The Brain Account of Personal Identity

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This is the 58th post in my Theories of Knowledge and Reality series. The last post looked at bodily accounts of personal identity. As a quick refresher, here is that post's summary of the personal identity views up to this point:

According to the dualist account of personal identity, being the same person is having the same immaterial mind or soul. According to the psychological account of personal identity, being the same person is having a continuation of the same set of psychological properties such as memories, desires, beliefs, personality traits, moral character, and so on. The main contender to those two approaches would be biological accounts, which base personal identity in some biological facts. The most common versions of biological accounts are the bodily account and the brain account. The bodily account takes someone to be the same person just in case they have same continuing body.
The brain view, like the bodily view, looks to biological continuity but not of the entire body, just the brain. One major advantage of this view is that it fits better with the intuition a lot of people have that a brain transplant is not really a brain transplant but a body transplant. If my brain got put into your body, a lot of people would take the resulting person to be me in your body, not you with my brain. A psychological view would give the same result, but psychological views face duplication problems too easily. You can have two candidates for who it is to be me if you continue my memory and personality in two different places, and in certain cases it's too hard to find a decent answer as to why one or the other is a better candidate for being me (such as a Star Trek transporter accident using new matter to reconstruct me, but it creates two of me, and each duplicate is intrinsically just like the other).

It seems at first glance as if the duplication problem doesn't occur quite so easily with the biological views. After all, only one body could plausibly be mine, and only one brain could plausibly be mine. If you put my brain in a new body, the bodily view would say the resulting person is not me, because it's not my original body. If you put my memories and personality in a new brain, the brain view would say it's not me, because it's not my continuing brain.

But John Perry presents a case that makes brain views seem odd too. Suppose I'm dying of brain cancer, and medical technology progresses to the point where you could produce an exact duplicate of my brain except for the brain cancer and then transplant it into my head. They call it brain rejuvenation. I get a new brain, but I seem to continue. A bodily view would be fine with that description of the case, as would a psychological view. But the brain view would say that I die, and someone new but just like me continues on in my body. Many people find such a conclusion at odds with how we would intuitively think about such a case.

A further difficulty for the brain view is that the first-glance sense of no duplication problems turns out to be wrong. You can present duplication problems for the brain. If brain cancer required removing one of my brain hemispheres, but the other one remained healthy, it would seem that I continue to exist in the same body with one-half of my brain. This would be true whether it's the left hemisphere or the right. But what would happen if you transplanted half my brain into a new body while leaving the other in my body? Many would be inclined to say I'm still with the original body, but that would mean the brain view is false, since my continuing body plays a role in determining where I am. But remove that possibility altogether. Just remove both hemispheres and put them both in new bodies. If either brain hemisphere would be me in the absence of the other, and neither body has more right to counting as me than the other, then the duplication problem arises again. Perhaps you could favor the dominant hemisphere, but person with the other hemisphere would certainly wonder why he is less a candidate for being me. He'd wonder why the other guy got to remain married to my wife and remain the father of my children. He'd wonder why all my worldly goods would belong to the other guy. It does seem arbitrary to deny the second hemisphere the rights to something you clearly give to the other, just on the ground that it was the dominant hemisphere when both hemispheres were fully half of me. Each hemisphere would take itself to be me, and it does seem that on the brain view they both have the right to such a claim.

So those are the main views on personal identity. A number of philosophers have been frustrated enough with the difficulties of these views that they have turned to more unconventional approaches to solve the problem. The next post will look at the temporal parts or (four-dimensionalist) solution.


Thanks for writing about these, Jeremy. I have been studying this a lot and haven't come across such nice short summaries as yours.

It seems to me that recently there has been a new view. A "data" based view which views your self as being a collection of data stored in your brain. (this may be the psychological view you mention but it sounds different at least in presentation) This is the view I've heard most in my neuroscience related classes. It seems to be a very popular view with the logical positivist empiricism crowd.

I do think of that as a version of the psychological view. There are people who hold the psychological view who are substance dualists, e.g. Richard Swimburne. He obviously wouldn't go for that. But a lot of psychological theorists think an advantage of their view is that it allows for survival by having your consciousness converted into a computer version that then experiences a virtual reality online.

Are you planning on covering Lynne Rudder Baker's constitution view? I find it very appealing, and would like to see what you think of it.

Her view of personal identity is a psychological account, which I've already discussed. She has an additional view that there's this other thing, a human animal, that is somehow present in the same place and time as the person, and the animal constitutes the person but they are distinct objects, but that's not really a view on what constitutes personhood across time, so it doesn't usually come up when that's the focus. That's really a material constitution issue, which is orthogonal to personal identity questions. I'm interested here in what makes someone the same person across time, and her view on that question is a straightforward psychological one.

I don't think I have anything to say on her view on the material constitution question, beyond what Ted Sider and Dean Zimmerman have said in their reviews of her book. I was present at several discussions that led to their reviews (we read her book for a class I took with Dean), and I think the main objections I've had to her view are captured in those two reviews. Dean's review is much longer and better-explained, but Ted's is much quicker to look through.

Wow, that's a hefty read.

Thanks for the pointers. I admit I only skimmed your discussion of the psychological view, so I must have missed enough indications that hers was similar. Still thanks for the links, I shall try to read all that!

Hey by the way, I was wondering what your thoughts on a how one would approach consciousness from a Christian Mortalist perspective? The Christian Mortalist perspective seems very consistent with the concepts of the soul in the Jewish theology of the OT, and it was considered pretty mainstream up until a couple of hundred years ago.

The reason I ask, is because it seems to me that a Christian Mortalist view would necessitate a theory of identity like the Brain or Psychological account. Thoughts?

Christian mortalism can come in two varieties. The unifying them is that we're no naturally immortal, and thus any immortality is a gift from God. So it's metaphysically possible for our complete annihilation, and it's metaphysically possible for our continued existence after death. But this could be because we have a soul that could be annihilated after death or continued at death, depending on God's choice in our case (in which case we might be working with the dualist view of personal identity) or it could be because of some approach compatible with materialism. So the real question is what a materialist can say about resurrection.

The most famous (infamous?) attempt in philosophy today is by Peter van Inwagen. He says he doesn't have any sense of what the correct answer is, but he's willing to tell a just-so story that he's not sure is the right answer (and probably isn't) in order to explain how it might be possible to allow for resurrection of a material body. It's all well and good to speak of resurrection in cases like Lazarus in John 11 or the widow's son in II Kings raised by Elisha. Their bodies still existed, and God could have miraculously preserved enough to be able to get them working again upon resurrection. But van Inwagen has serious problems with the idea of a cremated body being resurrected, because he holds to a bodily view of personal identity. The newly-created body wouldn't be the same person, on his view. A psychological theorist would have no problem with resurrection of a cremated body, by such a view has duplication problems. What if God made two of them? Neither would be the original.

So van Inwagen proposes that could could miraculously pull the original body out of the earthly realm and into a heavenly realm of some sort just before death (or after it soon enough to preserve its existence) and replaces it with a duplicate that is just a corpse and was never a person, and it's the duplicate that decomposes. Then at resurrection, God just reanimates the preserved body. So he says resurrection is possible, and this shows that it could be, but he's not sure it's right (in fact he thinks it's unlikely) and isn't sure what to say beyond that.

Dean Zimmerman (not a materialist himself) proposes that materialists should say that the closest-continuer is the same person, which amounts to something closer to what a psychological theorists says but about bodies instead of mental characteristics. But that strikes me as having duplication problems too, so I don't think it's a very attractive view. I tend to think materialists don't have a very good answer to this problem, and it's one reason I think Christians ought to be dualists. But the first paragraph in this comment shows how a dualist can be a Christian Mortalist, so someone more convinced of Christian Mortalism than of whether dualism or materialism is true can go that route.

Yeah, I was thinking about the cremated body issue a bit (furthermore, what about the old Sagan "you have an atom from a dinosaur in you"). I guess thats why some groups of orthodox Jewish people have such strict views on funeral preparations, right?

I have to say, I find the materialist view interesting. I was thinking about the cremation thing before, and my initial thought was perhaps some kind of perfect duplication atomically of the person. That of course creates the duplication problem as you mention.

But in this case, is it a problem? If God decided to create a second perfect duplicate, then there would be two people with the same identity. But since we're talking about God, and not some futuristic teleporter it raises a couple of questions.

First, is the hypothetical question relevant? If God never decides to do it, then maybe its really just a miracle. Is having two people somehow fundamentally any more weird than other miracles that put it in another class?

Also maybe the 4D view is helpful here. What if the different identities are only relevant in so far as God holds those thoughts in his mind (excuse the anthropomorphism, I'm thinking along the lines of the Edwards view you mentioned I think). At that point, the two people are different not in their material but in the way that God thinks of them, like how a sculpture might sculpt many copies of a single character, then mash it up and start over with another one. Each new version is what it is by the intention with which it was created, while the individual lumps of clay don't matter so much.

Of course, I think this particular use of the 4D model seems a little counter intuitive to the way we perceive our own selves. But perhaps there is some timeworm issue that could help here.

On a 3D view, can there be two of you, though (barring time travel)? It's not that you have two people. It's that you are two people. Are you wholly present in two places at the same time, like you'd be if you time traveled and met your earlier or later self? Are you just bi-located? Do you have two bodies, and they don't necessarily even know about each other, so that you can be thinking that it's cold here and hot here at the same time without knowing that you're also thinking the other thing? I don't think there's a lot here that will be easy to make sense of metaphysically. It seems the two individuals are not identical with each other, since they're doing different things and have different thoughts from each other. Otherwise you have to say the same person is simply doing both things but in different places, without knowing about what the other is doing (and you can't really say "the other" -- what do you say?).

Most metaphysicians think this is metaphysically impossible. And does it matter if it's God? What if the duplicates just appear out of nowhere for no reason (or not intentional reason)? Does God simply declaring that it's you do it? Does it have to have enough intrinsic similarity to you when you died? Does it have to be exact? If it's just enough that's required, how much is enough? That's an inherently vague notion, and is it vague whether something is you?

The 4D view helps with splitting by saying there are two worms, and they overlap in the initial stages, with each one correctly saying that it was once those early stages and neither later stage able to say that it is the other later stage.

With the duplication issue you seem to be bringing up the problem of the duplicates not being 2 people but of one person being two people: This sounds an awful lot like the Trinity. I don't think the addition of God solves it through arbitrary divine command. Rather I think it sounds consistent with the ideas of personhood understood in Jewish tradition.

Additionally, I'm not sure why you say it is not 2 people but rather 1 person in two places, because the 4D view allows for a split, they were 1 person at one time but now they have become 2 separate people as parts have split off from each other. They share a crossroads in their time worm, and they may have originally been the same person but now there are two separate paths, yes?

Well, you could do it in a number of different ways and be logically coherent, but each has some very weird consequences.

One way to do it is to say that there were two people all along, and they just shared a body until the split.

Another way to do it is to say that one person was there to start with, and then the split occurs and the person is now bi-located in two bodies.

A third thing you could say is that the original person dies, and two new people are created.

A fourth possibility is that one of the resulting people is the original, and the other is not.

The problem with the fourth view is that there seems to be no non-arbitrary way to settle which is the original, at least in some of the fission cases people have come up with.

The problem with the third view is that the mere existence of a second person makes the original die, when either of the resulting people would have been the original if there hadn't been two of them.

The problem with the second view is that you have one person wholly present in two places at the same time. Doesn't that undermine what it means to be wholly present?

The problem with the first view is that you have two people in the same body at the same time, and everything intrinsic property of one is true of the other. Nothing can distinguish them except their different futures. But nothing right now makes there be two of them, and yet there must be two of them. (That's wholly unlike the Trinity, which has distinctions between persons.)

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