative to a bodily theory of personal identity,” continues Swinburne, “is the memory-character theory.” According to this theory, it’s the continuity of our memories and our character that constitutes our selves. But which is more important, memory or character?

Our sense of self is closely connected with our memories, or more specifically, with the personal narratives we construct based on those memories. If the memories go, then so do the narratives. If we reach a point where we can no longer remember who we were, then the person we were is gone. There’s still a person there, of course, but it is, in an important sense, a different person, a new person, a person with no past. 

Recent work in “personal identity theory” has shifted its focus from memory to character, or more specifically, to moral character. Research done by Nina Strohminger, a psychologist at the Wharton School of the University of Pennsylvania, and Shaun Nichols, a philosopher at the Sage School of Philosophy at Cornell showed that the extent to which someone suffering from Alzheimers seemed different to those close to them was determined almost entirely by changes in their moral character rather than by memory loss (“Neurodegeneration and Identity,” Psychological Science, Vol. 26 [9] 2015 pp. 1469-1479). 

The primary aim of Strohminger’s and Nichols’ study, they explain, “was to determine the influence of neurodegenerative symptomatology on third-person judgments of personal identity” (p. 1470). But a theory of personal identity that locates that identity outside a person’s own sense of self is deeply unsatisfying.

Here’s the puzzle. It makes sense to suppose that character is constitutive of who we are. On closer examination, however, it seems neither necessary nor sufficient for personal identity. Or more correctly, whether it’s either necessary or sufficient would appear to depend on one’s perspective. So long as people retain a critical mass of the memories that make up their personal narratives, their characters can change and even change dramatically, without threatening their sense of self. That is, character can change without any corresponding change of personal identity from the first-person perspective. If people’s characters change enough, however, they will seem like different people to others, which is to say they will seem like different people, from the third-person perspective.

Conversely, people can experience such profound memory loss that they no longer have a coherent personal narrative and hence completely lose their sense of self. Memory loss does not necessarily affect character, however. So these same people who are no longer the person they were from the first-person perspective, may remain recognizable as the same person to others, which is to say, from the third-person perspective.

So it appears the judgment of whether a given person is “the same person” after significant memory loss as they were before depends on the perspective from which one makes the judgment. Someone whose personality remains recognizably the same will appear to be the same person from the third-person perspective, which is to say from the perspective of people who knew them before, even if they have entirely lost their own sense of who they used to be. On the other  hand, a person can retain their subjective sense of self even after personality changes that make them effectively unrecognizable to others.

So it seems that just like electrons will appear to be either waves or particles depending on how one observes them, so can we appear to be either the same person we have always felt ourselves to be, or an entirely different person depending on who’s doing the observation, ourselves or someone else.

But which perspective are we to take as definitive? The first person or the third person? Philosophers, as Thomas Nagel observed so compellingly in The View From Nowhere (Oxford, 1989), are biased in favor of objectivity, which is to say, they are biased in favor of the third-person perspective.

Do other people really have the final say, though, on who we are?