Identity

Could I have been my sister? Thanks, Bob.

Comments

Tricky question, but I'm inclined to say no. If you were your sister, what would have happened to her? I think she and you would have to be the same person. But I don't think two people could have been one person. (It's not like Clark Kent and Superman. That is one person in a situation where it is wrongly thought (by Lois Lane, anyway) that there are two people.)

But perhaps the question is not whether the two of us could have existed as one, but whether I could have been her. It’s certainly easy to imagine oneself as another person (well, perhaps not so easy), and this sympathetic imagination easily leads to the question whether I could have actually been the person whose experiences I’m imagining? Could I have been Napolean? If my mother had waited just a few minutes before having sex with my father, would I have been a different person (since undoubtedly a different sperm and egg would have united)? If my mother had had sex with a different man, would I have been an even more different person?

Try this question: Could you have been your sister and your sister been you and everything else been pretty much as it is? I find it kind of hard to get my mind around that: In what precisely would it consist that you were her and she were you? There are certain conceptions of the soul that would make sense of that: Your soul would occupy her body and hers would occupy yours. But even those philosophers attracted to a notion of soul have usually thought the soul was more intimately connected to the body than that: If we accept that kind of possibility, who's to say souls aren't switching bodies every time someone falls asleep?

So suppose we agree that isn't possible. Now it clearly is possible that she should have existed without you. But could it have happened that you should have existed without her but, so to speak, as her? What on earth is that supposed to mean? Either she exists or she doesn't, and if she doesn't exist, then you can't be her. (Perhaps you could have looked like her and acted like her and so forth, but that isn't what's at issue.)

But we can try to imagine that possibility a different way: Could you both have existed but been the same person? (This is Peter Lipton's question.) That one's not so clear to me. A case that might seem plausible would be that of identical twins. So here are Don and Dan, separate persons only because the blastocyst from which they were formed split early in its development. Suppose it hadn't split. What, then, should we say about Dan and Don? Would they have existed? It seems difficult to suppose that only one of them would have existed: Which one? But maybe it also seems difficult to suppose that neither of them would have existed, and, if so, then perhaps one should conclude that both of them would have existed but been the same person. But of course that's a special case, and one that probably doesn't apply to you and your sister.

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Could I have been my sister?Thanks, Bob.

Could I have been my sister?Thanks, Bob.

Could I have been my sister? Thanks, Bob.