I would like to add onto this that universalism about personal identity is also the only way to avoid Cartesian dualism in the following scenario:
I'm comfortable with the idea of some kind of dualism, although not with Descartes'.
Recall that without the connecting fibers between the left and right hemispheres of a single brain, each hemisphere's experience will fall prey to the illusion of being the entirety of that person's experience.
In this case, there are effectively two disconnected, and therefore different, minds to be experienced. Yes, one person, but that's not essential to how the split brain is experienced.
There's no illusion. Each brain will have its own distinct mind, and each mind will have its own idea of what person it is, and I think we can assume those two ideas would be substantially different, for example in terms of perception or in terms of memory etc.
Restoring the connection, if that were possible, would make it immediately clear that both experiences were happening to the same person. Someday, it might be possible to integrate many brains together in the same way that the hemispheres of a single brain are integrated. What would that experience would be like, and who would be having that experience?
Yeah, I already discussed this.
Initially, I suspect that each of the two reconnected halves of the brain will still have its own distinct self. All you'll have will be a very confused individual requiring time to reconstruct his one self.
I think the second question is much easier than the first! If my brain were connected to 10 others in such a way, how could I fail to experience whatever would happen next? And, since all of the sensory information would be shared among all the brains, there would be nothing "missing" from my experience that would differentiate me from the owners of the other 10 brains, so I would have to conclude that I was simply the same person as all of them. I don't think there's any way to maintain that I became the same person as them due to the connection (what happened to the individual persons that existed beforehand?), so I must have been the same person all along.
I think that where you go wrong is when you try to maintain the fiction of personhood as one entity existing at different, successive moments in time. That's your illusion, because there is in fact no such entity. The only sense of being a person is through our sense of self, which is itself essentially whatever memorised biographical data you remember. So, in effect, we are something else at every moment in time because our biographical data cannot possibly stay the same. But there is usually broad continuity in our biography, enough of it at least, to support our notion of being the same person, but that doesn't make us the same thing as what we were a moment ago. Again, personhood has essentially a social utility so it's no surprise that we should want to stick to it as something essential. But it's only essential to our social life. It's not fundamental. I will be whatever person comes out of the biographical data I can remember.
Again, I think there's not much difference between us. Essentially, I locate all the me-ness in the self, i.e. essentially the remembered biographical data. I see experience as entirely impersonal, entirely lacking personhood, entirely lacking me-ness. It's a blank screen on which the brain project our self.
But later on, if the connection were deactivated, which of them would "I" return to? It's tempting to think I would just experience being a lone brain again (and maybe the same one I thought was my "only" brain before the linking with the other 10), but that would imply something like a soul, a ghost-in-the-machine that hops into a swimming pool with some other souls and then hops out, making sure not to hop into the "wrong" one. That can't be the case. It must be true, then, that I would still be "in" all of the brains, and since this couldn't be the result of linking them together (or else we're back into some kind of weird mental essence being spread around), it must have always been this way. In summary, the only way to avoid naive Cartesian dualism about the mind is to recognize that I am the same person as anyone who has an experience I would regard as first-person if our brains were appropriately integrated.
Once the connection is removed, we're back to what we were previously, essentially each one feeling being a distinct person. And that would be an accurate perception. The difficulty would be in reconciling the person now and the person while these people were all connected. There's a serious discontinuity there, one I suspect would cause serious psychological difficulties for all those concerned.
So, I guess I assume a form of dualism, i.e. experience and minds. Experience would work relative to minds (or relative to brains) as space works relative to objects. So no big metaphysical problem there I think.
EB
