Personal identity is a philosophical topic made for thought experiments. The problem of persistence of identity is quite simply posed; as the Stanford Encylopedia for Philosophy entry for personal identity puts it:
What determines which past or future being is you? Suppose you point to a child in an old class photograph and say, “That’s me.” What makes you that one, rather than one of the others? What is it about the way she relates then to you as you are now that makes her you? For that matter, what makes it the case that anyone at all who existed back then is you?
The related problem of self-identity–what makes me the person I am, posed classically as the question ‘Who Am I?’–reveals itself as just as fascinating:
[O]ne’s “personal identity”…makes one the person one is. [It] consists roughly of what makes you unique as an individual and different from others. Or it is the way you see or define yourself, or the network of values and convictions that structure your life. This individual identity is a property (or set of properties).
These problems of persistence of identity and self-identity pose questions like, “If X had not happened to me would I still be who I am?” (Which set of experiences are definitive of my identity), or “If I did not possess this property/behavioral characteristic/personality feature would I still be who I am?” (roughly, Which of my properties are “essential” to my identity?) Almost anyone, including schoolboys, can be perplexed by the thought experiments that lead to these questions.
I should know, because I was a schoolboy once, and these questions managed to stump me.
My childhood attempt at raising a hypothetical situation that prompted these questions came about when I was a space-travel nerd, one that avidly read up on histories of manned space exploration, including biographies and autobiographies of astronauts. Those astronauts that had had long careers struck me as having lived particularly rich lives: they had been pilots (even better, at times they had been military pilots who had flown in combat), they had flown in a variety of spacecraft, gone to the moon, and so on. Among them, James Lovell, the commander of the abortive Apollo 13 mission, stood out just a bit. The first man to fly in space four times–Gemini7 and Gemini 12, and then later, Apollo 8 and Apollo 13–Lovell had gone to the moon twice without landing on it. He seemed to have lived the kind of life a schoolboy could only dream about. So that’s precisely what I did, letting myself dream about living the life Jim Lovell had lived, all the while idly tossing around the thought–I wish I could have been Jim Lovell.
The oddness of this remark soon became clear to me. I had said I wanted to be Jim Lovell because, presumably, I found the descriptions of the experiences he had had exciting, and wanted to have the same ones. But how could I, Samir Chopra, have Jim Lovell’s experiences without being Jim Lovell himself? It seemed me to me that my experiences made me into who I am; Lovell’s experiences made him into who he was. But if it wasn’t me having those Lovell-experiences, what would be the point? Jim Lovell had already had his experiences. If I had them, I wouldn’t be Samir Chopra any more. Rather I would be someone else having those experiences. What would be the point of that? It had soon become clear to me that the person who wanted to have those Jim Lovell-experiences could not experience them in any other way than wistfully; I could perhaps watch a movie or read a book about them but I couldn’t have Jim Lovell-experiences without being someone else and changing the point of wanting those experiences for myself. To actually have them would be to be someone else, and that wouldn’t do anything to satisfy the person who had expressed the wish in the first place. At best, it seemed to me, as I thought about it further, I could have said, “I wish I had lived a life that included the kinds of experiences Jim Lovell had.”
I’m not sure how old I was, and I don’t know how clearly I have managed to recapitulate my line of thought at the time. But I’ve remembered its rough details well enough to recount this little anecdote to many classes I’ve taught over the years. I think my students find it a little wacky that I went so far with that line of speculation, but they still find it an engaging point of entry for talking about personal identity.