Punishment and amnesia

There is an interesting philosophical literature on whether it is appropriate to punish someone who has amnesia with respect to the wrong they have done.

It has just occurred to me (and it would be surprising if it’s not somewhere in that literature) that it is obvious that rewarding someone who has amnesia with respect to the good they have done is appropriate. To make the intuition clear, imagine the extreme case where the amnesia is due to the heroic action that otherwise would cry out for reward.

If amnesia does not automatically wipe out positive desert, it also does not automatically wipe out negative desert.

"Swapping memories"

In Shoemaker’s Lockean memory theory of personal identity, in the absence of fission and fusion personal identity is secured by a chain of first-personal episodic quasimemories. All memories are quasimemories, but in defining a quasimemory the condition that the remembered episode happened to the same person is dropped to avoid circularity. It is important that quasimemories must be transmitted causally by the same kind of mechanism by which memories are transmitted. If I acquire vivid apparent memories of events in Napoleon’s life by reading his diaries, these apparent memories are neither memories nor quasimemories, because diaries are not the right kind of mechanism for memory transmission, and so Shoemaker can avoid the absurd conclusion that we can resurrect Napoleon by means of his diaries. If you wrote down an event in a diary, and then forgot the event, and then learned of the event from the diary, you should not automatically say “I now remember” (of course, the diary might have jogged your memory—but that’s a different phenomenon from your learning of the event from the diary).

It seems to me that discussion of memory theory after Shoemaker have often lost sight of this point, by engaging in science-fictional examples where memories are swapped between brains without much discussion of whether moving a memory from one brain to another is the right kind of mechanism for memory transmission. Indeed, it is not clear to me that there is a principled difference between reading Napoleon’s memory off from a vivid description in his diary and scanning it from his brain. With our current brain scanning technology, the diary method is more accurate. With future brain scanning technology, the diary method may be less accurate. But the differences here seem to be ones of degree rather than principle.

If I am right, then either the memory theorist should allow the possibility of resurrecting someone by inducing apparent memories in a blank brain that match vivid descriptions in their diary (assuming for the sake of argument that there is no afterlife otherwise) or should deny that brain-scan style “memory swapping” is really a quasimemory swap and leads to a body-swap between the persons. (A memory swap that physically moves chunks of brain matter is a different matter—the memories continue to be maintained and transmitted using the usual neural processes.)

Memory theories of personal identity and faster-than-light dependence

Consider this sequence of events:

• Tuesday: Alice’s memory is scanned and saved to a hard drive.
• Wednesday: Alice’s head is completely crushed in a car crash.
• Thursday: Alice’s scanned memories are put into a fresh brain.

It seems that on a memory theory of personal identity, we would say that fresh brain on Thursday is Alice.

But now suppose that on Thursday, Alice’s scanned memories are put into two fresh brains.

If one of the operations is in the absolute past—the backwards light-cone—of the other, it is easy to say that what happens is that Alice goes to the brain that gets the memories first.

Fine. But what if which brain got the memories first depends on the reference frame, i.e., the two operations are space-like separated? It’s plausible that this is a case of symmetric fission, and in symmetric fission Alice doesn’t survive.

But now here is an odd thing. Suppose the two operations are simultaneous in some frame, but one happens on earth and the other on a spaceship by alpha-Centauri. Then whether Alice comes into existence in a lab on earth depends on what happens in a spaceship that’s four light-years away, and it depends on it in a faster-than-light way. That seems problematic.

One-thinker colocationism

Colocationists about human beings think that in my chair are two colocated entities: a human person and a human animal. Both of them are made of the same stuff, both of them exhibit the same physical movements, etc.

The standard argument against colocationism is the two thinkers argument. Higher animals, like chimpanzees and dogs, think. The brain of a human animal is more sophisticated than that of a chimpanzee or a dog, and hence human animals also have what it takes to think. Thus, they think. But human persons obviously think. So there are two thinkers in my chair, which is innately absurd, plus leads to some other difficulties.

If I were a colocationist, I think I would deny that any animals think. Instead, the same kind of duplication that happens in the human case happens for all the higher animals. In my chair there is a human animal and a person, and only the person thinks. In the doghouse, there is a dog and a “derson”. In the savanna, one may have a chimpanzee and a “chimperson”. The derson and the chimperson are not persons (the chimperson comes closer than the derson does), but all three think, while their colocated animals do not. We might even suppose that the person, the derson and chimperson are all members of some further kind, thinker.

Suppose one’s reason for accepting colocationism about humans is intuitions about the psychological components of personal identity: if one’s psychological states were transfered into a different head, one would go with the psychological states, while the animal would stay behind, so one isn’t an animal. Then I think one should say a similar thing about other higher animals. If we think that that an interpersonal relationship should follow the psychological states rather than the body of the person, we should think similarly about a relationship with one’s pet: if one’s pet’s psychological states are transfered into a different body, our concerns should follow. If Rover is having a vivid dream of chasing a ball, and we transfer Rover’s psychological states into the body of another dog, Rover would continue the dream in that other body. I don’t believe this in the human case, and I don’t believe it in the dog case, but if I believed this in the human case, I’d believe it in the dog case.

What are the reasons for the standard colocationist’s holding that the human animal thinks? One may say that because both the animal and the person have the same brain activity, that’s a reason to say that either both or neither thinks. But the brain also has the same brain activity, and so if this is one’s reason for saying that the animal thinks, we now have three thinkers. And, if there are unrestricted fusions, the mereological sum of the person with their clothes also has the same brain activity, thereby generating a fourth thinker. That’s absurd. Thus thought isn’t just a function of hosting brain activity, but hosting brain activity in a certain kind of context. And why can’t this context be partly characterized by modal characteristics, so that although both the animal and the person have the same brain activity, they provide a different modally characterized context for the brain activity, in such a way that only one of the two thinks?

This one-thinker colocationism can be either naturalistic or dualistic. On the dualistic version, we might suppose that the nonphysical mental properties belong to only one member of the pair of associated beings. On the naturalistic version, we might suppose that what it is to have a mental property is to have a physical property in a host with appropriate modal properties—the ones the person, the derson and the chimperson all have.

I think there is one big reason why a colocationist may be suspicious of this view. Ethologists sometimes explain animal behavior in terms of what the animal knows, is planning, and more generally is thinking. These explanations are all incorrect on the view in question. But the one-thinker co-locationist has two potential answers to this. The first is to weaken her view and allow animals to think, but not consciously. It is only the associated non-animal that has conscious states, that has qualia. But the conscious states need not enter into behavioral explanations. The second is to say that the scientists’ explanations while incorrect can be easily corrected by replacing mental properties with their neural correlates.

Appropriateness of memory chains

A lot of discussion of memory theories of personal identity invokes science-fictional thought experiments, such as when memories are swapped between two brains.

One of the classic papers is Shoemaker’s “Persons and their Pasts”. There, Shoemaker accounts for personal identity across time, at least in the absence of branching, in terms of appropriate causal connections between apparent memories, not just any causal connections.

This matters. Imagine that Alice and Bob both get total memory wipes, so on the memory theory they cease to exist. But the person inhabiting the Alice body then reads Bob’s vividly written diary, which induces in her apparent memories of Bob’s life. I think most memory theorists will want to deny that after the reading of the diary, Bob comes back to life in Alice’s body. Not only would this be a highly counterintuitive consequence, but it would violate the plausible principle that whether someone is dead does not depend on future events, absent something like time travel. For suppose this sequence:

• Monday: Memory wipe

• Tuesday: Person inhabiting Alice’s body lives a confused life

• Wednesday: Person inhabiting Alice’s body reads Bob’s diary, comes to think she’s Bob, and gains all sorts of “correct” apparent memories of Bob’s life.

On Wednesday, the person inhabiting Alice’s body has memories of the person inhabiting Alice’s body on Tuesday, so by the memory theory they are the same person. But if on Wednesday, it is Bob who inhabits Alice’s body, then Bob also already existed on Tuesday by transitivity of identity. On the other hand, if Alice hadn’t read the diary on Wednesday, Bob would not have existed either on Wednesday or on Tuesday. So whether Bob is alive on Tuesday depends on future events, despite the absence of anything like time travel, which is absurd.

To get around diary cases, memory theorists really do need to have an appropriateness condition on the causal connections. Shoemaker’s own appropriateness condition appears inadequate: he thinks that what is needed is the kind of connection that makes a later apparent memory and an earlier apparent memory be both of the same experience. But Alice’s induced apparent memories are of the experiences that Bob so vividly described in his diary, which are the same experiences that Bob set down his memories of.

What the memory theorist should insist on are causal chains that are of the right kind for the transmission of memories, modulo any sameness-of-person condition. But now it is far from clear that the science-fictional scenarios in the literature satisfy this condition. Certainly, the scanning of memories in a brain and the imposition of the same patterns on a brain isn’t the normal way for memories to be causally transmitted over time. That it’s not the normal way does not mean that it’s not an appropriate way, but at least it’s far from clear that it is an appropriate way.

It would be interesting what one should say about a memory theory on which the appropriate causal chain condition is sufficiently strict that the only way to transfer memories from one head to another would be by physically moving the brain. (Could one move a chunk of the brain instead? Maybe, but only if it turns out that memories can be localized. And even so it’s not clear whether coming along with a mere chunk of the brain is the appropriate way to transmit memories; the appropriate way may require full cerebral context.) Such a version of the memory theory would not do justice to “memory swapping” intuitions about the memories from one brain being transferred to another. And I take it that such memory swapping intuitions are important to the case for the memory theory.

Here’s another implausible consequence of this kind of memory theory. Suppose aliens are capturing people, and recording their brain data using a method that destroys the memories. However, being somewhat nice, the aliens then use the recording to restore the memories, and then return the person to earth. On the memory theory, anybody coming back to earth is a new individual. That doesn’t seem quite right.

A challenge for the memory theorist, thus, is to have an account of the appropriate causal chain condition that is sufficiently lax to allow for the memory swap intuitions that often motivate the theory but is strict enough to rule out diary cases. This is hard.

Leibniz's King of China thought experiment

Leibniz famously offers this thought experiment:

Supposing that an individual were to instantly become King of China, but on the condition of forgetting what he has been, as if he was completely born again—isn’t that practically, with regard to perceivable effects, as if he were to be annihilated and a King of China were to be created in the same moment in his place? This the individual has no reason to desire. (Gerhardt IV, p. 460)

The context is that Leibniz isn’t doing metaphysics here, but supporting an ethical point that memory is needed for one to be a fit subject for reward and punishment and a theological point that eternal life requires more than mere eternal existence without the psychological features of human life. Nonetheless, some have thought that thought experiments like Leibniz’s offer support for memory theories of personal identity. I will argue that tweaking Leibniz’s thought experiment in two ways shows that this employment would be mistaken. In fact, I think the second tweak will offer an argument against memory theories.

Tweak 1: Memory theories of personal identity require a chain of memories, but not a chain of personally important memories. So all we need to ensure identity of the earlier individual with the later King of China is that the King of China remembers something really minor from the hour before the transformation, say seeing a fly buzzing around. Allowing the memory of a fly to survive the enthronement does not affect the intuition that the process is one that “the individual has no reason to desire.” The loss of personally important memories—especially of interpersonal relationships—is too high a price for the alleged benefit of ruling a great nation. Hence the intuition is not about personal identity, but—as Leibniz himself thinks—about prudential connections in a person’s life. Nor should we modify memory theories of personal identity to require the memories to be personally important, since that would make personal identity too fragile.

Tweak 2: First, suppose that in addition to the individual’s memories being wiped, the individual gets a new set of memories implanted, copied from some other living person. That so far does not affect the intuition that the process is one that one has “no reason to desire.” Second, add that the other living person happens to be one’s exact duplicate from Duplicate Earth. On memory theories of personal identity, one still perishes—the memories aren’t one’s own, even if they are exactly like one’s own. But a good chunk of the force of the thought experiment evaporates. It is, admittedly, an important thing that one’s apparent memories be real memories, and when they are taken from one’s exact duplicate, they are not. If one’s apparent memories are from one’s duplicate, then one isn’t remembering one’s friends and family, but instead is having quasi-memories of the duplicate’s friends and family, who happen to be exactly like one’s own. That is a real loss objectively speaking. But it is a much lesser loss than if one’s memories are simply wiped or replaced by those of a non-duplicate.

Note further that in the case where one’s memories are replaced by those of a duplicate, if enough benefits are thrown into the King of China scenario, the whole thing might actually become positively worthwhile. Suppose you are a lonely individual without significant personal relationships, but as King of China you would have a fuller and more interpersonally fulfilling life, despite the inevitable presence of flatterers and the mind-numbing work of ruling a vast empire. Or suppose creditors are hounding you night and day. Or you have a disease that can only be cured with the resources of a vast empire. When we note this, we see that the modified thought experiment provides evidence against the memory theory. For on the memory theory, it makes no difference to one’s identity whether the memories will come from a duplicate or not, as long as they don’t come from oneself, and what benefits the King of China will receive is largely prudentially irrelevant.

Objection 1: If the King of China gets memories from your duplicate, then the King of China will have your values and will promote your goals with all of the power of an empire. That could be prudentially worth it and provides some noise for the tweaked thought experiment.

Response: We can control for this noise. Distinguish your goals into two classes: those where your existence is essential to the goal and those where your existence is at most incidental to the goal. We can now suppose that you are a selfish individual who has no goals of the second type. Or we can suppose that all your goals of the second type are such that you think that being King of China will not actually help with them. (Perhaps world peace is a goal of yours, but like Tolstoy you think individuals, including emperors, are irrelevant to such goals.)

Objection 2: If you know that the duplicate has the exact same memories as you do, then copying memories from the duplicate at your behest maintains a counterfactual connection between the final memory state and your pre-transformation memories. If the latter were different from what they are, you wouldn’t have agreed to the copying.

Response: There is nothing in Leibniz’s thought experiment about your consent. We can suppose this just happens to you. And that it is a complete coincidence that the subject from whom memories are taken and put into you is your duplicate.

The Theotokos and personhood

Catholics and the Orthodox insist that Mary is the Theotokos—the Godbearer. The child in her womb was God.

It follows that this child she bore in her womb was a person. For the child was God by virtue of the Incarnation, and the Incarnation consists precisely of the union of two natures in one person. Moreover, the Incarnation is a process of God becoming a human being. So that person in her womb was also a human being.

Thus, the human being Jesus, while in Mary’s womb, was a person. Now, Jesus is like us in all things but sin. So, while we are in our mothers’ wombs, we already are persons.

A theory of personhood or personal identity that requires human persons to have developed human mental functioning—like Warren’s theory of personhood or Locke’s theory of personal identity—conflicts with the Catholic and Orthodox teaching on Mary the Mother of God.

My mother gave birth to me

1. My mother gave birth to me.

2. I have no memory connection, direct or indirect, to me at birth.

3. Therefore, the memory theory of identity is false.

The memory theory of personal identity and the Incarnation

Memory theories of personal identity don’t work for the Incarnation. For Christ’s human mind cannot remember what Christ’s divine mind thought, as it infinitely exceeds the capacity of a human mind.

Objection 1: The Catholic tradition holds that Christ always had the beatific vision. In the beatific vision, the simple God becomes the object of contemplation, and since the simple God is identical with his thoughts, God’s thoughts become the object of contemplation as well.

Response: That’s not memory. And if it were, then memory theories would imply that the blessed in heaven are one person with Christ.

Objection 2: It is not necessary that Christ as human remember Christ’s divine thoughts, but only that Christ as divine see Christ’s human thoughts.

Response: If Christ’s divinely seeing Christ’s thoughts makes for an identity of persons, then absurdly God is also identical with all of us, since God sees all our thoughts.

Objection 3: Memory theories concern identity across time. But Christ’s human and divine natures exist at the same time, if God is omnitemporally eternal, or Christ’s human nature exists in time and the divine nature exists outside of time. In neither case does we have identity across time, and so the memory theory of diachronic identity is unaffected.

Response: If God is omnitemporally eternal, we have another counterexample. Orthodox theology holds that there is one divine mind. Thus, the Son’s thoughts at t₁ the Father’s thoughts at t₁, and hence what the Father remembers at t₂ of what he had thought at t₁ is just as much a memory of what the Son had thought at t₁, which implies the heretical conclusion that the Father at t₂ is identical with the Son at t₁. So, the suggestion in the objection only has a hope if God is outside of time.

Next observe Christ is like us in all things but sin. In particular, he is as capable of amnesia as we are. Suppose Christ suffered amnesia at t₂, so that at at a later time t₃ he did not remember what he thought at an earlier time t₁. But the metaphysical bond between the divine nature and the human nature would surely not be broken by amnesia. So the human being named “Jesus” at t₃ would be the same person as the Second Person of the Trinity, and the human being named “Jesus” at t₁ would also be the same person as the Second Person of the Trinity. Thus, by symmetry and transitivity of identity, the human being named “Jesus” at t₃ would be the same person as the human being named “Jesus” at t₁, despite there being no memory connection, and hence contradicting the memory theory of personal identity.

Perhaps, though, it can be claimed that the Incarnation would of logical necessity be terminated by amnesia. But surely if the Incarnation were terminated, the Second Person of the Trinity could become incarnate once again. In this subsequent incarnation there need be no memories of the first incarnation. Yet if the first-incarnate Son were the same person as the Second Person of the Trinity, and the second-incarnate Son were the same person as the Second Person of the Trinity, it would follow that the first-incarnate Son would be the same person as the second-incarnate Son, once again leading to a case of diachronic identity that contradicts the memory theory of personal identity.

Knowledge of qualia

Consider our old friend Mary, who grew up in a black and white room, learned all of physics, and then saw a red tomato, allegedly learning a new fact about the world, what red looks like. Suppose Mary now went back to her black and white room and returned to contemplating the foundations of quantum mechanics, just as she did before. At that point, clearly Mary knows what red looks like. But unless she is visualizing red stuff, she is not having any red qualia at that point. So:

1. One can know what red is like without having any red qualia.

Moreover, presumably whatever state her mind has—regardless of whether the mind is physical or not—in her black and white room after seeing the red tomato is a state that could have been induced in her (by a neurosurgeon or a demon) without her having had any red qualia. One might worry whether that induced state would count as knowledge, but if one adds that she gets testimonial evidence that her mental representations of qualia are correct despite based on false memories, it could be knowledge. Thus:

2. One can know what red is like without having or having had any red qualia.

It is possible to agree to (2) while holding that the knowledge of qualia argument against physicalism is a good argument. For one might hold that the state of mind that allows for (2) is not a state that can simply come from learning all the physical facts. It is a state that might require some kind of neurosurgical or supernatural intervention. But it seems to me that when one accepts (2), it becomes significantly less plausible that one cannot learn what red is like just by learning all the physical facts.

There is another move the defender of the knowledge argument can make. They can deny (1) and (2), holding that when Mary is back to thinking about quantum mechanics, she doesn’t know what red is like, but that we are inclined to incorrectly say that she knows it because she has the skill of coming to know it at a moment’s notice by visualizing something red. This is a good move, but it has a pitfall: it makes knowledge of what red is like significantly disanalogous to ordinary knowledge, such as of multiplication tables, which one has even when it is merely dispositional, when one is not thinking about it. But if knowledge of what is red is like has this significant disanalogy to ordinary knowledge, that makes it less likely that it is factual knowledge—which the argument requires it to be.

Heaven, the goods of others and the defeat of evil

There is a delight in competing athletically with one’s child: if they win, it feels good, and if one wins, it feels good, too. (The hedonic ideal is achieved when the child wins about 60% of the time; then one feels proud of their superiority, but not rarely one has the pleasure of beating a stronger opponent.)

Parental love makes it easy to love another as oneself (to paraphrase what C. S. Lewis says about Eros). It thus gives us an image of what it is like to be in heaven: we will greatly enjoy the goods had by others. This gives us an attractive picture of how the joy of heaven could fit with enduring differences in personal characteristics. Perhaps being an extrovert would not be true to my self and to God’s vocation for me, and so maybe even over an eternity in heaven I won’t be extroverted. But if so, I will still be fully happy for the joy of the heavenly extroverts, without any regret that I am not one of them, while they will be fully happy for me introverted joys, also without any regret that they are not like me.

Here are two controversial (for very different reasons) applications of this. First, there is a genuine and distinctive good in being a woman and there is a genuine and distinctive good in being a man, and it seems to make sense for a person to desire the goods of the other sex, regardless of whether it is possible to have them oneself. In heaven, however, Joseph can enjoy Mary’s good in being a woman and Mary can enjoy Joseph’s good in being a man, without Joseph regretting that he personally “only” has the good of manhood and Mary regretting that she personally “only” has the good of womanhood. That is what total love is like.

Second, given an eternalist or moving block theory of time, the past will always be fully real. This in turn gives us a solution to the problem that various important goods, such as marriage and self-sacrifice, will not be available in heaven. For we will be able to rejoice in others’ past possession of these goods, without regret for the fact that they aren’t ours and now.

The second point, however, raises the following problem: Won’t we also grieve for others’ past—and even present, if hell is a reality (as I think it is)—subjection to great evils? Maybe, but in God’s plan there is a crucial asymmetry between good and evil. Evils are defeated. How this defeat happens is deeply mysterious. But because of this defeat, I suspect the grief for a defeated evil will not hurt, precisely because of the evil’s being defeated, while goods remain undefeated and hence the joy for them will always delight.

In fact, the last point suggests something to me. A lot of philosophers of religion have said that it’s not enough for theodicy if evils are justly compensated for or their permission is in some way justified. We need these evils to be defeated. I think this is mistaken if all we are after is a response to the problem of evil. But we also need a response to the problem of why the past and present suffering of others doesn’t cause the saints pain in heaven. And it is here that we need the defeat of evil.

Another really weird thought experiment

Suppose we accept a memory theory of personal identity and accept that people can be moved from one set of hardware to another. Now suppose Alice is an internally determinstic person, currently without inputs from the outside world, whose mental state is constantly backed up to a hard drive. Suppose now that Alice is a person who in hardware AliceOne has experiences E₀, E₁, E₂, E₃ at times 0,1,2,3, respectively. Then the initial hardware is destroyed, and the backup from just before time 2 is restored into another piece of hardware, AliceTwo, who goes on to have experience E₂. Then AliceTwo is destroyed, and a backup from just before time 1 is restored into AliceThree, who goes on to have experience E₁, after which all the hardware and the backups are destroyed by a natural disaster.

What is the order of Alice’s experiences? The obvious answer is:

• E₀, E₁, E₂, E₃, E₂, E₁ at times 0−5, respectively.

In particular, when Alice is experiencing E₂ for the second time, if she were informed of what is going to happen, she would be rationally dreading E₁ if E₁ is unpleasant. For E₁ would be in her future.

What makes it be the case that the second E₁ is experienced after the second E₂? It is the order of external time, according to which the second E₁ comes after the second E₂. It is not the order of causal connections in Alice (since the second E₂ comes from first E₁ while the second E₁ comes from the first E₀, and since there need be no causal connection between the hardware AliceTwo and AliceThree).

I think this is all a bit odd. To make it odder, let’s imagine that AliceTwo and AliceThree are in a room that time-travels in such a way that it is first at time 5 and then at time 4. Now, perhaps, Alice experiences the final E₁ before she experiences the final E₂. That’s really unclear, though.

The more I think about various combinations of time-traveling backups and time-traveling hardware, the more indeterminate it looks to me whether the final E₂ comes before the final E₁.

This is not much of an argument. But the above lines of thought lead me to think that one or more of the following is true:

1. Time travel is impossible.

2. People cannot be moved from one piece of hardware to another.

3. One does not survive restoration from a backup.

4. The order of experience does not have tight connections to rationality of attitudes.

5. The order of experience can be quite indeterminate.

Partial amnesia and fission

Some cases of partial amnesia present a prima facie problem for memory theories of personal identity (the theorist will bite the bullet on total amnesia, of course). At 9 pm, Bob starts to drink. At 11 pm, he makes a fool of himself. At midnight, he passes out. At 9 am, he wakes up remembering nothing that happened after 10 pm. Obviously, at 9 am, it’s the same person as the one who made a fool of himself the night before, but there is no chain of memories from the 9 am self to the 10 pm self.

There is a simple solution: don’t talk about chains of memories, but instead talk of chains of memory-links. Memories are unidirectional (you remember later what happened earlier) but memory-links are bidirectional: when at t₂ you remember what happened at t₁, there is a memory link from t₁ to t₂ as well as from t₂ to t₁. And now we have a chain of memory links: the morning-after self is memory linked to the 9 pm night-before self, and the 9 pm night-before self is linked to the 11 pm night-before self (Bob at 11 pm remembers starting to drink at 9 pm). So the morning-after self is the same as the 11 pm night-before self, much as he might wish he weren’t.

But here is an interesting thing. If we think about this scenario, formally this is a case of fission. There are two memory branches:

1. starting at 9 pm, then going on to 10 pm, 11 pm, and up to midnight, and then fizzling out forever

2. starting at 9 pm, then going on for a little bit, then skipping until 9 am.

So, partial amnesia cases like the above are actually cases of fission. And in cases of fission, most people do not want to say that we have the same person in the two branches. The most popular solution is that fission is death, and a second option is a four-dimensionalist one on which the occurrence of fission shows that there were two people there all along. But neither option is plausible for our partial amnesia case. It is absurd to say that Bob automatically dies around between 9 and 11 pm. And it is absurd to say that there used to be two people in Bob’s body all along. Those are extreme solutions that might fit science-fictional cases, but surely are not appropriate for all-too-common cases like Bob’s.

Perhaps we can say this: real fission requires there to be two simultaneous branches. So now our theory is this:

3. when memories branch, and the two branches are simultaneous, then something metaphysically weird happens (either there were two people before the branching or the pre-branching person has died).

But (3) fails in time-travel cases. Suppose Bob owns a time-machine. At 9 pm, Bob goes into a time-machine set for midnight. He keeps on drinking in the machine for two more hours, until 2 am. Then he passes out and loses the memory of the last two hours of drinking while the time-machines auto-pilot pulls him back to midnight and dumps him in his bed. We now have two branches starting at midnight: Bob drinking in the time-machine for two hours and Bob sleeping in bed with loss of memory of two hours of drinking. But it seems wrong to say that by adding a time-machine to the original partial-amnesia story, thereby making the two branches simultaneous, we would get the weirdness of having Bob perish or having always had two persons there.

Suppose you think backwards time-travel is impossible because of the paradoxes that result. You should still think of forwards time-travel as possible. Indeed, non-instaneous forwards time-travel is possible: that’s what happens in the twin paradox from relativity theory. But there is nothing logically absurd about instantaneous forwards time-travel. But any case of simultaneous-branch fission can be transformed into a case of non-simultaneous-branch fission by forward traveling one branch right after branching to a future time after the other branch has perished. Thus, we really shouldn’t treat simultaneous and non-simultaneous branchings differently.

I think this is a serious problem for memory theories of personal identity.

Causation and memory theories of personal identity

Unlike soul-based theories, the memory, brain and body theories of personal identity are subject to fusion cases. There are four options as to what happens when persons merge:

• Singleton: a specific person continues, but we don’t know which one

• Double Identity: there was only one person prior to the fusion, wholly present in two places at once

• Scattered: there was only one person prior to the fusion, half of whom was present in one location and half of whom was present in another

• End: fusion causes the person’s demise and the arising of a new person.

The problem with Singleton is that it supposes there is a fact about personal identity deeper than facts about memories, brain-continuity and body-continuity, which undercuts the motivation for the three theories of personal identity.

Double Identity and Scattered are weird. Moreover, it leads to absurdity. For whether you and I are now one person or two depends on whether we will in fact fuse in the future, and we have backwards counterfactuals like: “If you and I fuse, then we will have always been one person.” This is just wrong: facts about your being a different person from me should not depend on what will happen. And consider that if you and I decide to fuse, thereby ensuring that we have always been one person J, either bilocated or scattered, then J exists because of J’s decision to fuse. But an individual cannot exist because of a decision made by that very individual.

That leaves End. I think End may be a good move for brain and body theorists. But it’s not a good move for memory theorists. For by analogy, we will have to say that fission causes a person’s demise, too. But then it is possible to kill a person without any causal interaction. For suppose you are unconscious and undergoing brain surgery under Dr. Kowalska. Dr. Kowalska scans your brain to a hard drive as a backup. A malefactor steals the hard drive from her as well as a blank lab-grown brain. If the thief restores the data from the hard drive into the lab-grown brain, that will result in fission and thus death. But the thief’s restoring of the data into the blank brain is something that can happen without any causal interaction with you. Hence, the thief can kill you without causally interacting with you, which is absurd.

Hence both Double Identity and End have causality problems on the memory theory: Double Identity allows someone to be literally self-made and End allows for killing without causation. It may be that if one is less of a realist about causation, these problems are less, but since memory itself is a causal process, it may be that memory theories of personal identity don’t sit well with being less of a realist about causation.

Naturalism and second-order experiences

My colleague Todd Buras has inspired this argument:

1. A veridical experience of an event is caused by the event.
2. Sometimes a human being is veridically experiencing that she has some experience E at all the times at which E is occurring.
3. If (1) and (2), then there is intra-mental simultaneous event causation.
4. If naturalism about the human mind is true, there is no intra-mental simultaneous causation.
5. So, naturalism about the human mind is not true.

In this argument, (4) is a posteriori: if naturalism is true, mental activity occurs at best at the speed of light. I am sceptical about (2) myself.

Living on in people's memories

There is a philosophical (in the popular sense of the word--professional philosophers don't tend to defend this) outlook on death that says that we live on in people's memories of us. I was discussing this view with students in my Death and Afterlife class, and one of them connected this to the memory theory of personal identity. My first reaction was that this was completely confused. But after reflection, I thought that there was a deep point about the memory theory of personal identity there.

Start by observing how unsatisfying this kind of "afterlife" in people's memories is--it's not really "living on". Now, the student's potential confusion was that on canonical versions of the memory theory of personal identity, we live on through a chain of first-person memories, while the memories through which we are said to live on are third-person ones. But does that point matter? Suppose one or more of the people through whose memories I was said to live on actually managed to acquire first-person (apparent) episodic memory of my life, say by thinking about me so much. That's a bit creepy, but it's no more satisfying as an afterlife than when the memories were third-person.

Of course the proponent of the memory theory can say I am unfair. The memory theory requires that there be only a single person with those memories, and it has restrictions on what sort of causal chain is allowed to pass the memories on. But these matters of detail do not, I think, affect whether I am living on in any robust sense through a person who has memories of my life.

Personal identity, memory and fission

Suppose that (a) memory connections are constitutive of personal identity and (b) fission of memories destroys a person. If one accepts (a), then (b) is very plausible, so (a) is the crucial assumption.

Now consider this case:

• At 4 pm, due to trauma, Sam suffers complete and irreversible amnesia with respect to events between 2 pm and 4 pm.

Then the 5 pm Sam has first-person memories of the 1 pm Sam, and it seems thus that:

1. The 5 pm Sam is identical with the 1 pm Sam.

But the 3 pm Sam also has first-person memories of the 1 pm Sam, and by the same token:

2. The 3 pm Sam is identical with the 1 pm Sam.

By symmetry and transitivity:

3. The 3 pm Sam is identical with the 5 pm Sam.

There is as yet no absurdity here. There is, after all, a chain of memory connections between the 3 pm Sam and the 5 pm Sam, though the connections don't run in the same direction (3 pm Sam remembers 1 pm Sam who is remembered by 5 pm Sam). But I think there is a tension between (3) and (b), the claim about fission. For now imagine a different case:

• At 2 pm, Sam's memories are copied into a spare brain, call it Bissam, and Bissam immediately time travels forward to 4 pm. (Forward time travel does not seem metaphysically problematic.) At 4 pm, Sam is killed.

This is clearly a case of fission, and so the 1 pm Sam no longer exists at 5 pm. But in terms of the structure of memories, this case is exactly the same as the initial amnesia case. The 5 pm Bissam remembers (or quasi-remembers, if we want to nitpick) the 1 pm Sam but not the 3 pm Sam. Likewise, in the original story, the 5 pm Sam remembers the 1 pm Sam but not the 3 pm Sam. In both stories the 3 pm Sam remembers the 1 pm Sam. So it seems that in both cases the 5 pm person and the 3 pm person are the results of the fission of the pre-2 pm person. Well, almost. Bissam exists for an instant at 2 pm while the memories are copied into him. But that isn't essential. We could imagine the copying process works such that the memories are only fully seated once Bissam arrives at 4 pm.

So the memory theorist who thinks that fission kills a person should think that total amnesia with respect to a short time period also kills one.

But if that's right, then we don't survive those nights where we do not remember our dreams upon waking up. For the dreaming person has memories (skill memories at least; but also temporarily inaccessible episodic memories) of the person who went to bed. But the waking person doesn't have memories of the dreaming person, though she does have memories of the person who went to bed. So the person who went to bed fissions into the person who dreams and the person who wakes up.

This means that the memory theorist shouldn't think that fission kills. (Another standard argument for this conclusion: If fission kills and identity is constituted by memory, then you can be killed by having your brain scanned and the data put into another brain; but you can't be killed by a process that doesn't affect your body.) But if fission doesn't kill, then it seems that the best view is that in cases of fission there have always been two persons. And that leads to various absurdities, too.

Might I be a zombie?

According to epiphenomenalism, qualia—the raw experiential feels—are causally inert. In particular, it seems that my beliefs about qualia are not caused by the qualia, but by the neural correlates of the qualia. But this would lead to the absurd possibility that I might take myself to have exactly the sensory experience I now do—the visual experience as of a computer screen, the auditory experience as of keys tapping and fans running, the tactile experience as of my left leg tucked under me—while having no sensory experiences whatsoever. Moreover, it seems to open up the way for an odd sceptical hypothesis: maybe I am wrong in thinking I am conscious, but actually I am a total zombie!

Maybe the "I am a total zombie" hypothesis isn't an option. For maybe my occurrent beliefs are essentially conscious. Perhaps an occurrent belief is partly constituted by a content-providing neural state and the right as-of-believing quale. So without the qualia, I wouldn't have the beliefs, and in particular I wouldn't believe that I am conscious. So I couldn't be wrong in thinking occurrently I am conscious. Alright, so while the "I am a total zombie" hypothesis can be ruled out, the hypothesis that I am a partial zombie, that I have no sensory qualia but only the as-of-believing qualia, still around, and seems almost as problematic.

Maybe, though, the occurrent belief that I am having a visual experience as of a computer screen is partly constituted not by, or not just by, an as-of-believing quale, but by the qualia of the visual experience. If so, then I can't have the occurrent belief that I am having a visual experience while being a visual zombie.

If we take the above solution, though, we run the danger of violating the platitude that our beliefs cause our actions. For if my occurrent beliefs are partly constituted by qualia, and qualia are causally inefficacious, then it seems that it is not the beliefs but their causally efficacious neural constituents that cause the actions.

I am not sure how much weight to put on this objection to epiphenomenalism. After all, if my car's headlights blind a driver, then my car blinded the driver, even if only derivatively. There is no problem with overdetermination when one of the overdeterminers is derivative from the other. It is, perhaps, a little troubling that our occurrent beliefs only derivatively cause our actions, but that might in fact be just right. For it could be that an occurrent belief is partly constituted by a non-occurrent belief and something—maybe the as-of-believing quale—that makes it occurrent. And then it could be that the associated non-occurrent belief is what causes the action—after all, non-occurrent beliefs certainly do affect our actions.

So the "Might I be a zombie?" objection has fallen. But there is still an objection in the vicinity. My memory of having had experiences is not caused by these experiences. And that is wrong: a memory of A must be caused by A (at least in the derivative kind of way in which even absences are said to cause—I can, after all, remember an absence).

Psychological theories of personal identity and transworld identity

On psychological theories of personal identity, personal identity is constituted by diachronic psychological relations, such as memory or concern. As it stands, the theory is silent on what constitutes transworld identity: what makes person x in world w₁ be the same as person y in world w₂. But let us think about what could be send in the vein of psychological theories about transworld identity.

Perhaps we could say that x in w₁ is the same as y in w₂ provided that x and y have the same earliest psychological states. But now sameness of psychological states is either type-sameness or token-sameness. If it's type-sameness, then we get the absurd conclusion that had your earliest psychological states been just like mine, you would have been me. Moreover, it is surely possible to have a world that contains two people who have the same earliest types of psychological states. But those two people aren't identity.

On the other hand, if we are talking of token-sameness, then we seem to get circularity, since the token-sameness of mental states presupposes the identity of the bearers. But there is a way out of that difficulty for naturalists. The naturalist can say that the mental states are constituted by some underlying physical states of a brain or organism. And she can then say that token-sameness of mental states is defined in terms of the token-sameness of the underlying physical states. This leads to the not implausible conclusion that you couldn't have started your existence with a different brain or organism.

But I think any stories in terms of initial psychological states face the serious difficulty that it is surely possible for me to have been raised completely differently and to have had different initial psychological states. This is obvious if the initial psychological states that count are states of me after the development of the sorts of cognitive functions that many (but not me) take to be definitive of personhood: for such functions develop after about one year of age, and surely I could have had a different life at that point.

In fact this line of thought suggests that no psychological-type relation is necessary for transworld identity. But if no psychological-type relation is necessary for transworld identity, why think it's necessary for intraworld identity?

Remembering your body

Suppose that as I slept, my body has been switched on me in the middle of the night, but all my memories were kept intact. Now it's morning and I have woken up in a new body. But the new body is similar enough to the old that I haven't noticed any difference. My, will I be surprised when I look in the mirror.

I remember going to bed last night. Or do I?

In remembering going to bed, what do I remember? I remember, perhaps, my feeling myself lying bodily in bed. That involves remembering my body as lying in bed.

Which body do I remember lying in bed?

Consider: I remember my body as lying in bed a few seconds ago and I remember my body as lying in bed the previous morning Moreover, there seems to be a univocity to these memories. It is the same body that I remember lying in bed, just as it is the same bed that I remember it lying in. I have no idea that today's body is different from yesterday's body.

Suppose the body I remember lying in bed is yesterday's body in both cases. Then my memeories from a few seconds ago are non-veridical when I remember my body being in bed a few seconds ago. And that doesn't seem right.

Suppose the body I remember lying in bed is today's body in both cases. Then I don't actually remember my body lying in bed yesterday morning: it was a different body that was lying in bed. I am misremembering due to an error of body misidentification.

But if I am misremembering, then my memories must have somehow changed. Last night my memories of yesterday morning were veridical. So at night they must have changed, either in type or in token.

And so the initial description of the story was wrong: I didn't actually switch bodies while keeping all my memories intact.

But perhaps I am wrong when I insist that the body I remember lying in bed a few seconds ago is the same body I remember lying in bed yesterday morning. Perhaps bodies are like clothes: when I remember wearing a blue shirt yesterday and I remember wearing a blue shirt a week ago, there is no particular blue shirt that I remember wearing on both occasions. I just remember wearing some blue shirt or other. Likewise, maybe rather than remembering a particular body as lying in bed yesterday morning, I remember lying in bed yesterday morning in some body or other, and I remember lying in bed this moring in some body or other.

I am not sure that's right. Surely I can remember that yesterday morning I had my phone in this hand, checking my email while awaiting the full return of consciousness. And so there is a particular hand in my memories, the same one that I remember holding my phone in a few seconds ago. And, again, as before this is either yesterday's hand or today's hand. That it's yesterday's hand means that I can't remember which hand I held the phone in a few seocnds ago. That it's today's hand means that I must have lost a memory.

But let's press on this. Can't the same thing happen with clothes? Say I remember wearing this very shirt last week, the one I am wearing now. But suppose my wife has switched it on me in the meanwhile. Surely a switch of shirts doesn't imply a loss of memory. But which memory is mistaken? My memory of wearing this shirt last week or my memory of wearing it now? Neither, perhaps. I remember wearing this shirt a few seconds ago. I remember wearing that shirt last week. But I don't remember wearing this shirt last week—though I may say I do. What I remember is wearing a shirt like this.

Can I make the same move with hands? I don't remember holding the phone in this hand. I simply remember holding the phone in a hand like this—most notably, like it in respect of chirality and connection to my mind. Still, I think it gets the phenomenology wrong.

So, if I'm right, the hypothesis of changing bodies while keeping all memories is a dubious one. Our autobiographical memories are bound up with our bodies—just as we enter de re into our autobiographical memories, so do our bodies.

Could I, though, switch bodies and keep a core of autobiographical memories? I am not sure. Core autobiographical memories seem to be closely bound up with embodiment. We can abstract from the particulars of embodiment, but when we abstract from a memory what we get need not be a memory any more. I remember lying in bed last night in some body or other, I say. But that's an abstraction from what I actually remember, perhaps—I remember lying on my back—this back—with a pressure sensation in my hand—this hand—from the phone that I am holding in it while checking my email. That's the memory.

Is this fatal to psychological theories of personal identity? Maybe not: maybe only to ones that are focused on autobiographical memories.

I am not entirely convinced by this argument, but I think it has some force.