Classical theists should take externalism in philosophy of mind more seriously

After Kripke, pretty much everyone nowadays accepts moderate mental externalism: the content of our thoughts depends on the extra-mental world. On earth where the predominant colorless liquid with such-and-such properties, the word “water” refers to water (i.e., H₂O), while on twin-earth where it is XYZ that has these properties, the word “water” refers to XYZ, and the thoughts that are expressed with sentences using “water” have a content involving water and XYZ, respectively, even if they are grounded in the same internal states of the brain and/or soul.

But there are stronger forms of mental externalism. First, we could have much more radical mental content externalism. Perhaps in one world the very same internal state means that there is water in the lake and in another world it means that the lake is dry but full of elephants. Second, we could have externalism about the subjective experience—the qualia—of mental activity. Thus, perhaps, depending on how extra-mental reality is, in one world one has the experience of seeing a red cube and in other that of smelling a daisy, despite having the same internal state in both worlds.

These stronger forms of mental externalism are rather counterintuitive and strange.

The point of this post, however, is that those of us who accept classical theism should take them much more seriously than we have tended to do. For on classical theism, God is simple and yet knows contingent extra-mental reality. This means that in different worlds God has different knowledge, while yet by simplicity remaining exactly internally the same. Hence we have an extremely strong mental content externism in the case of God: the very same state could mean that the universe consists of a lake with water and that it consists of a mountain covered by elephants. Moreover, if we add—as surely we should—that God’s knowledge is a conscious “vision” of reality, we also have to admit that externalism about subjective exerience is true of God.

Now, we cannot simply go from these externalisms being true of God to their being true of us. But I think we should take the externalisms in our case to be a very serious possibility.

A first attempt at exploring this kind of externalism in the case of subjective experience is here.

Mental properties and union dualism

Suppose union dualism is true (I am a composite consisting of soul and body) and I am looking at a red cube. Then I am consciously aware of a red cube in virtue of my soul having some property instance M. Now, this property instance M makes me have a perception of a red cube, but it doesn’t make my soul have a perception as a red cube, because otherwise two things have that perception, and we have the too many thinkers problem. Thus considered as a property of my soul, we shouldn’t describe M as “the property (instance) of perceiving a red cube”. Instead, it is the soul’s property (instance) of “being an x such that x’s possessor perceives a red cube”.

Is M also a property (instance) of me, or just of my soul? Indeed, can the same thing be a property (instance) of two things? Maybe. It sure seems that a watermelon is partly red because its flesh is red, and yet we shouldn’t multiply instances or tropes of red, so there is a single instance of red—which makes the part red, thereby making the whole partly red. Thus, the redness can be thought of as both a property of the flesh and of the watermelon. It is an immediate property of the flesh and a mediate property of the watermelon. As a property of the flesh, it is the property of being red. As a property of the watermelon, it is the property of being partly red. Perhaps, though, this is a merely semantic question. We might say that “property possession” is immediate property possession or that it is mediate or immediate property possession.

In any case, insofar as M is a property of my soul, there is a sense in which it is a mental property and a sense in which it is not. As a property of the soul, it is not a property of thinking, perceiving, believing or of any other of the usually named mental activities, because the soul engages in none of these, since these are activities of me, not of my soul. But at the same time, it is a property that makes me perceive, and hence can be considered mental in that sense. Perhaps we might want to say this: M is a proto-mental property, and to have a mental property is to have a soul that has the requisite proto-mental property.

In any case, I think the above considerations show that arguing for Cartesian dualism—the view that I am a soul—on the grounds that the soul has mental properties and yet there are not two thinkers is too quick (Merricks argues like that here). In one sense, the soul has mental properties, but these properties do not turn the soul, only its possessor, into a thinker. In another sense, the soul has only proto-mental properties.

Maybe it’s a bit like this. Water isn’t moist, but it makes other things moist. Water does this by having some property—a property the physical chemist will have more to say about—in virtue of which anything that has the right association with the water is moist.

Fine-tuning of both physical and bridge laws

A correspondent pointed me to a cool paper by Neil Sinhababu arguing that the theist can’t consistently run a fine-tuning argument on which it is claimed that it is unlikely that the constants in the laws of physics permit intelligent life, because if God exists, then for any constants in the physical laws God can make psychophysical bridge laws that make sure that there is intelligent life. By choosing the right bridge laws, God can make a single electron be conscious, after all. Thus any set of constants in laws of physics is compatible with intelligent life.

A quick response is that in the context of the fine-tuning argument, by “intelligent life” we should probably mean “intelligent biological life”. For instance, angels and conscious electrons don’t count, as they aren’t biological. And in fact, I think, in practice the fine-tuning argument is more about biological life than intelligent life as such. This suggests, however, that proponents of the fine-tuning argument should be clearer here. In particular, we (I am one of the proponents) should emphasize that there is a great value in the existence of biological life, and especially intelligent biological life, and this value is not found in intelligent non-biological life. This value is why a perfect being is not unlikely (or at least not extremely unlikely) to fine-tune the universe to for such life.

Second, I think Sinhababu’s argument points to a more subtle way to formulate the fine-tuning thesis. What’s fine-tuned is not the laws of physics alone, but the combination of the laws of physics and the bridge laws, and they are fine-tuned together in such a way as to ensure that there is neither too little nor too much intelligent life. For instance, a set of psychophysical laws where any computation isomorphic to the kinds of computations our brains results in mental functioning like ours would result not just in panpsychism but omnisapientism—everything around us is sapient. For with some cleverness we can find an isomorphism between the states of a single particle and the states of the brain that preserves causation. But omnisapientism isn’t very good: it damages the significance of morality if everything we do creates and destroys vast numbers of sapient beings.

An argument for dualism from Special Relativity and unity of consciousness

Here’s a valid argument:

1. There is always an absolute fact about whether two conscious states are hosted simultaneously.

2. If the mind is physical, there is not always an absolute fact about whether two conscious states are hosted simultaneously.

3. So, the mind is not physical.

Why believe (2)? Well, if the mind is physical, it is a brain—that’s by far and away our best physical theory of the mind. The brain is spatially extended, and it is very plausible that different brain regions are involved in different conscious states. But now we can imagine that one conscious state ends almost when another begins, so that the overlap time between the two conscious states is very, very small—say, a picosecond. If the brain brain regions involved in the two conscious states are sufficiently different (more precisely, if their convex hulls differ sufficiently in comparison to the distance light travels during the overlap time), then there will also be some reference frame in which the two conscious states do not temporally overlap. Hence, it depends on reference frame whether the two conscious states overlap, and there is no fact of the matter about simultaneity of the conscious states.

If I were a physicalist, I think I would attack (1).

Octopuses, aliens, squirrels and AI

I’ve been toying with an argument for dualism along these lines:

1. Octopuses are conscious.

2. Technologically advanced aliens are or would be conscious.

3. Squirrels are conscious.

4. Current LLMs are not conscious.

Claims 1–3 require a pretty strong multiple realizability. On materialism, our best such multiple realizability is a functionalism. But it is likely that our current LLMs have more sophisticated general intelligence than squirrels. Thus, a functionalism that makes 1–3 true also violates 4.

Dualism, on the other hand, can allow for all of 1–4 by supposing the hypothesis that all and only intellectually sophisticated living things have souls.

Could a physicalist do the same? I think the difficulty is that life is very fuzzy on physicalism, in a way in which consciousness should not be. On dualism, however, we can suppose that God or the laws of nature have a seemingly arbitrary threshold of what life is.

Gaze dualism and omnisubjectivity

I have toyed with a pair of theories.

The first is what I call gaze-dualism. On gaze-dualism, our sensory conscious experiences are constituted by a non-physical object—the soul—“gazing” at certain brain states. When the sensory data changes—say, when a sound goes from middle A to middle C—the subjective experience changes. But this change need not involve an intrinsic change in the soul. The change in experience is grounded in a change in the gazed-at brain state, a brain state that reflects the sensory data, rather than by a change in the gazing soul. (This is perhaps very close to Aquinas’ view of sensory consciousness, except that for Aquinas the gazed-at states are states of sense organs rather than of the brain.)

The second is an application of this to God’s knowledge of contingent reality. God knows contingent reality by gazing at it the way that our soul gazes at the brain states that reflect sensory data. God does not intrinsically change when contingent reality changes—the change is all on the side of the gazed-at contingent reality.

I just realized that this story makes a bit of progress on what Linda Zagzebski calls “omnisubjectivity”—God’s knowledge of all subjective states. My experience of hearing a middle C comes from my gazing at a brain state B_C of my auditory center produced by nerve impulses caused by my tympanic membrane vibrating at 256 Hz. My gaze is limited to certain aspects of my auditory center—my gaze tracks whatever features of my auditory center are relevant to the sound, features denoted by B_C, but does not track features of my auditory center that are not relevant to the sound (e.g., the temperature of my neurons). God’s gaze is not so limited—God gazes at every aspect of my auditory center. But in doing so, he also gazes at B_C. This does not mean that God has the same experience as I do. My experience is partly constituted by my soul’s gaze at B_C. God’s experience is partly constituted by God’s gaze at B_C. Since my soul is very different from God, it is not surprising that the experiences are different. However, God has full knowledge of the constituents of my experience: myself, my gaze, and B_C, and God’s knowledge of these is basically experiential—it is constituted by God’s gazing at me, my gaze, and B_C. And God also gazes at their totality. This is, I think, all we need to be able to say that God knows my sensory consciousness states.

My non-sensory experiences may also be constituted by my soul’s gazing at a state of my brain, but they may also be constituted by the soul’s gazing at a state of the soul. And God gazes at the constituents and whole again.

Dualism, humans and galaxies

Here is a mildly interesting thing I just noticed: given dualism, we cannot say that we are a part of the Milky Way galaxy. For galaxies, if they exist at all, are material objects that do not have souls as parts.

Brains, bodies and souls

There are four main families of views of who we are:

1. Bodies (or organisms)

2. Brains (or at least cerebra)

3. Body-soul composites

4. Souls.

For the sake of filling out logical space, and maybe getting some insight, it’s worth thinking a bit about what other options there might be. Here is one that occurred to me:

5. Brain-soul (or cerebrum-soul) composites.

I suppose the reason this is not much (if at all) talked about is that if one believes in a soul, the body-soul composite or soul-only views seem more natural. Why might one accept a brain-soul composite view? (For simplicity, I won’t worry about the brain-cerebrum distinction.)

Here is one line of thought. Suppose we accept some of the standard arguments for dualism, such as that matter can’t be conscious or that matter cannot think abstract thoughts. This leads us to think the mind cannot be entirely material. But at the same time, there is some reason to think the mind is at least partly material: the brain’s activity sure seems like an integral part of our discoursive thought. Thus, the dualist might have reason to say that the mind is a brain-soul composite. At the same time, there is a Cartesian line of thought that we should be identified with the minimal entity hosting our thoughts, namely the mind. Putting all these lines of thought together, we conclude that we are minds, and hence brain-soul composites.

Now I don’t endorse (5). The main ethical arguments against (2) and (4), namely that they don’t do justice to the deep ethical significance of the human body, apply against (5) as well. But if one is not impressed by these arguments, there really is some reason to accept (5).

Furthermore, exploring new options, like the brain-soul composite option, sometimes may give new insights into old options. I am now pretty much convinced that the mind is something like the brain plus soul (or maybe cerebrum plus intellectual part of soul or some other similar combination). Since it is extremely plausible that all of my mind is a part of me, this gives me a new reason to reject (4), the view that I am just a soul. At the same time, I do not think it is necessary to hold that I am just a mind, so I can continue to accept view (3).

The view that the mind is the brain plus soul has an interesting consequence for the interim state, the state of the human being between death and the resurrection of the body. I previously thought that the human being in the interim state is in an unfortunately amputated state, having lost all of the body. But if we see the brain as a part of the mind, the amputated nature of the human being in the interim state is even more vivid: a part of the human mind is missing in the interim state. This gives a better explanation of why Paul was right to insist on the importance of the physical resurrection—we cannot be fully in our mind without at least some of our physical components.

More fun with monochrome Mary

Here’s a fun variant of the black-and-white Mary thought experiment. Mary has been brought up in a black-and-white environment, but knows all the microphysics of the universe from a big book. One day she sees a flash of green light. She gains the phenomenal concept α that applies to the specific look of that flash. But does Mary know what green light looks like?

You might think she knows because her microphysics book will inform her that on such-and-such a day, there was a flash of green light in her room, and so she now knows that a flash of green light has appearance α. But that is not quite right. A microphysics book will not tell Mary that there was a flash of green light in her room. It will tell her that there was a flash of green light in a room with such-and-such physical properties. Whether she can deduce from these properties and her observations that this was her room depends on what the rest of the universe is like. If the universe contains Twin Mary who lives in a room with exactly the same monochromatically observable properties as Mary’s room, but where at the analogous time there is a flash of blue light, then Mary will have no way to resolve the question of whether she is the woman in the room with the green flash or in the room with the blue flash. And so, even though Mary knows all the microphysical facts about the world, Mary doesn’t know whether it is a green flash or a blue flash that has appearance α.

This version of the Mary thought experiment seems to show that there is something very clear, specific and even verbalizable (since Mary can stipulate a term in her language to express the concept α, though if Wittgenstein is right about the private language argument, we might require a community of people living in Mary’s predicament) that can remain unknown even when one knows all the microphysical facts and has all the relevant concepts and has had the relevant experiences: Whether it is green or blue light that has appearance α?

This seems to do quite a bit of damage to physicalism, by showing that the correlation between phenomenal appearances and physical facts is a fact about the world going beyond microphysics.

But now suppose Joan lives on Earth in a universe which contains both Earth and Twin Earth. The denizens of both planets are prescientific, and at their prescientific level of observation, everything is exactly alike between Earth and Twin Earth. Finer-grained observation, however, would reveal that Earth’s predominant surface liquid is H₂O while Twin Earth’s is XYZ, but currently there is no difference. Now, Joan reads a book that tells her in full detail all the microphysical structure of the universe.

Having read the book, Joan wonders: Is water H₂O or is it XYZ? Just by reading the book, she can’t know! The reason she doesn’t know it is because her prescientific observations combined with the contents of the book are insufficient to inform her whether she lives on Earth or on Twin Earth, whether she is Joan or Twin Joan, and hence are insufficient to inform her whether the liquid she refers to as “water” is H₂O or XYZ.

But surely this shouldn’t make us abandon physicalism about water!

Now Joan and Twin Joan both have concepts that they verbalize as “water”. The difference between these concepts is entirely external to Joan and Twin Joan—the difference comes entirely from the identity of the liquid interaction with which gave rise to the respective concepts. The concepts are essentially ostensive in their differences. In other words, Joan’s ignorance of whether water is H₂O or XYZ is basically an ignorance of self-locating fact: is she in the vicinity of H₂O or in the vicinity of XYZ.

Is this true for Mary and Twin Mary? Can we say that Mary’s ignorance of whether it is a green or a blue flash that has appearance α is essentially an ignorance of self-locating facts? Can we say that the difference between Mary’s phenomenal concept formed from the green flash and Twin Mary’s phenomenal concept formed from the blue flash is an external difference?

Intuitively, the answer to both questions is negative. But the point is not all that clear to me. It could turn out that both Mary and Twin Mary have a purely comparative recognitive concept of “the same phenomenal appearance as that flash”, together with an ability to recognize that similarity, and with the two concepts being internally exactly alike. If so, then the argument is unconvincing as an argument against physicalism.

The epistemic gap and causal closure

In the philosophical literature, the main objection to physicalism about consciousness is the epistemic gap: the alleged fact that full knowledge of the physical does not yield full knowledge of the mental. And one of the main objections to nonphysicalism about consciousness is causal closure: the alleged fact that physical events, like our actions, have causes that are entirely physical.

There is a simple way to craft a theory that avoids both objections. Simply suppose that mental states have two parts: a physical and a non-physical part. The physical part of the mental state is responsible for the mental state’s causal influence on physical reality. The non-physical part explains the epistemic gap: full knowledge of the physical world yields full knowledge of the physical part of the mental state, but not full knowledge of the mental state.

Something Mary doesn't know

Here is something our old friend Mary, raised in a black and white world, cannot know simply by knowing all of physics:

1. What are the necessary and sufficient physical conditions for two individuals to be in exactly the same phenomenal state?

Of course, her being raised in a black and white world is a red herring. I think nobody can know the answer to (2) simply by knowing all of physics.

Some remarks:

• Knowledge of the answer to (1) is clearly factual descriptive knowledge. So responses to the standard knowledge argument for dualism that distinguish kinds of knowledge have no effect here.

• The answer to (1) could presumably be formulated entirely in the language of physics.

• Question (1) has a presupposition, namely that there are necessary and sufficient physical conditions, but the physicalist can’t deny that.

• A sufficient conditions is easy given physicalism: the individuals have the exact same physical state.

• Dennettian RoboMary-style simulation does not solve the question. One might hope that if you rewrite your software, you can check if you have the same qualia before and after the rewrite. But the problem is that you can only really do exact comparisons of qualia that you see in a unified way, and there is insufficient unification of your state across the software rewrite.

If materialism is true, we can't die in constant pain

Here is an unfortunate fact:

1. The last minute of your life can consist of constant conscious pain.

Of course, I think all pain is conscious, but I might as well spell it out. The modality of the “can” in this post will be something fairly ordinary, like some sort of nomic possibility.

Now say that a reference frame is “ordinary for you” provided that it is a reference frame corresponding to something moving no more than 100 miles per hour relative to your center of mass.

Next, note that switching between reference frames should not turn pain into non-pain: consciousness is not reference-frame relative. Thus:

2. If the last minute of your life consists of constant conscious pain, then in every reference frame that is ordinary for you, in the last half-minute of your life you are in constant conscious pain.

Relativistic time-dilation effects of differences between “ordinary” frames will very slightly affect how long your final pre-death segment of pain is, but will not shorten that segment by even one second, and certainly not by 30 seconds.

Next add:

3. If materialism is true, then you cannot have a conscious state when you are the size of a handful of atoms.

Such a small piece of the human body is not enough for consciousness.

But now (1)–(3) yield an argument against materialism. I have shown here that, given the simplifying assumption of special relativity, in almost every reference frame, and in particular in some ordinary frames, your life will end with you being the size of a handful of atoms. If materialism is true, in those frames towards the very end of your life you will have to exist without consciousness by (3), and in particular you won’t be able to have constant conscious pain (or any other conscious state) for your last half-minute.

Unconscious aliens

Lately I’ve been starting my philosophy of mind course with Carolyn Gilman’s short story about unconscious but highly intelligent aliens.

We can imagine such aliens having thoughts, beliefs, concepts, representational and motivational states. After all, we have beliefs even when totally unconscious, and we have subconscious thoughts, concepts, as well as representational and motivational states.

I’ve wondered what unconscious aliens would think about our philosophical arguments about physicalism and consciousness. They might not have the concept of consciousness or of an experiential state, but they could have the concept of “that special mode of representing reality that humans have and we don’t”. And so now I ask myself: Would these aliens have any reason to think that consciousness-based arguments for dualism have any force? Would they have any reason to think that “special mode” is a non-physical mode?

Of course, the aliens might be convinced of dualism on the basis of intentionality arguments. But would something about humans give them additional evidence of dualism about humans?

The aliens shouldn’t be surprised to discover that humans when awake have some ways of processing inputs that they themselves don’t, nor should that give any evidence for dualism. Neither should the presence of some special “phenomenological” vocabulary in humans for describing such processing.

But I think what should give the aliens some evidence is the conviction that many humans have that their “experiences” lack physical properties, that they are categorically different from physical properties and things. If someone describes an object of sensory perception as lacking color, that gives one reason to think the object indeed lacks color. If someone describes the object of introspective perception as lacking charge or mass, that gives one reason to think the object indeed lacks charge or mass.

The aliens would need to then consider the fact that some people have the conviction and others do not, and try to figure out which ones are doing a better job learning from their introspection.

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.

Ways out of the closure argument for physicalism

One of the main arguments for physicalism is based on the closure principle:

1. Any physical event that has a cause has a physical cause.

It is widely thought that it follows from (1) that:

2. If a physical event has a nonphysical cause, the event is overdetermined.

And hence in the absence of systematic overdetermination, mental causes must be physical.

But (2) doesn’t follow from (1). There are at least three ways for an event E to have two sufficient causes A and B:

• overdetermination

• chaining: A causes B which causes E or B causes A which causes E

• parthood: A causes E by having B as a part which causes E, or B causes E by having a part A which causes E.

Let’s think a bit about how the chaining and parthood options might avoid physicalism in the case of mental causation and yet allow for closure.

Option I: Nonphysical-physical-physical chaining: A nonphysical event M causes a physical event P which causes a physical event E. This can’t be the whole story for how we respect closure. For by closure, P will need a physical cause P₂, and so it is looking like P is going to be overdetermined, by M and P₂. But that does not follow without further assumptions. For we could have the following scenario:

• E is caused by an infinite chain of physical causes which chain is causally preceded by M, namely: P ← P₂ ← P₃ ← ... ← M, with infinitely many physical events in the “…”.

This scenario requires the possibility of an infinite sequence of causal means, contrary to causal finitism, and hence is unacceptable to me. But those who are less worried about infinite chains of causes should take this option seriously. Note that this option is reminiscent of Kant’s view on which our noumenal selves collectively cause the physical universe as a whole.

Option II: Physical-nonphysical-physical chaining: Here, the physical event P causes E by having a mental event as an intermediate cause. This option exploits a loophole in the closure principle as it is normally formulated: nothing in the closure principle says that the physical cause can’t operate by means of a nonphysical intermediary. Granted, that’s not how we normally think of physical causes as operating. But there is nothing incoherent about the story.

Option III: Physical parts of larger events: A physical event E is caused by a physical event P, and the physical event P is itself a part of a larger event M which is only partly physical. One might object that in this case it’s only P and not the larger event that counts as the cause. But that’s not right. If someone dies in the battle of Borodino, then at least three causes of death can be given: a shot being fired, the battle of Borodino, and the War of 1812. The shot is a part of the battle, and the battle is a part of the war. One particular way to have Option III is this: a quale Q is constituted by two components, a brain state B (say, a state of the visual cortex) and a soul state S of paying attention to the brain system that exhibits B, with B being the causally efficacious part of the Q. So a physical event—say, an agent’s making an exclamation at what they saw—counts as caused by the physical event B and the event Q which is not physical, or at least not completely physical.

One might object, however, that by “nonphysical”, one means entirely nonphysical, so Q’s having a nonphysical part S does not make Q nonphysical. If so, then we have one last option.

Option IV: Some or all physical causes cause their effects by having a nonphysical part that causes the event. That nonphysical part could, for instance, be an Aristotelian accidental or substantial form. Thus, here a physical event E is caused by a physical event by means of its nonphysical part M.

What if one objects that “physical” and “nonphysical” denote things that are purely physical and nonphysical, and neither can have a part that is the other? In that case, we have two difficulties. First, the closure principle is now stronger: it requires that a physical event that has a cause always has a purely physical cause. And we have a serious gap at the end of the argument. From closure at most we can conclude that a physical event doesn’t have a purely nonphysical cause. But what if it has a partly physical and partly nonphysical cause? That would be enough to contradict physicalism.

Physicalism and the progress of science

People sometimes use the progress of science to argue for physicalism about the mind. But it seems to me that Dostoevskii made more progress in understanding the human mind by existential reflection than anybody has by studying the brain directly. More generally, if we want to understand human minds, we should turn to literature and the spiritual masters rather than to neuroscience.

Thus, any argument for physicalism about the mind from the progress of science is seriously flawed. And perhaps we even have some evidence against physicalism. For it is a surprising fact that we learn more about the mind by the methods of the humanities than by study of the brain if the mind is the brain.

Animalist functionalism

The only really plausible hope for a materialist theory of mind is functionalism. But the best theory of our identity, materialist or not, is animalism—we are animals.

Can we fit these two theories together? On its face, I think so. The thing we need to do is to make the functions defining mental life be functions of the animal, not of the brain as such. Here are three approaches:

1. Adopt a van Inwagen style ontology on which organisms exist but brains do not. If brains don’t exist, they don’t have functions.

2. Insist that some of the functions defining mental life are such that they are had by the animal as a whole and not by the brain. Probably the best bet here are the external inputs (senses) and outputs (muscles).

3. Modify functionalism by saying that mental properties are properties of an organism with such-and-such functional roles.

I think option 2 has some special difficulties, in that it is going to be difficult to define “external” in such a way that the brain’s connections to the rest of the body don’t count as external inputs and outputs and yet we allow enough multiple realizability to make very alien intelligent life possible. One way to fix these difficulties with option 2 is to move it closer to option 3 by specifying that the external inputs and outputs must be inputs and outputs of an organism.

Options 1 and 3, as well as option 2 if the above fix is used, have the consequence that strong AI is only possible if it is embedded in a synthetic organism.

All that said, animalist functionalism is in tension with an intuition I have about an odd thought experiment. Imagine that after I got too many x-rays, my kidney mutated to allow me exhibit the kinds of functions that are involved in consciousness through the kidney (if organism-external inputs and outputs are required, we can suppose that the kidney gets some external senses, such as a temperature sense, and some external outputs, maybe by producing radio waves, which help me in some way) in addition to the usual way through the brain, and without any significant interaction with the brain’s computation. So I am now doing sophisticated computation in my kidney of a sort that should yield consciousness. On animalist functionalism, I should now have two streams of consciousness: one because of how I function via the brain and another because of how I function via the mutant kidney. But my intuition is that in fact I would not be conscious via the kidney. If there were two streams of consciousness in this situation (which I am not confident of), only one would be mine. And that doesn’t fit with animalist functionalism (though it fits fine with non-animalist functionalism, as well as with animalist dualism, since the dualist can say that the kidney’s functioning is zombie-like).

Given that functionalism is the only really good hope we have right now for a materialist theory of mind, if my intuition about the mutant kidney is correct, this suggests that animalism provides evidence against materialism.

Physicalism, persons, fission and eliminativism

People are philosophically unhappy about nonlocality in quantum mechanics. It is interesting to me that there is an eerily similar nonlocality on standard psychological theories of personal identity. For on those theories:

1. You survive if your memories survive in one living person.

2. You perish if your memories fission between more than one living person.

Now imagine that your brain is frozen, the data from it is destructively read, and then sent to two different stations, A and B, located in opposite directions five light minutes away from your original brain. At each station, a coin is simultaneously flipped (say, in the rest frame of your original brain). If it’s heads (!), the data is put into a freshly cloned brain in a vat, and if it’s tails, the data is deleted.

On a psychological theory, if both coins land heads you perish by (2). But if exactly one coin lands heads, you survive at that station. So whether you exist at one station depends on what happens simultaneously (according to one frame) at a station ten light minutes away.

Note, however, that this is not explicable via quantum nonlocality, because quantum nonlocality depends on entanglement, and there is no relevant entanglement in this thought experiment. It would be a nonlocality beyond physics.

I think one lesson here is that ostensibly physicalist or physicalist-friendly theories of persons or minds can end up sounding oddly dualist. For if dualism were true, it wouldn’t be utterly surprising if facts about where your soul reappears could have a faster-than-light dependence on far away events, since souls aren’t governed by the laws of physics. Similarly, on functionalism plus psychological theories of personal identity, you could move between radically different physical embodiments or even between a physical embodiment and a nonphysical realization. That, too, sounds rather like what you would expect dualism to say.

If I were a physicalist, I would perhaps be inclined to be drawn by these observations towards eliminativism about persons. For these observations suggest that even physicalist pictures of the person may be too deeply influenced by the dualist roots of philosophical and theological reflection on personhood. If these roots are seen as intellectually corrupt by the physicalist, then it should be somewhat attractive to deny the existence of persons.

Distancing oneself from one's brain

It can be quite useful for someone suffering from a variety of brain conditions, such as obsessive compulsive disorder, to deliberately distance themselves from their brain’s unfortunate doings, by saying to themselves things like: “That’s not me, just my brain.”

If physicalism is true, then brains are either identical with us or at least are the core of who we are. But “That’s not me, just me” is a contradiction while “That’s not me, just the core of my being” isn’t much of a distancing. A similar issue arises in second and third person contexts: if physicalism is true, one must admit brain problems to be grounded in that which is at the core of the other’s being.

The dualist, on the other hand, can pull off the distancing much more easily: “That’s not my soul, just my brain” makes perfect sense. An impairment in the brain is just an impairment of a body part, albeit one of the most important ones.

Of course, that something is a helpful way of thinking does not prove that it’s true. But it is an insight from the beginnings of Western philosophy that truth is generally better for us than falsehood, and so that something is a helpful way of thinking is some evidence that it is true. We may, thus, have some evidence for dualism here.

Fading knowledge of qualia

I am one of those people who do not have vivid memories of pains.

Suppose I stub my toe. While the toe is hurting, I know what the toe’s hurting feels like. After it stops hurting, for a while I still know what that felt like. But I know it less and less well as my memory fades, until eventually I know very little how it felt like. The whole process might take only a few minutes.

Thus, that mysterious “knowing what it’s like” involving qualia is something that comes with a parameter that varies as to how well you know it.

This should worry physicalists. Thin physicalists should worry because it doesn’t seem that the fading corresponds to any knowledge of the underlying physical reality. Thick physicalists who think that Mary just acquires a new recognitional concept when she sees red should worry, because it does not seem that there is any gradual loss of a concept. I continue to have the same “that experience” concept (the demonstrative “that” points to the same past experience, and does so in a first-personal way) and the recognitional abilities it enables (I can tell if another pain is like that one or not), even as my knowledge of what “that experience” is like fades.

It’s also not completely clear what a dualist should say about the fading of the knowledge. Normally, when knowledge fades, what happens is either that we lose details (as when I forget much of what I once learned in school about the Metis uprising), or we find the dispositional knowledge harder to make occurrent. But the fading is neither of these. Maybe what is happening is that our present knowledge becomes a less good representation of what it is the knowledge of.