The psychological theory of personal identity

Let's suppose that personal identity over time is secured by continuation of psychological states. Now imagine Jim and Sally are robots who are persons (if you don't think robots could be persons, just suspend disbelief for a while until I get back to the issue) and have almost all of their psychological states on their hard drives. According to the psychological theory, if you swap Jim and Sally's hard drives, Jim and Sally will go with the hard drives, rather than with the rest of their hardware. But here is something odd. When you unplug Jim and Sally's hard drives during the swap, either Jim and Sally continue existing or they don't. If they do continue existing, then by the psychological theory, they are surely located where the hard drives are, since that's where the memories are. They are basically reduced to hard drives.

There is a case to be made that they do continue existing, at least given the psychological theory of personal identity. First: To kill an innocent person, even temporarily (after all, many people, including me, believe that all our deaths are temporary!), is seriously wrong. But swapping hard drives doesn't seem problematic in this way. Second: There is some reason to think temporally gappy existence is impossible, and if gappy existence is impossible, then if Jim and Sally exist before and after the swap, they exist during it. Third (and specifically to the psychological theory): It is plausible that if the identity of a person across time is secured by a part of the person, then the person can exist reduced to that part. Thus, if the identity of a person comes from the soul, then the person can survive reduced to a soul.

So we have this: Given the psychological theory, Jim and Sally exist reduced to hard drives. But that's absurd! For we can replace hard drives by cruder mechanisms. We can suppose a computer where memory is constituted by writing in a large book. It is absurd to think a person can exist reduced to a book. So we should reject the psychological theory.

Well, that assumed that robots could be persons. Maybe they can't. And our memories do not sit on a convenient isolated piece of hardware in the brain. Indeed, that is true. But surely agents could have evolved whose memories are stored on a convenient isolated piece of hardware, and such agents could be persons. And the argument could be run for them.

People are not fungible

If people are fungible—can be exchanged for exact duplicates without this making any significant difference of value—then any two situations where there is the same number of exactly similar people are equivalent in value. After all, we can get from one situation to the other by just replacing the people in the one situation by the people in the other.

But suppose there are infinitely many exactly similar happy people and every second one ceases to exist. Obviously, something bad has happened—a lot of value has gone out of the world. But the number of exactly similar happy people is the same. So people are not fungible.

Two kinds of fungibility

I was teaching Jennifer Whiting's "Impersonal Friends" this morning—I love that piece—and I was going into the usual distinction between the fungible and nonfungible. I generally illustrate this with heirlooms. While money is fungible, the ring inherited from great grandmother is not: if the ring were swapped out for another just like it, it wouldn't be as good.

As I was teaching, though, I realized that that's too quick. Suppose that in the first place great grandmother instead had a different but similar ring and it was passed down through the generations to us. That would make no difference to anything that matters to us. So the ring is broadly fungible: it can be swapped for another ring with relevantly similar historical properties. The same seems true of all heirlooms.

But are persons fungible in the same way? Here's a thought. If something rightly matters a great deal to me it matters objectively at least somewhat. It rightly matters a great deal to me that I exist. It thus rightly matters a great deal to me that all of my history wasn't swapped for that of another similar individual. Therefore it matters objectively at least somewhat. Hence I am objectively not fungible even in that broader sense.

More on fungibility and naturalism

In an earlier post, I argued against materialism on the grounds that persons are non-fungible but material objects are fungible or at least persons are non-derivatively non-fungible, while material objects are at best derivatively non-fungible.

Here's a pathway to arguing that if naturalism is true, then at least some persons are fungible. Since no persons are fungible, it follows that naturalism is false.

Start with the thought that:

1. Something wholly composed of fungible parts is fungible.

If this is right, and material objects are composed of elementary particles, then all material objects are fungible since elementary particles are fungible. And that's all we need for our argument.

But (1) may not be quite right. After all, arguably, the Mona Lisa is (derivatively) non-fungible, but all the elementary particles making it up are. There would be no loss if we replaced the particles of the Mona Lisa one by one. The non-fungibility of the Mona Lisa is grounded in the non-fungibility of the arrangement of the parts: If suddenly the Mona Lisa was burnt up, but by coincidence the particles in the ashes and smoke arranged themselves in an exactly similar arrangement, something of value would be lost. There is something special here about the arrangement.

What makes the arrangement of the Mona Lisa's particles special is the specialness of the artistic process that produced that arrangement. This suggests:

2. Something wholly composed of fungible parts arranged by a fungible process is fungible.

A fungible process is one such that it is value-relevant whether it is replaced by an exact copy. The painting of the Mona Lisa is like that. Given (2), it is very plausible that things composed of fungible parts are at best derivatively non-fungible, with their non-fungibility derived from that of the process of generation.

Now you or I perhaps did have our parts get arranged by a non-fungible process: our parents' loving union. But even persons produced by in-vitro fertilization had their parts arranged by our biological parents' bodies through their gametes, and the process of gamete production in a person is arguably non-fungible.

However, at least one person—namely, a first human person—has no person as a biological parent, on pain of an infinite regress. If theism is true, that person may still be the product of a non-fungible process of creation by a (divine) person. But naturalism rules out not only dualism but also theism. A naturalist who does not believe in an infinite past will have to hold that there is a first person who is in no way produced by a person. And there it seems that the process producing that first person is fungible—it plausibly doesn't matter value-wise which of two exactly similar brute animals mated with a brute animal to produce a person. (If it is responded that primates like those we descend from are themselves non-fungible, then just take the argument further back in our evolutionary past.)

Fungibility, persons and materiality

This seems plausible:

1. All purely material objects are fungible.
2. No persons are fungible.
3. So, no persons are purely material objects.

Maybe that's not quite right. One might think that some objects care about (a colleague gave the examples of the Mona Lisa and Grandpa's Bible) are non-fungible. But I think it's plausible that material objects are at most derivatively non-fungible, deriving their non-fungibility from the non-fungibility of people. Thus:

4. No purely material object is non-derivately non-fungible.
5. Every person is non-derivatively non-fungible.
6. So, no person is a purely material object.

A (paradoxical?) argument that intentional reproduction is wrong

Consider:

1. We cannot permissibly intend to produce a person for reasons that do not include the specific person's own good.
2. We cannot intend to produce a person for reasons that include the specific person's own good.
3. We cannot permissibly intend to produce a person without reasons.
4. Necessarily, if we intend to produce a person, we do so for no reason, or for reasons that include the person's own good, or for reasons that do not include the person's own good.
5. We cannot permissibly intend to produce a person. (1-4)

Premise (1) is due to Kantian considerations: persons are ends not means. I will argue for premise (2) shortly. Perhaps the easiest way to argue for premise (3) is that we simply cannot intend—permissibly or not—without reasons. We intend things because they are good, either as means or as ends, and in either case we have reasons. But one might also argue that if it is wrong to produce persons for reasons that do not include the person's own good, it is a fortiori wrong to produce them wantonly, for no reason at all, as it were on a whim. Or one might think that being rational animals, it is wrong for us to intentionally act in a non-reasnable way, and to act intentionally but without reasons is to do that.

Now on its face, premise (2) is false. Surely people do procreate for the child's own good. But I don't think so. They may be acting for the good of whatever child results from the reproduction, but there is no specific child for whose good they are acting. And when they act for the good of whatever child results, the specific child's good ends up being a constitutive means to the good they are seeking, so they do not escape from the Kantian criticism. The good of a person is an incommunicable good: it is that specific person's good. But the existence and identity of the child depends on the couple's decision in a way that the couple is unable to figure out beforehand. Thus the couple cannot be deciding in light of the identity of the child, and hence cannot be acting for the good of that specific person.

Note that God does not suffer from the cognitive limitations that give rise to (2): he can know our identity before he decides to create us, and can decide to create us for our own good.

Now, when a couple engages in the marital act, they have a reason to engage in that act apart from reproduction: the act is good in itself, being an embodiment of marital union. Thus they can act so as to unite, and accept the child as a gift from God that goes beyond their intention. Note that even given my argument they can permissibly rationally consider the reproduction in their decision whether to make love, for instance as a defeater to various defeaters (being tired, etc.) to the marital reasons for lovemaking. On the other hand, in non-coital methods of reproduction like IVF the couple is specifically intending reproduction, and that is wrong if the argument succeeds.

I am not myself entirely convinced of (1), because I am not entirely convinced of the Kantian autonomy framework. We aren't ends in ourselves: we exist as constitutive glorifications of God. Thus it does not seem contrary to the dignity of a person to be produced for the greater glory of God. Kantianism is what you get when you remove God from the story. If that's right, then we get the surprising result that only theists can permissibly intend to produce a child. Atheists, to be consistent, will need to have the Kantian attitude, and while they can permissibly reproduce, they cannot do so with the intention of reproducing, if everything else in the argument works.

The most fundamental and what matters most

What matters most are things like people, love, understanding, courage, friendship, beauty, etc. According to many contemporary metaphysicians, what is most fundamental are things like sets, points, photons, charge, spin, the electromagnetic field, etc. It's almost as if the metaphysicians took the fact that something matters to be evidence that it isn't fundamental.

But here is a plausible hypothesis or at least heuristic:

• Fundamental predicates apply primarily to fundamental entities, and derivatively to other entities.

While a table can have mass or be charged, it has mass or is charged derivatively. It is particles that primarily have mass or are charged. Now, some value predicates like "matters" or "is valuable" are fundamental. (Of course, this is the controversial assumption.) Thus we have reason to think the kinds of things they primarily apply to are themselves fundamental, and they apply only derivatively to non-fundamental things. But the value of a person is not derivative from the value of the person's constituents like fields or particles, and the way in which a person matters does not derive from the ways in which fields or particles matter.

Thus, either persons will be themselves fundamental, and primary bearers of value, or else persons will be partly constituted by something fundamental which is a primary bearer of value. The best candidate for this valuable constituent is the soul. Hence, either persons are fundamental or they have souls that are fundamental.

In fact, I would conjecture that we should turn on its head the correlation between fundamentality and not mattering that we find in much contemporary metaphysics. The more something matters, the more reason we have to think it is fundamental, I suspect. This may lead to a metaphysics on which there are fundamental facts about persons, their psychology and their biology, a realist metaphysics with a human face.

Might "animal" be a stage term?

Consider this argument:

1. It is possible for me to exist disembodied.
2. It is not possible for an animal to exist disembodied.
3. So, I am not an animal.

While I accept (1), I am not convinced of (2). However I want to try a somewhat different tack in this post. Compare:

4. It is possible for Tom Brady to exist disembodied.
5. It is not possible for a football player to exist disembodied.
6. So, Tom Brady is not a football player.

But (6) is false (or so I understand from one website). And even if (4) were false, we shouldn't be able to derive its falsity simply from (5) and the fact that Tom Brady is a football player. So there has to be something wrong with the second argument. And the diagnosis is very simple: "football player" is a stage term. An entity can exist at one time as not a football player and at another time as a football player. Thus, (5) is ambiguous between two claims:

• It is not possible for someone who is presently a football player to exist disembodied at any time.
• It is not possible for someone to exist disembodied while being a football player.

The second of these may be true[note 1] but it is insufficient for deriving (6) from (4)—it only implies that Tom Brady can't be football player when disembodied, not that he can't exist when disembodied. And the first reading simply begs the question.

Why not draw the same conclusion from the first argument? Granted (I am not sure of this) one can't be disembodied while being an animal. But why can't someone who is an animal at one time be disembodied at another time, ceasing to be an animal then? Then "animal" would be a stage term. (It could even be the case that "animal" is a stage term while "person" isn't.)

If animalism is the claim that we are animals, then this would be compatible with animalism. One couldn't, however, straightforwardly say that we are essentially animals. But one could say that it is an essential property of beings like us that they begin their existence as animals, or at least (maybe God could create someone already in the disembodied stage?) that they normally do so.

One could say that these are claims about all animals or just about rational ones. Maybe only some animals—say, the rational ones—have the capability of becoming disembodied souls.

Two arguments for extended simples

A simple is something that lacks proper parts. An extended simple is a simple that occupies a region of space that is more than a point.

1. If I am not simple, then I think with a proper part of me.
2. I do not think with a proper part of me.
3. So, I am a simple.
4. I am extended.
5. So, I am an extended simple.
6. So, there is an extended simple.

The thought behind (1) is that if I am not simple, then my brain and/or my soul are going to be parts of me in the true ontology, and surely if the true ontology contains them, then I think with them. The thought behind (2) is that if A is a proper part of B, and I think with A, then A is a better candidate than B for being me. And (4) follows from the fact that I am 182 cm tall.

While I am inclined to accept (6), I find the argument for (2) weak. I would find it stronger if one could conclude from the fact that I think with A that A thinks, but I don't see that that follows.

Maybe a better argument:

7. No particle occupies just one point.
8. All particles occupy space.
9. Some particles are simple.
10. Something that occupies space but does not occupy just one point is extended.
11. So, there is an extended simple.

The thought behind (7) is that in real life no particle has a wavefunction that is concentrated at one point.

Here, I am actually not sure of (10).

Not only am I myself, but I am my self

1. (Premise) I am experiencing writing this post.
2. (Premise) My self is experiencing writing this post.
3. (Premise) Only one entity is experiencing writing this post.
4. So, I am my self.

This is an oblique partial Olsonesque response to a paper by Himma. It's not fully a response.

Values, persons and wholes

Start with these premises:

1. Value personalism: Nothing is more valuable than a good person except perhaps for another good person.
2. If A has finite value and B has positive value, and the mereological sum A+B exists, then the mereological sum A+B has more value than A.

Thus, it is not possible to have a mereological sum of a finitely valuable good person, say Socrates, and one or more (the "or more" will use transitivity of "is more valuable than") positively valuable objects, say frogs or oak trees, unless the sum is a person. But whether things compose a whole shouldn't depend on their values. Thus it is not possible to have a mereological sum of a finite person and one or more things, unless the sum is a person.

So, if there are mereological sums, finite persons are not a part of them, unless the sums themselves are persons. But it would be weird if it were possible for finite persons to be proper parts of mereological sums that are persons but not of other mereological sums. So it is reasonable to conclude that finite persons can't be proper parts of mereological sums. But neither can God be a proper part of any mereological sum. So, no person can be a proper part of a mereological sum.

I think the best explanation of all these facts is that there can't be such a thing as a mereological sum.

Another argument against gear-minds

Here's another argument against gear-minds. Start with the intuition that one cannot make a mind cease to exist without causally interacting with the individual whose mind it is or a part of the individual. Now imagine that the gears that the mind is made of are like those in this diagram . They have radiating spokes, and between the spokes is a hollow area. This reduces the weight of the gear while maintaining a significant portion of the strength.

Now, imagine that an inflexible spike is simultaneously inserted into the middle of every gap between spokes, without the spike touching any gear. Because the gears are no longer able to turn more than, say, a sixth of a rotation, and because any mental operation would surely require a larger turn of at least one wheel (we can stipulate this about our gear-person), a result of the introduction of the spikes is that the individual is no longer capable of any mental functioning. The gears can turn a little, but not enough to result in a mental operation. Moreover, no counterfactuals of the form "If input A were given, the individual would believe Q" are true any more. This means that if the functionalism requires such counterfactuals or the capability of mental functioning, as non-Aristotelian functionalisms are apt to require, there is no longer a mind. But because the spikes went between the spokes in such a way that no contact was made with any part of the individual, this violates the principle that one cannot make a mind cease to exist without causally interacting with the individual or a part thereof.

Could something made of gears be a person?

Leibniz offers as a reductio of materialism the idea that if materialism is true, one could have a mind whose functional parts are like the parts of a giant mill, and you could walk right through that giant mill, seeing big wheels of all sorts. But, he thinks, you'd never meet with consciousness.

Leibniz's argument has two parts:

1. If materialism is true, a mind could be made of large gears (together with some source of kinetic energy, like a large water wheel).
2. A mind could not be made of large gears (plus energy source).

I think step (1) can be backed up as follows:

3. If materialism is true, functionalism is true.
4. If functionalism is true, then any physical system that can do sufficiently complex computations can be a mind.
5. A system of large gears (with an energy source) can do arbitrarily complex computations.
6. Therefore, (1) holds.

Leibniz doesn't do much to back up (2). The purpose of this post, and perhaps some succeeding ones, is to try to do this.

Here's one approach. If a mind could be made of gears, so could a person. Imagine a person made of hard plastic gears. Moreover, every so often the gears are given a rest (maybe so they can cool off—we don't want them to melt)—a small clockwork contraption disconnects the energy source, and everything, except that clock, becomes motionless. Now, a person exists while asleep, and it's plausible that in the rest state, the person would still exist.

Scenario 1: The whole set of gears, but not the wake-up clock, is in a big closed box, and while the gear-person is in a rest state, a thin slow-set two-part epoxy is poured into the box. It turns out that the person could still function with the epoxy, because the source of energy is powerful enough to move the gears through the liquid. However, slowly, the epoxy sets. Within 24 hours, what we have in the box is basically a single solid chunk (if we like, we can imagine the gears were themselves made of the same kind of epoxy, and then maybe one can't even tell where the gears were—but Scenario 2 won't work in that case). A single solid chunk like that isn't a person. So, during the 24 hour epoxy curing process, the person gradually ceases to exist. If we believe there cannot be vague existence, then that's enough to yield absurdity: persons can't cease to exist gradually. But it would be absurd if some slight change in the set of the epoxy were to make the difference between existence and non-existence. But even if vague existence is possible, here there is something weird. We have a continuum between something with the kinds of non-occurrent mental states that a person has—states like knowing how to speak German and believing that naturalism is true—and something without them. Moreover, if the epoxy cures uniformly, all of these states fizzle out uniformly. Now, maybe, we could imagine a person ceasing to exist gradually by having mental abilities go away one by one, losing memories one by one, and so on. But here at any time at which we have a person, we have a person with the same full set of the non-occurrent mental states of a person, adn then eventually we have something with no mental states at all. That seems weird.

If one thinks that the person continues to exist when the epoxy cures, but simply is encased in epoxy, then one is going to have to say that a plain block of marble with an energy source can also be a person, but one encased in marble (one can make gears out of marble): there really is a Hermes in the stone. And that's absurd.

Scenario 2: The epoxy has a slightly different chemical composition from the gears. After the person has ceased to exist due to the epoxy having set, a chemical removes the epoxy, leaving the gears intact. And so we have a person again. If temporal gaps in existence are possible, this case doesn't add anything to the story. But suppose temporal gaps are impossible. Then we have something weird. For we can make an argument that the person after the removal of the epoxy is the same as the person before. Here's the argument. We can imagine a variant story. In order to clean out and cool the system, during the rest state, water is poured into the gearbox and frozen. Then it's melted and removed. Intuitively, the person should count as surviving that. But how is that different from the epoxy case when the epoxy is going to be removed? It's not—so after the removal of the epoxy, we have the same person, which contradicts the assumption that temporal gaps are impossible.

Metaphysics argument contest: Persons and properties

I am holding a contest for the best argument against the thesis that some property is a person. There are a number of rules. The deadline is the end of February. See here for more contest information.

Aliens in the heavenly Jerusalem?

If Christianity is correct, there is at least a moderate probability that there are embodied intelligent persons other than humans. If so, will some of them be in the heavenly Jerusalem, too, available for us to interact with? I think that the value of unity between creatures gives a plausible affirmative argument. Over a finite amount of time, it might make sense that different intelligent species be sequestered, as inter-species communication has many difficulties. But given an infinite amount of time, it seems plausible that such contact would be appropriate. The heavenly choir, thus, may well include an intelligent gas cloud (not literally a gas cloud: a being of body and soul, whose body is composed of a gas cloud) slowly changing colors in a meaningful way, and chatting with St Thomas about divine simplicity.

Of course all such possibilities for wonder pale beside the simple wonder of union with God.

Why do we need bodies?

The following scenario is adapted from Keith Laumer's story "The Body Builders": Technology reaches the point that our brains, while still in our natural bodies, can be remotely connected to a synthetic body, which would be as manipulable and would provide as much and as good sensory input as our real bodies. The natural bodies, with brains in their skulls, can be kept in municipal storage, where they will be carefully maintained, exercised and kept trim and healthy, without us being aware of it, because the sensory connections between the brain and the rest of the natural body are severed. It seems the synthetic body could do all the tasks that the natural body could, but would provide two advantages: (a) it could technologically improve on the capabilities of the natural body, say, by providing more strength, agility or sensory data, and (b) one will avoid danger, since one's brain and natural body are safe in municipal storage while the synthetic body goes out into the world of whizzing cars, disease, and all that. Very quickly, one starts to feel about the synthetic body as if one were there, in it—as if it were one's own body.

Question: In a scenario like this, what would we lose? What couldn't we do in this scenario if we did everything through the synthetic body?

One class of activities that we would lose out on are various hobby and sport activities where the contingent limitations of our bodies are important. If various drugs are contrary to good sportsmanship (though, on the other hand, consider the case of Oscar Pistorius), obviously this will be. There can be sports that are played with synthetic bodies. They would in some way akin to remote control car racing. But they would, indisputably, be essentially different sports from the ones we have. (That's part of the point of the Laumer story.)

A second class of acitvities that we would lose out on are ones where physical danger appears to be central to meaning of the activity. Climbing Mt. Everest is a paradigm example. I am inclined to think activities where danger is courted are contrary to the virtue of prudence, since danger is a bad thing. If one could climb Mt. Everest while ensuring safety (e.g., by having a button which, if pressed, would teleport one to a medical facility), one should.

But both of the above classes of activities are pretty much optional to human life. We could get along pretty much fine without bodily sports or mountain climbing: we could still have video games, and cases where non-physical courage is exercised. We would lose out, but we would not lose out on all that much.

In thinking about this, the only cases of activities crucial to the good of humanity that I can think of which could not be done through the synthetic bodies would be:

1. Basic survival functions. (Those would need to be done in municipal storage.)
2. (a) Sexual union and (b) reproduction.
3. The sacraments of baptism, confirmation, Eucharist, ordination and annointing of the sick.

One might think (2a) could be done remotely, and (2b) could be done technologically in municipal storage (extracting sperm and egg, combining them, etc.) But this is mistaken. Sexual union is essentially embodied: the remote "union" would only illusorily be a physical union. And doing (2b) apart from (2a) is immoral—human beings should be the fruit of marital union.

It's interesting that apart from basic survival functions, all of the activities that are both crucial to the good of humanity and that require the natural body are sacraments or closely tied to sacraments ((2) is obviously closely tied to the sacrament of matrimony, as its consummation). It's also interesting that two sacraments are left off the list in (3): reconciliation and matrimony. While currently reconciliation is normally done through in-person confession, I do not think this is essential to the sacrament—I think the Church could change this (I am not saying it would be wise to change it) to confession, say, by telephone. (If general absolution is valid, remote absolution would probably be valid, too, if the Church allowed it.) And while matrimony essentially requires the exchange of consent, this consent need not be given in spoken words (Canon 1104.2), and it is permissible for the two parties to be present only by proxy (Canons 1104.1 and 1105). Still, the consummation must be happen in person for the marriage to be indissoluble.

That, apart from basic survival, all the most important non-survival functions for which a natural body is essential are religious ones or closely tied to religious ones neatly refutes the popular idea that the Christian Church thinks poorly of the human body.

A problem of the many

Assume compositional universalism, the doctrine that any bunch of non-overlapping objects have a whole which they wholly compose. Unger's problem of the many is that there seem to be too many people who think my thoughts. After all, if I think my thoughts, so does the guy composed of the same parts as I have, plus one additional particle near me, as does the guy composed of the same as I have, minus one flake of skin. There are solutions to this problem, however. For instance, it might be that for some reason only one of the composites is a person—maybe a person has to be maximal in some way, including all the parts. Or maybe persons are souls, or matter connected with a soul (and there is a metaphysical fact as to which particles are connected to a soul).

The only consistently unrestricted universalism that has any hope of truth, however, is what one might call modal universalism. I will give the four-dimensionalist version, but a three-dimensionalist version is just as easy. Modal universalism says that for any function f from worlds to sets of objects, such that all the f(w) are non-overlapping, and such that for at least one w the set f(w) is non-empty, there is an object O_f such that:

1. For all w, O_f exists at w if and only if f(w) is non-empty.
2. For all w, if f(w) is non-empty, then O_f is composed precisely of the members of f(w) at w.

(For the three-dimensionalist version, replace worlds with world-time pairs.) Bald claim: Anything more restrictive than modal universalism will either not yield all the objects of common sense, such as organisms and artefacts, or else will be ad hoc.

Modal universalism, however, gives a particularly serious problem of the many. Here is a rough-and-ready thesis:

3. Whether x is a person in the actual world thinking about p depends only on what x is up to at w and at worlds sufficiently close to the actual world.

To make this precise, one would need an account of categorical properties to spell out the "is up to".

Anyway, for any at all reasonable story about what "sufficiently close" means, according to modal universalism, there will be infinitely many entities that are composed of the same parts as I am in all the sufficient close worlds, but that differ in some odd way in the further worlds. (There is a being that has the same parts as me in all sufficiently close worlds, but in all further worlds is composed of number seven, assuming the number seven is an object.) By (3), they will be thinking about the same thing as I am. And hence we get too many thinkers thinking my thoughts. Moreover, to make things worse, if there are no empty worlds, some of these thinkers will be necessary beings (e.g., the Pruss/Number-7 being of my previous paranthetical remark).

Now something like a maximality condition, or bringing in souls, may help with Unger's original problem. But there would still be this version to tackle.

Maybe introducing some story about naturalness will help. Maybe only the more natural entities think, and an entity that is composed of the same parts as I at all close worlds and of the number seven at all other worlds isn't natural. However, at some distant worlds, there will be multiple, equally natural (at least if natural is linked with simplicity of law and that sort of thing), choices for f(w), even if we constrain that f(w) = { me } at all close worlds. Unless, of course, naturalness is some kind of metaphysical primitive, having nothing much to do with simplicity of law and so on. So that's a way out, but I doubt it will appeal to many modal universalists.

Let me end with a note about a different topic. I suspect that the only ontology that will support a psychological theory of personal identity will be a universalist one. Thus, this might yield an argument against psychological theories of personal identity.

[Minor errors fixed.]

Deep Thoughts XII

Everyone is an individual.

Livers, brains, conscious computation and teleology

Let us suppose, for the sake of exploration the following (false) thesis:

1. I am conscious because of a part of me—viz., my brain—engaging in certain computations which could also be engaged in by sophisticated computers, thereby rendering these computers conscious.

I will also assume the following, which seems obvious to me, but I think in the end we will find that there is a tension between it and (1):

2. The brain and liver are both proper parts of me.

Call the kinds of computations that give rise to consciousness "C-computations". So by (1) I am conscious because of my brain's C-computations, and if my laptop were to engage in C-computations, that would give rise to consciousness in it.[note 1]

Now, let us imagine that my liver started doing C-computations within itself, but did not let anything outside it know about this. Normally, livers regulate various biochemical reactions unconsciously (I assume), but let us imagine that my liver became aware of what it was doing through engaging in C-computations on the data available to it. Of course, livers can't willy nilly do that. So, part of my supposition is that the structure of my liver, by a freak of nature or nurture, has shifted in such wise that it became a biochemical computer running C-computations. As long as the liver continued serving my body, with the same external functions, this added sophistication would not (I assume) make it cease to be a part of me.

So now I have two body parts where C-computations go on: my brain and my liver. However, the following is very plausible to me:

3. Whatever computations my liver were to perform, I would do not have direct awareness of what is going in my liver, except insofar as the liver transmitted information to its outside.

In the hypothesis I am considering, the liver "keeps to itself", not sending data into my nervous system about its new computational activities. So, I submit, I would not be aware of what is going on there. Thus, there would be consciousness, since there would be C-computations, but it would not be consciousness that I have.

But now we have a puzzle. In this setup, I am conscious in virtue of the neural computations that my brain engages in, but am not conscious in virtue of the hepatic computations that my liver engages in. Thus, when my neural computation is quiescent due to sleep, but my hepatic computation continue, I am, simpliciter, not conscious. Why? After all, both the brain and the liver are parts of me. The brain also "keeps to itself": it only lets the rest of the body have the outputs of its computation, but the details of it, it keeps to itself, just as in my thought experiment the liver does. The idea in (1) seemed to have been that computational activity by an organic part of me would give rise to consciousness that is mine. But by the same token the hepatic computational activity should give rise to consciousness that is mine.

So what should someone who accepts (1), (2) and (3) (and the various subsidiary assumptions) say about this? Well, I think the best thing to do would be to abandon (1), denying that I think in virtue of computational activity. A second-best solution would be to qualify (2): yes, the brain and the liver are parts of me, but the brain is a more "intimate" or "central" part of me. But note that one cannot explain this intimacy or centrality in terms of the brain's engaging in computational activity. For the liver could do that, too. Could one explain it in terms of how much coordinating the brain actually does of my bodily functions, both voluntary and not? Maybe, but this has to be taken teleologically. For we can imagine as part of the thought experiment that I become paralyzed, and my brain no longer coordinates my bodily functions, but they are in fact coordinated by medical technology. So the defender of (1) who wishes to qualify (2) in this way may have to embrace teleology to account for the difference between the brain and the liver.

But there may be another solution that doesn't seem to involve teleology. One might say that each bundle of C-computational activities gives rise to a conscious being. Thus, perhaps, in my thought experiment, there are two persons, who contingently have all of their parts in common: (a) the neural person that I am, and (b) the hepatic person that I am not. Contingently, because if the liver were replaced by a prosthesis that maintains basic bodily functions, (b) would die, but (a) would continue to exist, while if the brain were replaced by such a prosthesis, (a) would die, but (b) would continue to exist. This view can be seen as a way of qualifying (2): yes, both the brain and the liver are parts of me, but one is an essential part and the other not. On this view, the claim is that:

4. I am conscious in virtue of C-computations in an essential part of me.

But actually further qualification is needed. For suppose that instead of my liver becoming conscious, one of my neurons were to suddenly complexify immensely, while retaining the same external functions, so that internally it was engaging in sophisticated C-computations, while externally it worked like every other neuron. It seems that an analogue to (3) would still hold—I wouldn't be aware of what the neuron is aware of (but I admit that my intuition is weaker here). And so (4) is false—for the C-computations in the neuron are computations in the brain, and the brain is an essential part of me, but I am not conscious in virtue of them.

It is difficult to fix up (4). One might require that the computations take place throughout the whole of the essential part. But supposing that for a while my left brain hemisphere fell asleep while the right continued C-computing (dolphins practice such "unihemispheric sleep"), then the computations would not be taking place throughout the whole of the essential part. But I would, surely, still be aware. I am not sure there is any way of fixing up (4) to avoid the conscious-neuron and unihemispheric sleep counterexamples. If not, and if no other two-persons-in-one-body solution can be articulated, then the teleological solution may be needed.

Final remarks: I think naturalism requires something like (1). If so, then given the plausibility of (2) and (3), naturalists need to accept teleology. But teleology does not fit well into naturalism. So naturalism is in trouble.

Progress report: naturalism and persons

This is just a progress report, a promissory note without much argument. I've been thinking a lot about naturalism and persons. Specifically, I've been thinking whether there is room for persons in a naturalistic ontology. One lemma that I've become convinced of is that if necessarily all persons are substances, so that if x is a person, then for x to exist is not a matter of something beyond x having some property or standing in some relation, then naturalism is false. In an earlier post, I gave an argument for this conclusion based on speculative physics, but now I am convinced that the conclusion holds independently of the speculative physics. Basically, the idea is that if naturalism holds, strong AI is true (it would be too weird if naturalism were true but minds had to be tied to a biology like ours), but if strong AI is true, then I suspect it is possible for a token computer program to be a person, and token computer programs are not substances (their existence is a matter of a computer having a particular state).

Moreover, it is plausible that finite persons are ontologically homogeneous: if one finite person is a substance, they all necessarily are. If this is correct, then if we are substances, naturalism is false.

Are persons substances? Are we substances? If we adopt an Aristotelian ontology, there are three alternatives to a person being a substance: she might be accident-like (e.g., a trope or a token relation), she might be the essence of a substance, or she might not exist. I take it that persons exist. The same kinds of thoughts that suggest that if naturalism holds, persons need not be substances, also suggest that if naturalism holds, then persons need not be essences of substances. So, on this kind of ontology, the question comes down to: Can persons be accident-like?

But consider the following thoughts: (a) if naturalism is true, then the best theory of personal identity will be a memory-based theory, (b) programs can seamlessly move between processors and even between computers, and (c) accident-like entities cannot move between substances. To me, these thoughts suggest that if naturalism holds, persons can't be accident-like, unless appearances are deceiving and moving from one body to another, or one computer to another, wouldn't involve a movement between substances. But the only way this could be is if the persons are accidents of some grand global substances, like the Cosmos, or Spacetime, or the Fields of a unified field theory.

Thus, assuming an ontology that has only substances and accident-like entities, the conclusion I draw is that if naturalism holds of persons, we are all modes (to use Spinozostic terminology) of one or more global substances. I doubt that on a sparse theory of properties and relations there will be enough modes to do the job. So the ontology will have to be one on which there are one or more global substances, of which everything else is a mode, and the modes are abundant. Moreover, since we have properties, this ontology will have to be one on which accident-like entities can be nested. I suspect that abundance will cause Unger-like problems with identifying who exactly we are, but I would like to have a better argument against such a Spinozistic ontology.

So this is where I am at right now in the argument: either some non-naturalistic account of persons is true, or a Spinozistic naturalistic ontology of one or more global substances, with nestable modes, probably abundant, holds. Of course I am convinced that the Spinozistic account is false (if only for ethical reasons: it doesn't do justice to the ethical importance of the body), but it would be nice to have a good ontological arguemnt here. With some modal imagination we might make progress: for instance we might think that even if in fact such an ontology holds, surely it would be possible to have persons apart from such an ontology, and this is enough to sink the naturalistic account. But I would rather not rely on modal imagination.

There is a lot of detail here that can be questioned. But the basic idea is, I think, sound: further progress on the question of whether the existence of persons is compatible with naturalism is going to be a matter not just of metaphysica specialis but of metaphysica generalis (i.e., of ontology).