Immortality of the soul and the soul's proper operation

This is an attempt to make an argument for the natural immortality of the soul from the premise that the soul has a proper operation that is independent of the body. The argument is going to be rather odd, because it depends on my rather eccentric four-dimensionalist version of Aristotelian metaphysics.

Start with the thought of how substances typically grow in space. They do this by causing themselves to have accidents in new locations, and they come to exist where these new accidents are. Thus, if I eat and my stomach becomes distended, I now have an accident of stomachness in a location where previously I didn’t, and normally I come to be partly located where my accidents are.

It is plausible (at least to a four-dimensionalist) that spatiotemporal substances grow in time like they grow in space. Thus, they produce accidents in a new temporal location, a future one, and typically come to be located where the accidents are—maybe they come to be there by being active in and through the accidents. (There are exceptions: in transsubstantiation, the bread and wine don’t follow their accidents. But I am focusing on what naturally happens, not on miracles.)

Suppose now that the soul has a proper operation that is independent of the body. Given the fact that my intellectual function is temporal in nature, it is plausible that in this proper operation, my soul is producing a future accident of mine—say, a future accident of grasping some abstract fact—and does so regardless of how sorry and near-to-death a state my body has. But a substance normally stretches both spatially and temporally to become partly located where its accidents are. So by producing a future accident of mine the soul normally ensures that I will be there in that future to be active in and through that accident. Thus the soul, in exercising that future-directed proper activity, makes me exist in the future.

Now that I’ve written this down, I see a gap. The fact that the soul has a proper operation independent of the body does not imply that the soul always engages in that operation. If it does not always engage in that operation, then there is the danger that if my body should perish at a time when the operation is not engaged in, the soul would fail to extend my existence futureward, and I would perish entirely.

On this version of the proper function argument, we thus need a proper operation that the soul normally or naturally always engages in. We might worry, however, that the intellectual operations all cease when we are in dreamless sleep. However, we might suppose that the soul by its nature always carries forward in time some aspect of the understandings or abstractions that it has gained, and this carrying forward in time is indeed a proper operation that occurs even in dreamless sleep, since we do not lose our intellectual gains when we are asleep. (We should distinguish this carrying forward of an aspect of the intellectual gains from the aspects of memory that are mediated by the brain. The need to do this is a weakness of the argument.)

The above depends on my idiosyncratic picture of persistence over time: substances cause their future existence. Divine sustenance is divine cooperation with this causation. The argument has holes. But I feel I may be on to something.

The argument does not establish that we necessarily are immortal. We are only naturally immortal, in that normally we do not perish. It is possible, as far as the argument goes, that the proper operation should fail to succeed in extending us into the future, if only because God might choose to stop cooperating in the way that constitutes sustenance (but I trust he won’t).

Aquinas' argument for the immortality of the soul

Aquinas argues that because the human soul has a proper operation—abstract thought—that does not depend on the body, the soul would survive the destruction of the body.

I’ve never quite understood this argument. It seems to show that there could be a point to the soul surviving the destruction of the body, but that doesn’t show that it will.

It seems that by the same token one could say that because my fingers have an operation independent of my toes, my fingers would survive the destruction of the toes. But that need not be true. I could simultaneously have my toes and fingers crushed, and the fingers’ having an operation independent of the toes would do nothing to save them. In fact, in most cases, fingers perish at the same time as toes do. For in most, though not all, human lives, fingers perish when a person dies, and the toes do so as well. So the argument can’t be that strong.

Still, on reflection, there may be something we can learn from the fingers and toes analogy. We shouldn’t expect the fingers to perish simply as a metaphysical consequence of my toes perishing. By analogy, then, we shouldn’t expect the soul to perish simply as a metaphysical consequence of the body perishing. That’s not the immortality of the soul, but it’s some progress in that direction. After all, the main reason for thinking the soul to perish at death is precisely because one thinks this is a metaphysical consequence of the body perishing.

And I am not denying that there are good arguments for the immortality of the human soul. I think there may be an argument from proper operation that makes even more progress towards immortality, but I’ll leave that for another occasion. Moreover, I think the immortality of the human soul follows from the existence of God and the structure of human flourishing.

The fundamentality of souls

Some dualists say that the soul is a fundamental entity.

I think we’re not in a position to think that. Compare this. We have no reason to think electrons are not elementary particles. They certainly aren’t made of any of the other particles we know of, so they are, we might say, “relatively elementary” with respect to the particles we know. But we would not be very surprised if electrons turned out to be made of other particles.

Similarly, we have good reason to think the soul is not grounded in any of the other things we know of (matter, accidents, etc.) But we should not be really surprised if a finer-grained analysis would reveal the soul to have a grounding structure beyond our current knowledge. We should be cautious and say the soul is “relatively fundamental” with respect to the entities we know.

God's vision of reality

Consider the simple theory of visual sensation on which for me to have a visual sensation as of y is for x to stand in a “vision relation” to y, with the relation being external to x so that x is no different intrinsically when x has a visual sensation as of a red cube and when x does not.

We know that this simple theory is false of us for the obvious reason that we suffer from visual hallucinations or illusions: there are cases where we have a visual sensation as of a red cube in the absence of a red cube. Our best explanation of visual misperception is that visual sensation is mediated by an internal state of ours that can occur in the absence of the apparently visually sensed object. Thus, we have internal modifications—accidents—of visual perception.

But now consider what I think of as the biggest objection to the doctrine of divine simplicity: God’s knowledge of contingent facts. This objection holds that God must be internally different in worlds where what he knows is different, or at least sufficiently different. This objection is based on the intuition that knowledge is written into the knower, that it is an intrinsic qualification of the knower.

Let’s, however, think what a perfect knower’s knowledge would be like. My knowledge divides into the dispositional and the occurrent: I dispositionally know my multiplication table, but at most one fact from that table is occurrent at any given time. It is clear that having merely dispositional knowledge is not the perfection of knowledge. A perfect knower would know all reality occurrently at once. Moreover, my knowledge varies in vividness. Some things, like perhaps the fundamental theorem of algebra, I know “theoretically” (in the modern sense of the word, not the etymological one) and “discursively”, and some facts—such as my visual knowledge of the screen in front of me—are vividly present to my mind. The vivid knowledge is more perfect, so we would expect a perfect knower to know all reality occurrently at once in the liveliest and most vivid way, more like in a vision of reality than in a discursive mental representation.

Let’s go back to the simple theory of visual sensation. Our reason for rejecting that theory in our own case was that it did not accord with the fact that humans are subject to visual misperception. But suppose that we never misperceived. Then we could easily believe the simple theory, at least until we learned a bit more about the contingent causal processes behind our visual processing.

Thus, the reason for rejecting the simple theory in our case was our imperfection. But this leaves open the possibility that something like the simple theory could hold for the vision-like knowledge of reality that a perfect knower would have. Such a knower might not have any internal state “mirroring” reality, but might simply have reality related to it in a relation of being-known which is external on the knower’s side. In the case of a perfect knower, we have no need to account for a possibility of misperception. Thus, the perfect knower may know me simply by having me be related to it by a relation of being-known, a relation external to the knower.

Objection 1: How do we account for God’s knowledge of absences, such as his knowledge that there are no unicorns? This cannot be accounted for by a relation between God and the absence of unicorns, since there is no such thing as the absence of unicorns.

Response: In the case of an imperfect knower, absence of knowledge is not knowledge of absence, since there is always the possibility of mere ignorance. But perhaps in the case of a perfect knower, knowledge of absence is constituted by absence of knowledge.

Objection 2: This account makes the perfect knower’s “knowledge” too different from ours for us to use the same word “knowledge” for both.

Response 1: We have good reason to think that all words applied to us and the perfect being to be applied merely analogously. A perfect being would be radically different from us.

Response 2: While the simple theory is false of us, given dualism we may have a somewhat more complex theory that is not so different from what I said about God. We have significant empirical reason to think that the brain is modified by our visual experiences, and that our visual experience is in some way determined by an internal state of the brain. However, if we are dualists, we will not think that the internal state of the brain is sufficient to produce a visual experience. There could be zombies with brains in the same state that we are in when we are seeing a red cube, but who do not see.

We can now give two different dualist theories about how I come to see a red cube. Both theories suppose an internal red-cube-mirroring state r_b of my brain. On the causal theory, the state r_b then causes an internal state r_s of the soul (=mind) which mirrors the relevant features of r_b, and I have a red-cube experience precisely in virtue of my soul hosting r_s. But the causal theory is not the only option for the dualist. There is also a relational theory, on which my red-cube experience is constituted by my soul’s standing in an external relation to the brain state r_b.

The two theories yield different predictions as to possibilities. On the causal theory, it is possible for me to have a red-cube experience in a world where God and my soul (and my soul’s states and me-constituted-by-my-soul) are all that exists—all that’s needed is for God to miraculously cause r_s in my soul in the absence of r_b. On the relational theory, on the other hand, I can only have a red-cube experience when my soul stands in a certain external relation to a brain state, and in that God-and-my-soul world, there are no brain states.

The causal theory of our visual perception is indeed very different from the external-relation theory of divine knowledge. The relational theory, however, is more analogous. The main difference is that our visual experiences come not from our mind’s direct relation to the external world, but from our mind’s (=soul’s) direct relation to a representing brain state. And that is very much a difference we would expect given our imperfection and God’s perfection: we would expect a perfect knower’s knowledge to be unmediated.

We have reason independent of divine simplicity not to opt for the causal theory in the case of God. First, on the causal theory, we seem to have great power over God: every movement of ours causes an effect in God. That seems to violate divine aseity. Second, the causal theory in the case of God seems to lead to a nasty infinite causal chain: if God’s vision-like knowledge of y is caused by y, then we would expect that God’s knowledge of his knowledge of y is caused by his knowledge of y, which leads to an infinite causal chain. Moreover, God would know every item in this infinite sequence, which leads to a second causal chain (God’s knowledge of God’s knowledge of … the first chain). This would violate causal finitism, besides seeming simply wrong.

Do we have independent reason to opt for the causal over the relational theory in our case, or perhaps the other way around? I don’t know. Until today, I assumed the causal theory to be correct. But the relational theory makes for a more intimate connection between the soul and brain, and this is somehow appealing.

Ill-suited matter, form, and immortality

A question I haven’t seen explored much by contemporary neo-Aristotelian metaphysics is that of matter ill-suited to the form. Is it metaphysically possible for a bunch of molecules arranged like a normal oak tree to have the form of a pig? It would be, of course, a very unfortunate pig. Or is some minimal amount of match between the actual arrangement of the molecules and the form needed?

On light-weight neo-Aristotelianism, on which forms are simply structural properties, the answer has got to be negative.

But on heavy-weight neo-Aristotelianism, on which forms are irreducible entities, it seems like there should be no such restrictions. Why couldn’t God unite the form of a pig with a body as of an oak tree, or the form of an oak tree with a body as of a human?

However, supposing that we take such a liberal view on which there is no such thing as matter metaphysically incompatible with a form (presumably pace historical Aristotelians), we then have a puzzle. If it would be metaphysically possible for a pig form to be united to a bunch of organic gases, why is it that when pigs are vaporized, they (we assume) invariably die? Here is my story. Assume for simplicity time is discrete. At each time t, a pig—in virtue of its form—has a causal power to continue existing at the next time. But causal powers have activation conditions. The activation condition for the causal power to continue existing at the next time is an appropriate arrangement of the pig’s body. When the pig’s body becomes so distorted that this activation condition is no longer satisfies, the pig loses the power to go on living. And so it dies. However, of course, God could make it keep on living by a miracle: a miracle can supply what the causal powers of a thing are incapable of.

This account has one somewhat implausible prediction. Suppose that some powerful being instantaneously scatters the molecules of an ordinary pig across the galaxy, so that at t₁ we have an ordinary pig and at the next time, t₂, the pig molecules are scattered. Because at t₁ the pig has a causal power of continuing to exist conditionally on its molecules being appropriately arranged at t₁, and this condition is indeed satisfies at t₁, the pig will live one moment in scattered condition at t₂—and then perish at the next moment, t₃.

On this account, external causes do not directly destroy an object. Rather, they destroy the activation condition for the object’s power to continue existing. When that activation condition is destroyed, the object (barring a miracle) ceases to exist. But it has that one last existential hurrah before it falls into nonbeing.

Does it follow that on a heavy-weight Aristotelianism with my story about death, a pig metaphysically could survive the annihilation of its body? I am not sure, but I am inclined to think so. Indeed, I am inclined to think that if we had a normal pig at t₁, and then at t₂ the matter of the pig were annihilated, the pig would still exist—reduced to an abnormal immateriality—for that one instant of t₂, and then, barring a second miracle, it would slide into non-being at t₃.

What about us? Well, Aquinas argues for our soul’s natural immortality on the grounds that the human soul has a proper operation that does not depend on the matter, namely pure thought. I have never before been impressed by the move from a proper operation independent of matter to natural immortality, but in my above (neo-Aristotelian but not very Thomistic) setting I see it having significant force. First, we have this question: What are the activation conditions for the human’s power-to-continue-existing? It makes sense that for a being whose only non-existential operations are material, the activation conditions should be purely material. But if a being has a proper operation not dependent on the matter, then it makes perfect sense for the activation conditions of its power-to-continue-existing not to include material conditions. In fact, something stronger can be said. It seems absurd for a thing to have a power to continue thinking whose activation conditions outstrip its power to continue existing. It would be like a power to play soccer without a power to move. So, it seems, if Aquinas is right that we have an immaterial operation, then we have the power to continue existing even absent a body. Of course, God can stop cooperating with any power we have, and if he stopped cooperating with our power-to-continue-existing, then we would stop existing (unless God miraculously sustained us in existence independently of that power!), but naturally we would continue to exist. Assuming, of course, Thomas is right about us having a proper operation that does not depend on matter, which is a different question.

(And unlike Thomas, I think we have immortality, not just our souls.)

Aquinas and Descartes on substance dualism

Roughly, Aquinas thinks of a substance as something that:

1. is existentially independent of other things, and

2. is complete in its nature.

There is a fair amount of work needed to spell out the details of 1 and 2, and that goes beyond my exegetical capacities. But my interest is in structural points. Things that satisfy (1), Aquinas calls “subsistent beings”. Thus, all substances are subsistent beings, but the converse is not true, because Aquinas thinks the rational soul is a subsistent being and not a substance.

Descartes, on the other hand, understands substance solely in terms of (1).

Now, historically, it seems to be Descartes and not Thomas who set the agenda for discussions of the view called “substance dualism”. Thus, it seems more accurate to think of substance dualists as holding to a duality of substance in Descartes’ sense of substance than in Aquinas’.

But if we translate this to Thomistic vocabulary, then it seems we get:

3. A “substance dualist” in the modern sense of the term is someone who thinks there are two subsistent beings in the human being.

And now it looks like Aquinas himself is a substance dualist in this sense. For Aquinas thinks that there are two subsistent beings in Socrates: one of them is Socrates (who is a substance in the Thomistic sense of the word) and the other is Socrates’ soul (which is a merely subsistent being). To make it sound even more like substance dualism, note that Thomas thinks that Socrates is an animal and animals are bodies (as I have learned from Christopher Tomaszewski, there are two senses of body: one is for the material substance as a whole and the other is for the matter; it is body in the sense of the material substance that Socrates is, not body in the sense of matter). Thus, one of these subsistent beings or substances-in-the-Cartesian-sense is a body and the other is a soul, just as on standard Cartesian substance dualism.

But of course there are glaring difference between Aquinas’ dualism and typical modern substance dualisms. First, and most glaringly, one of the two subsistent beings or Cartesian substances on Aquinas’s view is a part of the other: the soul is a part of the human substance. On all the modern substance dualisms I know of, neither substance is a part of the other. Second, of the two subsistent beings or Cartesian substances, it is the body (i.e., the material substance) that Aquinas identifies Socrates with. Aquinas is explicit that we are not souls. Third, for Aquinas the body depends for its existence on the soul—when the soul departs from the body, the body (as body, though perhaps not as matter) perishes (while on the other hand, the soul depends on the matter for its identity).

Now, let’s move to Descartes. Descartes’ substance dualism is widely criticized by Thomists. But when Thomists criticize Descartes for holding to a duality of substances, there is a danger that they are understanding substance in the Thomistic sense. For, as we saw, if we understand substance in the Cartesian sense, then Aquinas himself believes in a duality of substances (but with important structural differences). Does Descartes think there is a duality of substances in the Thomistic sense? That is not clear to me, and may depend on fine details of exactly how the completeness in nature (condition (2) above) is understood. It seems at least in principle open to Descartes to think that the soul is incomplete in its nature without the body or that the body is incomplete in its nature without the soul (the pineal gland absent the soul sure sounds incomplete) or that each is incomplete without the other.

So, here is where we are at this point: When discussing Aquinas, Descartes and substance dualism we need to be very careful whether we understand substance in the Thomistic or the Cartesian sense. If we take the Cartesian sense, both thinkers are substance dualists. If we take the Thomistic sense, Aquinas clearly is not, but it is also not clear that Descartes is. There are really important and obvious structural differences between Thomas and Descartes here, but they should not be seen as differences in the number of substances.

And here is a final exegetical remark about Aquinas. Aquinas’ account of the human soul seems carefully engineered to make the soul be the sort of thing—namely, a subsistent being—that can non-miraculously survive in the absence of the substance—the human being—that it is normally a part of. This makes it exegetically probable that Aquinas believed that the soul does in fact survive in the absence of the human being after death. And thus we have some indirect evidence that, in contemporary terminology, Aquinas is a corruptionist: that he thinks we do not survive death though our souls do (but we come back into existence at the resurrection). For if he weren’t a corruptionist, his ontology of the soul would be needlessly complex, since the soul would not need to survive without a human being if the human being survived death.

And indeed, I think Aquinas’s ontology is needlessly complex. It is simpler to have the soul not be a subsistent being. This makes the soul incapable of surviving death in the absence of the human being. And that makes for a better view of the afterlife—the human being survives the loss of the matter, and the soul survives but only as part of the human being.

A metaphysical argument for survivalism

Corruptionist Thomists think that after death and before the resurrection, our souls exist in a disembodied state and have mental states, but we do not exist. For we are not our souls. Survivalist Thomists think we continue to exist between death and the resurrection. They agree that we are not our souls, but tend to think that in the disembodied we have our souls as proper parts.

Here is a metaphysical argument against corruptionism and for survivalism.

1. An accident that has a subject is a part of that subject.

2. There are mental state accidents in the disembodied state.

3. All mental state accidents in the disembodied state have a subject.

4. The soul does not have accidents as parts.

5. Therefore, the mental state accidents in the disembodied state have something other than the soul as their subject.

6. The only two candidates for a subject of mental state accidents are the soul and the person.

7. Therefore, the mental state accidents in the disembodied state have the person as their subject.

8. Therefore, the person exists in the disembodied state.

(This argument is a way of turning Jeremy Skrzypek’s accident-based defense of survivalism into a positive argument for survivalism. Maybe Skrzypek has already done this, too.)

The argument is slightly complicated by the fact that Thomists accept the possibility of subjectless accidents existing miraculously (in the Eucharist). Nonetheless, I do not know of any Thomists who think the disembodied state is such a miracle. Given that Thomists generally think that the survival of the soul after death is not itself miraculous, they are unlikely to require the miracle of subjectless accidents in that case, and hence will accept premise 3.

Premise 2 is common ground between survivalists and corruptionists, as both agree that there is suffering in hell and purgatory and joy in heaven even in the disembodied state.

I think the controversial premises are 1 and 4. I myself am inclined to deny the conjunction of the two premises (even though I think survivalism is true for other reasons).

Premise 1 is a core assumption of compositional metaphysics, and compositional metaphysics is one of the main attractions of Thomism.

One reason to accept premise 4 is that the soul is the form of the human being, and one of the main tasks for forms in Aristotelian metaphysics is to unify complex objects. But if forms are themselves complex, then they are also in need of unification, and we are off on a regress. So forms should be simple, and in particular should not have accidents as parts.

Another reason to accept 4 is that if the soul or form has mental state accidents as parts, it becomes very mysterious what else the form is made of besides these accidents. Perhaps there is the esse or act of being. But it seems wrong to think of the form as made of accidents and esse. (I myself reject the idea that objects are “made of” their parts. But the intuition is a common one.)

Two interaction problems

Yesterday I realized something that should have been obvious: there are two separate interaction problems for dualism.

1. Metaphysics: How does the soul manage to cause effects in the body?

2. Physics: Wouldn’t such causation violate the laws of physics?

I used to think of the interaction problem as just (1), and hence I thought it was spurious once one learned from Hume that all cases of causation are equally mysterious.

But problems (1) and (2) are pretty independent: one can have a solution to each without a solution to the other. For instance, an indeterministic physics provides a solution to (2), but says nothing about (1), while occasionalism and hylomorphism provide solutions to (1), but say little about (2).

While I think the questions are interesting, I don’t really think either poses a serious problem for interactionist dualism.

Disembodied trees

Here’s an interesting thesis:

1. If x has the ys among its parts, and for each z among the ys, x can survive losing z without gaining anything, then x can survive simultaneously losing all the ys without gaining anything.

There are obvious apparent counterexamples. A boat that has sufficient redundancy can survive the loss of any plank, but cannot survive losing them all. An oak tree can lose any cell but cannot lose all cells.

But counterexamples aside, wouldn’t (1) be a nice metaphysical thesis to have? Then essential parts wouldn’t be made of inessential ones. You can see all the nasty ship-of-Theseus questions that would disappear if we had (1).

I think an Aristotelian can embrace (1), and can get around the counterexamples by biting some big bullets. First, like some contemporary Aristotelians, she can deny that artifacts like boats (or bullets) exist. Second, she can say that oak trees can survive the loss of all their matter, becoming constituted by form alone, much as some philosophers say happens to human beings after death (before the resurrection). The second part seems a bigger bullet to bite, as one would need a story as to why in fact oak trees perish when they lose all their cells, even if they don’t have to. But perhaps that’s just contingently how it happens, though an all powerful being could make an oak tree survive the destruction of all its cells.

The big question here is exactly what philosophical advantages embracing (1) has.

Self-consciousness and AI

Some people think that self-consciousness is a big deal, that it’s the sort of thing that might be hard for an artificial intelligence system to achieve.

I think consciousness and intentionality are a big deal, that they are the sort of thing that would be hard or impossible for an artificial intelligence system to achieve. But I wonder whether if we could have consciousness and intentionality in an artificial intelligence system, would self-consciousness be much of an additional difficulty. Argument:

1. If a computer can have consciousness and intentionality, a computer can have a conscious awareness whose object would be aptly expressible by it with the phrase “that the temperature here is 300K”.

2. If a computer can have a conscious awareness whose object would be aptly expressible by it with the phrase “that the temperature here is 300K”, then it can have a conscious awareness whose object would be aptly expressible by it with the phrase “that the temperature of me is 300K”.

3. Necessarily, anything that can have a conscious awareness whose object would be aptly expressible with the phrase “that the temperature of me is 300K” is self-conscious.

4. So, if a computer can have consciousness and intentionality, a computer can have self-consciousness.

Premise 1 is very plausible: after all, the most plausible story about what a conscious computer would be aware of is immediate environmental data through its sensors. Premise 2 is, I think, also plausible for two reasons. First, it’s hard to see why awareness whose object is expressible in terms of “here” would be harder than awareness whose object is expressible in terms of “I”. That’s a bit weak. But, second, it is plausible that the relevant sense of “here” reduces to “I”: “the place I am”. And if I have the awareness that the temperature in the place I am is 300K, barring some specific blockage, I have the cognitive skills to be aware that my temperature is 300K (though I may need a different kind of temperature sensor).

Premise 3 is, I think, the rub. My acceptance of premise 3 may simply be due to my puzzlement as to what self-consciousness is beyond an awareness of oneself as having certain properties. Here’s a possibility, though. Maybe self-consciousness is awareness of one’s soul. And we can now argue:

5. A computer can only have a conscious awareness of what physical sensors deliver.

6. Even if a computer has a soul, no physical sensor delivers awareness of any soul.

7. So, no computer can have a conscious awareness of its soul.

But I think (5) may be false. Conscious entities are sometimes aware of things by means of sensations of mere correlates of the thing they sense. For instance, a conscious computer can be aware of the time by means of a sensation of a mere correlate—data from its inner clock.

Perhaps, though, self-consciousness is not so much awareness of one’s soul, as a grasp of the correct metaphysics of the self, a knowledge that one has a soul, etc. If so, then materialists don’t have self-consciousness, which is absurd.

All in all, I don’t see self-consciousness as much of an additional problem for strong artificial intelligence. But of course I do think that consciousness and intentionality are big problems.

Dualist survivalism

According to dualist survivalism, at death our bodies perish but we continue to exist with nothing but a soul (until, Christians believe, the resurrection of the dead, when we regain our bodies).

A lot of the arguments against dualist survivalism focus on how we could exist as mere souls. First, such existence seems to violate weak supplementation: my souls is proper part of me, but if the body perished, my soul would be my only part—and yet it would still be a proper part (since identity is necessary). Second, it seems to be an essential property of animals that they are embodied, an essential property of humans that they are animals, and an essential property of us that we are humans.

There are answers to these kinds of worries in the literature, but I want to note that things become much simpler for the dualist survivalist if she accepts a four-dimensionalism that says that we are four-dimensional beings (this won't be endurantist, but it might not be perdurantist either).

First, there will be a time t after my death (and before the resurrection) such that the only proper part of mine that is located at t is my soul. However, the soul won’t be my only part. My arms, legs and brain are eternally my parts. It’s just that they aren’t located at t, as the only proper part of me that is located at t is my soul. There is no violation of weak supplementation. (We still get a violation of weak supplementation for the derived relation of parthood-at-t, where x is a part-at-t of y provided that x is a part of y and both x and y exist at t. But why think there is weak supplementation for parthood-at-t? We certainly wouldn’t expect weak supplementation to hold for parthood-at-z, where z is a spatial location and x is a part-at-z of y provided that x is a part of y and both x and y are located at z.)

Second, it need not follow from its being an essential property of animals that they are embodied that they have bodies at every time at which they exist. Compare: It may be an essential property of a cell that it is nucleated. But the cell is bigger spatially than the nucleus, so it had better not follow that the nucleus exists at every spatial location at which the cell does. So why think that the body needs to exist at every temporal location at which the animal does? Why can’t the animal be bigger temporally than its body?

Of course, those given to three-dimensional thinking will say that I am missing crucial differences between space and time.

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.

Introducing doppelgangers

Yesterday, I mentioned that one might reinterpret the quantifier symbols in a language so as to introduce doppelgangers: extra quasi-entities that just don't exist, but get to be talked about using standard quantifier inference rules. Here I want to give a bit more detail, and then offer a curious application to the philosophy of mind: an account of how a materialist could use a doppelganged reinterpretation of language to talk like a hard-core dualist. The application shows that it is philosophically crucial that we have a way to distinguish between real quantifiers and mere quasi-quantifiers (in the terminology of the previous post) if we want to distinguish between materialism and dualism.

Onward! Let L be a first-order language with identity. A model M for L will be a pair (D,P), where D is a non-empty set ("domain") and P is a set of subsets ("properties") of D. A doppel-interpretation of L is a pair (I,s) where I is a function from the names and predicates other than identity to D and P respectively and s is a function from names to the set {0,1} ("signature"). The signature function s tells us which name is attached to an ordinary object (0) and which to a doppelganger (1).

Now a substitution vector for a doppel-interpretation (I,s) will be a partial function v from the names and variables of L to D such that v(a)=I(a) whenever a is a name. A signature vector is a partial function f from the names and variables of L to D such that f(a)=s(a) whenever a is a name. If x is a variable and u is in D, then I will write v(x/u) for the substitution vector that agrees with v except that v(x/u)(x)=u. I.e., v(x/u) takes v and adds or changes the substitution of u for x. Likewise, if f is a signature vector, then s(x/n) agrees with s except that s(x/n)(x)=n for n in {0,1}.

We can now define the notion of a substitution and signature vector pair (v,f) doppel-satisfying a formula F in L under a doppel-interpretation (I,s). We begin with the normal Tarskian inductive stuff for truth-functional connectives:

• (v,f) doppel-satisfies F or G iff (v,f) doppel-satisfies F or (v,f) doppel-satisfies G
• (v,f) doppel-satisfies F and G iff (v,f) doppel-satisfies F and (v,f) doppel-satisfies G
• (v,f) doppel-satisfies ~F iff (v,f) doesn't doppel-satisfies F.

Now we need our quasi-quantifiers:

• (v,f) doppel-satisfies ∃xF iff for some u in D, (v(x/u),f(x/0)) doppel-satisfies F or for some u in D, (v(x/u),f(x/1)) doppel-satisfies F
• (v,f) doppel-satisfies ∀xF iff for every u in D, (v(x/u),f(x/0)) doppel-satisfies F and for every u in D, (v(x/u),f(x/1)) doppel-satisfies F.

Then we need atomic formulae:

• (v,f) doppel-satisfies h=k (where h and k are variables-or-names) iff v(h)=v(k) and f(h)=f(k)
• (v,f) doppel-satisfies Q(h₁,...,h_n) where Q is other than identity iff (I(h₁),...,I(h_n))∈I(Q).

And finally we can define doppel-truth: a sentence S of L is doppel-true provided that it is doppel-satisfied by every substitution and signature vector pair.

It is easy to see that if s_m is the usual sentence that asserts that there are m objects, and if D has n objects, then s_m is doppel-true if and only if m=2n. It is also easy to see that all the first order rules for quantifiers are valid for our quasi-quantifiers ∃ and ∀.

Now on to our fake dualism. We need a more complex doppelganging. Specifically, we need to divide our stock of predicates into the mental and non-mental predicates. Start with a materialist's first order language L that includes mental predicates (the materialist may think they are in some sense reducible). Add a predicate SoulOf(x,y) (we won't need to specify whether it's mental or not) which will count for us as neither mental nor non-mental. I will assume for simplicity that the mental predicates are all unary (e.g., "thinks that the sky is blue")—things get more complicated otherwise, but one can still produce the fake dualism. Now, instead of doppelganging all the objects, we only doppelgang the minded objects. Thus, our models will be triples (D,D_m,P) where D_m is a subset of D (the minded objects, in the intended interpretation). We say that a substitution and signature vector pair (v,f) is licit if and only if f(a)=1 implies v(a)∈D_m ("only members of D_m have doppelgangers"), and in all our definitions we only work with licit pairs. Moreover, our reinterpretations do not need to give any extension to the predicate SoulOf(x,y): that's handled in the semantics.

Finally, we modify doppel-satisfaction for quantifiers and predicates:

• (v,f) doppel-satisfies ∃xF iff for some u in D, (v(x/u),f(x/0)) doppel-satisfies F or for some u in D_m, (v(x/u),f(x/1)) doppel-satisfies F
• (v,f) doppel-satisfies ∀xF iff for every u in D, (v(x/u),f(x/0)) doppel-satisfies F and for every u in D_m, (v(x/u),f(x/1)) doppel-satisfies F.
• (v,f) doppel-satisfies h=k (where h and k are variables-or-names) iff v(h)=v(k) and f(h)=f(k)
• (v,f) doppel-satisfies Q(h₁,...,h_n) where Q is non-mental and other than identity iff (I(h₁),...,I(h_n))∈I(Q) and f(h₁)=...=f(h_n)=0
• (v,f) doppel-satisfies Q(h) where Q is mental iff I(h)∈I(Q) and f(h)=1
• (v,f) doppel-satisfies SoulOf(h,k) iff v(h)=v(k), f(h)=1 and f(k)=0.

And then we say we have doppel-truth of a sentence when every licit pair is satisfied.

The intended materialist doppel-interpretation (I,f) consists of the usual materialist interpretation I of the names and predicates other than Soul(x) and that gives to Soul(x) the extension of all the minded objects, sets D_m to be the set of minded objects, plus has a signature f such that f(n)=1 where n is a name of a minded object and otherwise f(n)=0.

Now let's speak an informal version of our doppelganged materialist language. Let M be any mental predicate and Q any non-mental one. Say that a soul is any x such that ∃y(SoulOf(x,y)). Suppose "Jill" is the name of a minded object. The following sentences will be doppel-true:

• Some objects have souls.
• Every object that has a soul is a non-soul.
• Only souls satisfy M.
• No soul satisfies Q.
• Jill is a soul.
• Jill does not satisfy Q.

The doppel-language is strongly dualist. Only the souls have mental properties predicated of them and only the non-souls have non-mental properties (or stand in non-mental relations). A materialist community could stipulate that henceforth their language bears this kind of doppel-interpretation. They could then talk like dualists. But they wouldn't be dualists.. Hence the doppelganged ∃ and ∀ aren't really quantifiers.

Assume materialism. If there are n material objects, including m minded objects, then in the doppelganged language it will be true to say something like "There are n+m objects." For every one of the minded objects has a doppelganger.

Brains, souls and consciousness

1. (Premise) I am the only entity that has all the conscious states I presently have.
2. (Premise) I am breathing.
3. (Premise) My soul isn't breathing.
4. (Premise) My brain isn't breathing.
5. I am neither my soul nor my brain. (2-4)
6. Neither my soul nor my brain has all the conscious states I presently have. (1,5)
7. (Premise) If my soul or my brain is conscious, it has all the conscious states I presently have.
8. So, neither my soul nor my brain is conscious.

If my soul or my brain grounds my consciousness, it does not ground my consciousness by being conscious. It grounds my consciousness by having non-conscious states that ground my consciousness. These non-conscious states will then be more fundamental than my conscious states.

In particular, substance dualists should agree with naturalists that conscious states are non-fundamental. Only non-substance dualists, like hylomorphic dualists and property dualists, have a hope of saying that conscious states are fundamental. And of course a similar argument can be run for other mental states beside the conscious ones.

In practice, some substance dualists will say that I am my soul. If so, then I don't breathe (at most I cause breathing), I don't weigh anything, and so on.

Soul-body interaction

I have a post on soul-body interaction on Biola's Center for Christian Thought blog that may be of interest to my readers here.

A just-so story for Genesis 1-3

Consider this argument:

1. If Christianity is right, every assertion of rightly interpreted Scripture is true.
2. Genesis 1-3 is rightly interpreted literalistically.
3. The approximate truth of our best relevant science contradicts the assertions of Genesis 1-3 when these texts are interpreted literalistically.
4. Our best relevant science is approximately true.
5. So, Christianity is not right.

Liberal Christians reject (1), and often (2) as well. Young Earth Creationists either engage in revisionary science and deny (3), or they simply deny (4).

The right way out of the argument is, of course, to reject (2). But in this post I want to undercut the argument in a very different way. Basically, I will argue against (3) by offering a just-so story that is compatible with both our best science and a literalistic reading of Genesis 1-3, without scientific revisionism, scientific irrealism, or invocations of divine or demonic deception.

I am not claiming the story is true. In fact, I think it's false. It is in tension with the Thomistic view of the soul which I hold (but I think it may be logically compatible with it—but that's a longish story). As I said, the right way out is to deny (2).

The story is simple. First, everything happens exactly as it is described in Genesis 1-3 interpreted literalistically. Everything, including a light-studded dome ("firmament"), with waters above and below, creation in six days, vegetation without any sun or moon. Eve is literally taken from Adam's side, and so on. Then Adam and Eve sin, exactly as described in Genesis 3. All this happens in a universe ("Paradise") where all of this is possible by the laws of nature.

God then kicks them out of this universe. In the process, he destroys their bodies and puts their souls in stasis. But in Paradise, there was a law of nature that when the forbidden fruit is eaten, a Big Bang will occur (or this could be a miracle), initiating a 14 billion year process leading to some pretty clever apes in a universe better suited to sinners like Adam and Eve. God then takes the matter of two of these clever apes (if animals have souls, he de-souls them first, or perhaps he simply miraculously ensures that these two don't get souls) and instills Adam and Eve's souls in this matter.

And so all the science as to what has happened in the material universe since the Big Bang is right. Of course, science doesn't talk about souls.

A materialist Christian could also run a variant of this story of Adam and Eve being asleep for fourteen billion years, but it would involve some miracles in the physical world and maybe disagreement with science at one point. (Maybe Adam and Eve's brains are put in the bodies of some apes. Or maybe God is capable of so guiding indeterministic processes that there develop two apes that are just like Adam and Eve, and God can replace them with Adam and Eve.)

Of course, I don't believe these stories. But they do show that premise (3) of the anti-Christianity argument is false.

Images of the soul

I bet a lot of people when they think about the soul imagine something nebulous—a kind of glow, or gas, or force-field, or the like—permeating the body. Certainly, this is how I imagine it. It's funny that nobody imagines the soul to be like a rock. Yet, aren't both images just as much off? The nebulous something—that fails convey the stability and unity of the soul. And the rock—that fails to convey immateriality.

(I am not about to urge that one not imagine anything when thinking about the soul. When I think about mathematical entities, I do imagine physical objects—for instance, graphs—that represent them. But that only rarely leads me astray—much more often, it helps.)

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.

Spiritual sickness and spiritual death

There is a temptation for Catholics—also present for non-Catholic Christians but with different terminology—to settle for avoiding mortal sin. After all, if one has living faith and does not reject Christ's salvific grace through mortal sin, one will be saved. So why should one worry about venial sin?

Leaving aside the question of purgatory—for that is not the heart of the issue, but something more in the way of an effect of it—here is one thing that is wrong with this. In a state of mortal sin, one is bereft of living faith, of charity and of Christian hope. One is spiritually dead. If one is not a state of mortal sin, then one is spiritually alive. But surely we are not merely satisfied with being alive.

It would be silly to say: "I shall not go to the doctor. Yes, I have a great big ulcer, but after all, I am alive, and that is all that matters." While there may be contexts where it is appropriate to shout with joy "I am alive!" as if that was all that mattered—for instance, right after one's life (spiritual or physical) has just been saved. But as regards the body, we do not just want life. We want a life of health. One can be alive, but very ill, close to death. There is still reason to have the joy of life—there is a qualitative difference between that life and death—but that is not what we aspire to. (Here, of course, one recalls what Socrates says about how happiness is thought to require health of body and in fact requires health of soul.)

But there is a disanalogy between the physical illness of those who are physically alive and the spiritual illness of those who are spiritually alive. For while this particular physical illness may not win out, our mortal body is after all heading for the grave—perhaps unless the eschaton intervenes.[note 1] But while spiritually ill though in a state of grace, there is reason to hope—not just hope to overcome that particular illness, but to overcome them all, by the grace of Christ living in us. Thus we do have more reason to rejoice over being spiritually alive than over physically alive—but this rejoicing cannot lead to idleness, since after all, how much do we want to prolong our ill health?

Artificial Intelligence and Personal Identity

Today at Baylor's Science and Human Nature conference I am giving a talk where I argue that absurdities follow from the assumption that a robot is a person. For a quick argument, note that the question of how many persons there are ought always to have an objective answer, but the question of how many robots there does not always have an objective answer. (Think of a larger robot made up of smaller ones, for instance.)