Zombies Are Impossible

Nonphilosophical Zombies

No, not those zombies! They aren’t merely possible, they are actual, as you can see.

Rather, our topic today is philosophical zombies, beings that are physically identical to us but without conscious experience. Thus, a zombie version of yourself, for instance, would be atom-for-atom identical to you. It would share all of your behavioral dispositions: it would walk like you, talk like you, have the same tendencies to be angry, happy, or sad as you, report any information that you are able to report, and perform any tasks that you are able to perform. It would also remember everything that you can remember, know everything that you know, and it would have all the same politics and cultural attitudes and biases as you. At least, it would do all these things as near as we could tell. It would be behaviorally and neurophysiologically identical to you. There would be no way for another person to tell that your zombie twin was not you merely by comparing you with it, no matter what tests he might arrange. Nevertheless, your zombie twin would not be the same as you, because it would not have consciousness. That is, it would not have subjective experience. In the phrase widely adopted from Thomas Nagel’s well-known essay, “What Is It Like to Be a Bat?”, there would be nothing it is like to be your zombie twin.

Philosophical zombies are a way to make vivid an old philosophical argument, going back at least to Descartes, known as the Conceivability Argument. In the present version, the idea is that it is conceivable that the world could be just as it is physically down to the last elementary particle, but without conscious experience. That is, we could have had the Big Bang and the evolution of the universe just as it is, including the evolution of life on earth and the human species, and physically everything would be just as it is today, including all of us having discussions just like this one, although none of us nor any other beings have conscious experience. By conceivable, I mean there is no contradiction in this scenario and no reason that science can discover, whether physical, psychological, or otherwise, why it could not have happened. If this scenario is conceivable, then it seems we must conclude that consciousness is epiphenomenal: it is nonphysical, it cannot be explained by the physical, and its presence or absence makes no difference to the causal, functional, or physical order of nature.

Although he did not originate the idea of a philosophical zombie, present-day discussion of zombies is due mainly to David Chalmers, who describes them in his 1996 book, The Conscious Mind. Here is a web page by Chalmers that briefly introduces philosophical zombies and provides references to some older literature (i.e., 1990s). Here is an excellent brief write-up, very short. (It is included in Rosen et al., eds., The Norton Introduction to Philosophy, 2nd Edition, if anyone happens to have that lying around). My discussion in this post is based on the idea of a zombie as deployed by Chalmers.

Why should we accept that zombies are conceivable? Consider the example of bat echolocation employed by Nagel in his above-mentioned essay. Bats can fly in the dark, avoiding walls and trees and finding insects to eat by emitting high pitched squeaks that are reflected from the surrounding objects and picked up by the bat’s hearing. These reflected sounds are of sufficiently high frequency to permit the bat’s auditory cortex to form a cognitive map of its immediate environment good enough for flight navigation. Thus, the bat can literally hear the layout of its environment well enough to negotiate tree branches and snag bugs out of the air! And we understand perfectly well how this is done, and we could in principle map the process down to the last synapse in the bat’s brain. But doing so would evidently be no help to us in knowing what it’s like to hear the layout of our environment the way the bat does. It would be like seeing with our ears. It is telling that even the most detailed scientific understanding of echolocation would yield no insight into what it’s like. More importantly, even the most detailed scientific understanding makes no reference to what it’s like. The scientific account of echolocation refers to sound waves, their frequency, their reflection, the structure and dynamics of the bat’s ears and auditory receptors, the bat’s neural pathways, patterns of activation, motor control, and so forth. The physics of sound and the anatomy and physiology of the bat are sufficient to explain echolocation. There is no need—apparently, there is no place—to discuss what it’s like for the bat to use echolocation, even if the physiology could give us some insight into what it’s like, which evidently it can’t.

Therefore, if there were nothing it’s like for a bat to use echolocation, this would make no difference. It is conceivable that a bat could be a zombie. And if this is true of the bat, it is true of us, too. What goes for echolocation goes equally well for vision and, apparently, every other human faculty. We may not notice this, because we know what it’s like to employ vision and all our other faculties, and we take for granted that, say, what it’s like to see things is important to our use of vision. But if space aliens—who did not have vision—were to come to Earth and study us as we study bats, they would come to the analogous conclusion: human vision is explained entirely by the physics of light and by human anatomy and physiology. There would be no need, and apparently no place, to discuss what vision is like for humans. Therefore, human zombies are conceivable.

This is a remarkable conclusion! I don’t know about you, but I feel very strongly that if there were nothing it was like for me to see things, I would notice!

Chalmers accounts for the difficulty of explaining consciousness by contrasting it with the usual method of explaining abilities and functions. This usual method is to identify the underlying mechanism by which the ability or function is realized. For example, the concept of genes was introduced long before DNA was discovered. Genes were proposed to be the means by which an organism’s traits are encoded and this information passed from parent to offspring in reproduction. However, when this concept was introduced, people had no idea how this was done or what structures in the body corresponded to genes. Later, it was discovered that the encoding and transmission of traits takes place in DNA molecules. In this way, it was discovered that genes are DNA.

What enabled this discovery was the existence of a functional definition of the gene. Given a functional definition, people could search for what mechanism realizes that function. When they find that mechanism, they will have found the gene. It is essentially the same procedure by which we discovered that heat is mean molecular kinetic energy and that lightning is electrostatic discharge, and by which we will eventually discover what memory is in the brain, and face recognition, and speech perception, etc.

But apparently this procedure will not work for consciousness. The reason is that we lack a functional specification of consciousness. Everything that we can functionally specify is a mental ability, like echolocation, vision, memory, speech, etc. And it seems that we can explain these completely, as in the examples of echolocation and vision, without reference to consciousness—to what they’re like or to their being like anything at all. After we have given a complete explanation of any mental ability you like in physiological terms, it seems we will always still be able to ask, “yes, but why is this accompanied by consciousness?” This implies that consciousness is not an ability. And this implies in turn that consciousness is beyond the reach of scientific explanation. If so, then—since all our mental abilities can be explained without reference to consciousness—zombies are conceivable.

Now, I find it difficult to believe that there could be a zombie version of me. I don’t think I could function without consciousness, and therefore neither could zombie-me. But it is not obvious how to reply to the arguments just presented.

One indication of trouble for Chalmers’s position is the evident contradiction between his claims, on the one hand, to have direct knowledge of his conscious experiences, and on the other, that a zombie would think it has conscious experiences. For instance, the second sentence of his well-known article, “Facing Up to the Problem of Consciousness,” reads, “There is nothing that we know more intimately than conscious experience.” Yet in his first published discussion of zombies, “Self-Ascription without Consciousness: A Case Study,” he writes, “qualia [i.e., qualities of conscious experiences] don’t seem to play a primary role in the process by which we ascribe qualia to ourselves! ([A zombie-me,] after all, ascribes to himself the same qualia; it’s just that he’s wrong about it.)” Thus, according to Chalmers, zombie-me attributes the same consciousness to himself that I do. And zombie-me’s attributions must be sincere, since we are functionally identical. Evidently, then, zombie-me doesn’t know he’s a zombie. How, then, do I know I’m not? It seems that, by Chalmers’s own admission, we do not know intimately our conscious experience.

However, I doubt that Chalmers would be willing to give up the claim that we are each acquainted with our own conscious experience. In order for there to be “problem of consciousness” to face up to, consciousness must be a datum. But this implies that there is something wrong with the zombie idea. If we know as a matter of acquaintance that we are conscious, then a zombie should know in the same way that it isn’t. Therefore, what I and zombie-me know, think, say, etc., will be different, which is contrary to the conception of a zombie. Functionally identical zombies do not seem to be conceivable, after all.

Can we put our finger on what has gone wrong? What justifies the alleged conceivability of functionally identical zombies is the claim that consciousness is not a function. That’s why a being could be physically identical to me, yet lack consciousness, and still be functionally identical to me. It’s also what justifies the claim that consciousness cannot be scientifically explained. Consciousness plays no functional or causal role; and we cannot find the mechanism that realizes a role that does not exist. What we must do, then, is identify the role that consciousness plays in our mental life. What does consciousness do? What is it for?

It is worth pausing for a moment to emphasize the seeming intractability of this problem. It can seem inevitable that consciousness must have no functional role. For, once any functional role is specified, it will seem necessary that it be performed by a physical mechanism or structure of some kind, in accordance with physical laws, and therefore with no need of consciousness. Physics is a closed system, in the sense that there can be no nonphysical causes without violating the conservation of mass–energy. And physical causation has nothing to do with consciousness. Therefore, any functional role must be performed by a physical mechanism to which consciousness is, at best, epiphenomenal.

Can we avoid this conclusion? I have an idea, which I will attempt to explain in what remains of this post.

The problem is to find a functional role for consciousness that is not a matter of physical causation as ordinarily conceived. I suggest that the presentation of intrinsic properties is such a role. By “intrinsic properties,” I mean properties that are not relational in any essential way. For example, being larger than, being a parent, and being heavy are all relational: they consist essentially in relations between things. By contrast, being a particular shade of red is not essentially relational. To have a certain color is something an object can do all by itself. It is a property it has in itself. Therefore, it is intrinsic.

In sense-perception, such as seeing, we perceive objects having intrinsic properties and standing in certain relations. For example, I see a cat that is on the mat or a tree that is larger than the shrub next to it. The relations we perceive are real, at least to a first approximation. The cat really is on the mat, the tree is larger than the shrub, and so forth. But the intrinsic properties are not real. They do not exist at the objects in the way they appear to. Thus, the cat exhibits certain colors, the leaves of the tree look to be green, etc., but these objects do not really possess these qualities—so far as we know. To be clear, I am speaking of the color qualities as they appear to us, the color qualities you can close your eyes and imagine. These are intrinsic properties. They do not consist in relations, including causal relations, and this is the fundamental reason we do not perceive them—meaning we do not detect them by means of our sense organs. To be perceived, they would have to have causal effects. But they do not have causal effects.

To see this more clearly, think of the scientific account of color perception. The colors of object surfaces are normally perceived when ambient light is reflected from those surfaces and stimulates the cone receptors in our retinas. The object surfaces reflect certain wavelengths and absorb others, and likewise our cone receptors are stimulated by certain wavelengths much more strongly than by others. Thus stimulated, the cone receptors send electro-chemical pulses down their axons and stimulate a series of other neurons across the synapses between them in a complex chain that results eventually in color experience. Now, none of this has anything to do with the color qualities that we experience at the end of the chain. The object surfaces need have no color at all. Whether they do or not—regardless of what they are intrinsically like—their role in color perception is only to reflect certain wavelengths and absorb others. This reflectance property is a causal disposition, not an intrinsic color quality. Nor do the reflected wavelengths have color. Light is electromagnetic radiation, the same as in your microwave oven or an x-ray machine. It does not have color. Even if it did, it wouldn’t matter, because the only role of the light is to differentially stimulate the three types of cones in our retinas. Nor, obviously, do the neurons or their electro-chemical pulses or the ion exchanges across synapses have color. Color qualities are not involved in any part of this story until the very end, when—by some unknown means—they are finally experienced. Therefore, color perception is not a matter of detecting color qualities by their presence in the physical world. Rather, the color qualities are attributed somehow to perceived object surfaces by our own visual system.

What goes for color goes for all other intrinsic sensory qualities, such as sounds, tastes, smells, and felt hot and cold. They have no causal properties, and therefore they are not detected by our sense organs. Rather, they are qualities that we experience as part of our way of perceiving the world despite not being detected by our sense organs.

There is a general lesson here worth emphasizing. What we are able to know about the world outside our minds is limited to its structural and causal properties. It does not include the intrinsic properties of things. This is evident from science. The properties that science discovers are all causal and structural (for example, spatial). They are the properties represented by “the bound variables in our scientific theories.” And what science is able to tell us about them is exhausted by the laws in which they appear. For instance, what do we know about mass? We know that it confers momentum on the things that have it, as well as inertia and the acceleration of gravity. We now know that it is convertible with energy in a certain way. This more or less concludes what we know about mass. What is mass “in itself”? What is its “categorical ground”? We have no idea and will never have. Such facts, whatever they may amount to, are forever inaccessible. The same goes for electric charge, frequency, and every other scientific property.

What goes for the properties referred to by scientific theories goes for everything else we can know about the world outside our minds. We can learn of things outside our minds only by their effects on us. What has no effects we cannot learn about. But that doesn’t mean it doesn’t exist! In fact, there must be more to the world than causation and structure. It can’t be relations all the way down. Relations require relata. There ultimately have to be things in themselves to be causally and structurally related. Only we will never know what they are. There is thus a great deal of physical reality, including physical properties of objects all around us, of which we are entirely and necessarily ignorant.

This is why, in sense-perception, the relations we perceive between objects may be real, but the intrinsic properties cannot be. Causal and structural properties make a difference to events in the world, and so our sense organs can detect them. Intrinsic properties do not make a difference to events in the world, and so our sense organs cannot detect them. But there must be some intrinsic properties! And since our sensory systems cannot detect them, they must supply them. Just as reality cannot be relations all the way down, neither can our perceptions. We cannot perceive only relations. We must perceive relations between intrinsic objects. Thus, the intrinsic properties of experience exist, in Simon Blackburn’s handy phrase, to fill in space. We live in a sensory world of real structure and dynamics but of illusory intrinsic qualities.

This is the role of consciousness. Consciousness is “what it’s like” to be you and do the things you do. In the case of sense-perception, what it’s like to perceive, say the cat on the mat, consists primarily of the intrinsic qualities, such as the colors, that are attributed in perception to the cat, the mat, and so forth. Likewise, when it comes to all other mental events, such as sensations, emotions, feelings, and thoughts, what it’s like to undergo these events consists in the first instance of intrinsic qualities. Consciousness is the faculty that presents intrinsic qualities.

If this is right, then zombies are impossible. Perception requires intrinsic objects, and consciousness is the presentation of intrinsic properties. I am right to think that if I didn’t have consciousness, I would notice. (And Chalmers is right about this, too.) If I did not have consciousness, I could not have sense-perceptions. Since zombie-me has no consciousness, it cannot have sense-perceptions. Therefore, it cannot be functionally identical to me. So, there is no zombie-me.

I don’t mean to suggest that any sort of “perception” in the sense of detecting and responding to properties in the environment requires consciousness. A thermostat detects the temperature in a room in the sense that it has a state that tracks the temperature. A self-driving car likewise detects road conditions. Maybe even bat echolocation similarly lacks consciousness (although this seems unlikely). But human perception is not like this. Human perception presents intrinsic objects; this requires consciousness. Consciousness is the presentation of intrinsic objects (and consequently of relations between them).

I cannot say why human perception (and mental life generally) employs consciousness. Perhaps it has to do with intentionality, by which I mean the representation of something other than what does the representing. Your thought of your mother, perception of a tree, and memory of what you did on your last birthday are all intentional states. Notice that the thermostat doesn’t actually represent anything. It has a state that tracks (i.e., covaries with) temperature and controls a heater or air conditioner accordingly. But the state that tracks temperature is not about the temperature or anything else. (More sophisticated proposals which, however, still run along essentially similar lines, such as this one, do not solve this problem.) Of course, we may interpret it as being about the temperature. But this is a character we impute to it. In itself, it is a “blind” causal mechanism. By contrast, your perception of a tree, by itself, really is about the tree, as is your thought of your mother or of the color red. The original representation of anything requires presenting it as something distinct from what does the representing. Perhaps this requires presenting an intrinsic nature. But this of course is entirely speculative.

I also cannot say how this account of consciousness avoids the problem of the closed system of physical causation. My account does not require intrinsic properties to have causal powers. If consciousness presents intrinsic properties, then it is consciousness that exercises causal powers; the intrinsic properties may be merely the objects of conscious awareness. But their presence or absence on this scheme still makes a causal difference in the world. This means that certain actions of consciousness will vary depending on factors (intrinsic properties) that are not recognized in the book of physics.

Unlike Chalmers’s own ideas about consciousness, this doesn’t require us to introduce anything nonphysical. This is not dualism or epiphenomenalism. Intrinsic properties are physical properties, and we have independent reason to believe they exist. But they are not part of current physical science, and, other than obliquely, they never can be.

Annotated Bibliography

  • Thomas Nagel’s early article.
    • What Is It Like to Be a Bat?”, Philosophical Review, 83 (1974): 435–450.
      • This article, published just as functionalism was becoming the dominant philosophy of mind, received attention for its catchy way of showing what functionalism leaves out. However, the problem of consciousness didn’t really gain traction until the work of David Chalmers.
  • David Chalmers’s work on consciousness.
    • The Conscious Mind, Oxford U.P., 1996.
    • Self-Ascription Without Qualia: A Case Study,” Behavioral and Brain Sciences, 16 (1993): 35–36.
      • This is the earliest published writing by Chalmers on zombies that I know of. It was a comment on a target article by Alvin Goldman.
    • Facing Up to the Problem of Consciousness,” Journal of Consciousness Studies, 2 (1995): 200–219.
      • This ubiquitous article summarizes Chalmers’s view nicely, and you only have to read the first 20% to get the main argument (sec. 1–3). Unfortunately, it doesn’t talk about zombies.
    • Consciousness and Its Place in Nature,” in D. Chalmers (ed.), Philosophy of Mind: Classical and Contemporary Readings, Oxford U.P., 2002.
      • The best essay-length statement of Chalmers’s views on consciousness.
  • General article on zombies for those who want a broader view.
    • Robert Kirk, “Zombies,” The Stanford Encyclopedia of Philosophy, 2019.
  • The idea that all we can know of the world outside our minds is its structural and causal relations, not its intrinsic properties, is called structural realism. There is a large literature, but the following are noteworthy.
    • Simon Blackburn, “Filling in Space,” Analysis, 50 (1990): 62–65.
      • The best short exposition of structural realism.
    • Bertrand Russell, The Analysis of Matter, 1927.
      • The best book length treatment.

18 thoughts on “Zombies Are Impossible

  1. Surely, David, I need and want to study this essay (and your other work) much more. Thanks for sharing this adventure here. And thanks for the link in SEP.

    If a zombie-me has no phenomenal consciousness, I’d think (as Locke would, if I recall correctly) he could not know that I have such a thing or what such a thing could possibly be. Or know the entire reason I invite him to come out with me and enjoy what is now in bloom at our place. I’d think he could not know so far as I know what blue or enjoyment are. I guess that would be part of the conceptual incoherence in the notion of zombie taken to be a guy just like me, but for phenomenal consciousness, and taken to understand all my states and behaviors just so far as I understand them.

    I wonder if zombie-me should be able to see the moon illusion, or should he see it just as my camera records that moon in that moment near the horizon. And if he has lateral-inhibition neural connection in the retina, should he be able to experience the Mach-band effect when it is lain out before him and me. I’d need to dig into zombie literature anew to brush off my rustiness and figure what positions should be taken on these capacities.

    I’m not getting how we can know that none of the properties we take for intrinsic physical properties are not really intrinsic. I get that they are not intrinsic in the experiential sense, like phenomenal blueness. But how can I know that electron spin, charge, and inability to reach velocity of light are not really physically intrinsic properties? Where is there a demonstration that the spin axis of the earth is not an intrinsic property of the spinning earth? (Blackburn seems blindered on what is physics and how it works.) (In my new metaphysics in press, no existents are without situation [and I argue for that], so no sound notion of the intrinsic can mean devoid of situations; situation of an existent in space and time or in causal powers and susceptibilities or in our knowledge cannot void, out the gate, intrinsic character of the existent or the existent as known.)

    On the philosophical zombie and some of its conceptual problems is also the book The Epistemic Role of Consciousness (2019) by Declan Smithies.
    “This book is primarily concerned with conceptual questions, rather than metaphysical questions, about the significance of consciousness. My question is whether there is any conceptual, analytic, or a priori connection between the phenomenal concept of consciousness and our other psychological and epistemic concepts, including concepts of mental representation, belief, and knowledge. That is why I’m asking how much of our mental lives could be preserved in zombies. Is it conceivable—in the sense that it’s not ruled out on a priori grounds—that a zombie could have the capacity for mental representation, belief, or knowledge? / I’ll argue . . . that our psychological and epistemic capacities cannot be functionally defined in terms of their causal roles. Instead, they are defined in terms of their connections with phenomenal consciousness. On this view, it is inconceivable that zombies share our mental lives.” (9)


    • Hi Stephen. Thanks for the reference to the Smithies book. It looks interesting. But since it’s $70, I will probably not read it.

      I think zombies should indeed be subject to the moon illusion, Mach bands, and all similar phenomena. If nothing else, otherwise they would not be functionally identical with us. But also, as you say in the case of Mach bands, where we know a neurological cause, there would be no problem. (When it comes to the moon illusion, so far as I know, the jury’s still out on what exactly causes it.) Also, the zombie would have emotions and be delighted with your blooms, etc.—but in a Gilbert Ryle sort of way. For that matter, he could report that blue makes him a little sad, red angry, and so forth. But he would not have had conscious experience of red, blue, sadness, anger, or delight.

      The main problem I’m trying to indicate with the zombie story is that the zombie is supposed to have perceptions in the same way we do but without intrinsic properties; the zombie operates by physical causation only. But this can’t be right, since our perceptions do include intrinsic properties. And it doesn’t seem that intrinsic properties can have any effects without consciousness. Since intrinsic properties themselves have no effects, the only way they can exert influence is through consciousness of them. That’s why we have consciousness, and so, if zombies operate the way we do, why zombies must have consciousness too. (In other words, they aren’t actually zombies.)

      I don’t know what you mean when you ask how we can know that physical properties like spin and charge are not intrinsic properties. Charge, for example, is a property that causes, say, an electron to be deflected in electric and magnetic fields, to be attracted to a proton, and so forth. These are causal properties, not intrinsic. How we know they are not intrinsic is by definition. The question is not whether these properties could somehow after all be intrinsic, but whether in addition we have to posit some further intrinsic component. What Blackburn is arguing (concerning categorical grounds of dispositions) is that we don’t, and indeed that we can’t.

      Likewise, the axis of a spinning Earth is a relational property. It only exists in relation to the Earth. I don’t know what your ideas about space are, but even if you believe in some idea of “absolute” space, I don’t see how there can be any intrinsic element of space other than a point. Everything else in space consists in relations, doesn’t it? If so, then they are not intrinsic.

      But probably I just don’t understand what problem or query you’re raising.

      There is by the way a decent TED talk by Chalmers in which he explains his ideas about consciousness. (That is, if you can bear to watch a distinguished philosopher subject himself to the whole TED talk circus thing.) https://www.ted.com/talks/david_chalmers_how_do_you_explain_consciousness?language=en Unfortunately, he doesn’t talk about zombies in this talk.

      Liked by 1 person

  2. This isn’t really directly on topic, in the sense of querying some particular claim you make in this post, but I’m curious if you think of the position you defend here as Kantian. The thought you describe in the paragraph that begins, “There is a general lesson here worth emphasizing,” sounds (to me) like a scientifically respectable gloss on Kant’s first Critique and Prolegomenon. I’m wondering if you intended that, or see it that way.

    And no, I will not accuse you of complicity in the acts of “the most evil man in world history” if the answer is “yes.” I’m asking because I haven’t really come to terms with Kant myself, and feel the need to do so. Though I’m not entirely sold, this seems as promising a version of Kantianism as any I’ve encountered.


    • Actually, yes, I think there’s a Kant redux aspect to this. (Which is a little weird, since I’m not a fan of Kant’s “critical” philosophy, but what the hell…) But of course, there are two huge differences. First, Kant thinks we can know nothing at all about things in themselves (i.e., in the external world), whereas structural realism says it’s only the intrinsic properties of external things that we can’t know. The structure and dynamics of external things, which are what we need to survive and promote our lives, are knowable. Second, Kant thinks the problem is that our own minds impose distorting structures on our experience of anything, so that it is our own minds in the process of cognition that impose the conditions that cut us off from external reality, whereas structural realism says that certain external properties, the intrinsic ones, are by their nature inaccessible. For Kant, the problem lies with our (transcendental) cognitive processes; for structural realism, the problem is with certain external properties.

      Still, the flavor in a way is similar! Especially if you think that even space, as it intrinsically appears to us, is included in what SR counts as illusory. I mean, the structure relations (topology) of space that we perceive may be real, but beyond that? Who knows what space in itself is like!

      Liked by 1 person

      • Right. But I think the view is closer to Kantian than even your comment suggests.

        On the first point,

        First, Kant thinks we can know nothing at all about things in themselves (i.e., in the external world), whereas structural realism says it’s only the intrinsic properties of external things that we can’t know.

        If Kant is interpreted as equating “things in themselves,” not with the external world per se, but with its categorical ground in intrinsic properties, that closes the gap between his view and yours.

        On the second point,

        Second, Kant thinks the problem is that our own minds impose distorting structures on our experience of anything, so that it is our own minds in the process of cognition that impose the conditions that cut us off from external reality, whereas structural realism says that certain external properties, the intrinsic ones, are by their nature inaccessible. For Kant, the problem lies with our (transcendental) cognitive processes; for structural realism, the problem is with certain external properties.

        That sounds less like Kant in his own voice (“in itself”) than a critical commentary on Kant. Kant need not be interpreted as saying that our minds impose distorting structures, and need not think that our transcendental cognitive processes present a problem. If he’s interpreted as equating “things in themselves” with their metaphysical basis in intrinsic properties, then both you and Kant are saying that consciousness by its nature renders us incapable of knowing those intrinsic properties, but constructs a world of causal relations out of those intrinsic properties. I think that’s clear in this passage from your post, where you say (focusing particularly on the last sentence):

        This is why, in sense-perception, the relations we perceive between objects may be real, but the intrinsic properties cannot be. Causal and structural properties make a difference to events in the world, and so our sense organs can detect them. Intrinsic properties do not make a difference to events in the world, and so our sense organs cannot detect them. But there must be some intrinsic properties! And since our sensory systems cannot detect them, they must supply them (my italics).

        In saying that our sensory systems “supply them,” you’re not (necessarily) saying that our sensory systems are a source of “distortion.” It’s not obvious that Kant is, either.

        It’s been a long (long) time since we’ve had a conversation, philosophical or otherwise, but the view you’re taking bears at least some similarity to the interpretation of Kant offered by my one-time Notre Dame colleague, Eric Watkins.


        I haven’t read Eric’s stuff since grad school, but my hunch is that you might find it of interest, at least as far as the Kant connection is concerned.

        Liked by 1 person

        • Surely this is an idiosyncratic reading of Kant? One thing I would have thought is very hard to dispute is that Kant says that categories such as causation and the forms of intuition, space and time, are inapplicable to the noumenal world and unreal (so far as we can know). They are merely conditions of understanding and sensibility. They explain the possibility of synthetic a priori knowledge because they are imposed on experience by the transcendental mind. They therefore do not pertain to external reality (so far as we know), because otherwise we wouldn’t need Kant’s Copernican inversion to explain them. “We can accordingly speak of space, extended beings, and so on, only from the human standpoint.” (CPR, B42) Again, the noumenal world is just the place where we may hope that God, freedom, and immortality exist, these being denied to us by the causation-governed phenomenal world.

          This is not compatible with structural realism (as I advocate it—actually, there are a bunch of different versions), which holds that space and causation do exist, and indeed that the causal laws that we discover from experience are the very same laws that govern the external world. When we discover the structure and dynamics of the world outside our minds, we are discovering the world as it is in itself. There is no distinction between causal laws as we experience them and as they are in themselves. The distinction is between relational and intrinsic properties. Moreover, intrinsic properties are not categorical grounds of causal properties, in the sense Blackburn seems to mean. That is, they aren’t what give rise to or support causal properties. They only “fill in space.” They are no more closely related to causal properties than different causal properties (say, charge and spin) are related to each other. Again, there is no room for God or other science-violating things to exist in the external world.

          So, I don’t think structural realism is all that Kantian, unless we take a very peculiar view of Kant.

          Liked by 1 person

          • Point taken. I guess I’d say that view becomes more Kantian if one accepts Blackburn’s view that intrinsic properties are the categorical grounds of causal properties (which I think I was unreflectively taking for granted). But if you reject that, then yes, the view is Kant-flavored but not Kantian.


            • That said, this can’t be right:

              One thing I would have thought is very hard to dispute is that Kant says that categories such as causation and the forms of intuition, space and time, are inapplicable to the noumenal world and unreal (so far as we can know).

              The possibility of noumenal causation is one of the perennials of the Kant literature, maybe one of the most disputed topics in it:



              Kant’s views are themselves idiosyncratic, so the interpretations have to follow suit!


              • Interesting! These papers are paywalled, so I don’t know what these guys have to say. But I would be surprised if either of them simply says that for Kant, there is “causation” in the noumenal world of a kind we are able know anything about. I see that Henry Allison (in his book Kant’s Transcendental Idealism) devotes a chapter to the problem (of how the transcendental mind can be “affected” by noumenal things-in-themselves), and it’s faintly amusing to watch him squirm and wriggle. He delivers a verdict of innocence for Kant, of course. “[T]he function of the categories in these transcendental contexts is purely logical, and does not carry with it any assumptions about their objective reality with respect to some empirically inaccessible realm of being.” (254)

                You have said a couple of times now that Blackburn regards intrinsic properties as categorical grounds of causal properties. I really don’t read him that way. He says, “better not to insist on grounds in the first place,” and I think his view is that categorical properties are subjective, and as for the objective order, it seems to be “powers without end,” beyond which we have no idea. I am happier to say that there are intrinsic properties out there than he seems to be, because logically I think there must be. But I don’t think we have any idea of what could “ground” powers, and I guess I’m less bothered by that also. Why shouldn’t there be brute powers?


          • Kant does not think of noumena as unreal, and he does not think of forms of intuition or the categories of the understanding as distorting something. This much is not an idiosyncratic picture of Critical Kant among contemporary Kant scholars.

            Kant expressly denies that the sensory appearances from which experience is made are or even could possibly be illusions (B69–70, A293–98 B349–55, B157–58).

            There are some things he seems to think we do know about things in themselves: that they are various, have differences among them, and have ways of being.
            “Even if we could through pure understanding say something synthetically about things in themselves (which, however, is impossible), then this could still not be applied to appearances, which do not present to us things in themselves. Hence in the case of appearances I shall, in transcendental deliberation, always have to compare my concepts only under the conditions of sensibility, and thus space and time will be determinations not of things in themselves but of appearances; and what things may be in themselves I do not know—nor indeed need to know, since, after all, I can never encounter a thing otherwise than in appearance.” (A276–77 B332–33)

            I gather that David is claiming we know quite a lot more about intrinsic properties than that they are various, have differences among them, and have ways of being.


            David, it seems a cramped notion of the real to say that intrinsic properties are not real if they do not exist in the way they appear to exist. Maybe that talk of “not real” just needs cleaning, but maybe you really, really mean it. Also it seems odd for “exist” to be wider than “real.”


            A rather remarkable thing happened in connection with the Smithies book. It was published by Oxford in 2019. When I looked into it in connection with David’s project, I found that the final chapter of the book is devoted to contrasting Smithies view with “the rule of Phenomenal Conservatism” of Michael Huemer (Skepticism and the Veil of Perception, pp,103–18) and network around that rule. Smithies brings into consideration, along with Michael’s 2002 book, eight papers of Michael’s from 1998 to 2018. Here is the remarkable thing: When I gave the preceding information on Michael’s Facebook page to broadcast it to his large audience there, it turned out that Michael had not known of this book. He was grateful to learn of it. Walter and I find it rather amazing that Smithies had done so much study of Michael’s work in this area and published on it, yet, though a contemporary, had never communicated with Michael concerning it.


            • I didn’t mean to upset anybody by the word “distort.” And I have no stake in it and might just as well have said “shape.” But really, why isn’t it accurate? According to Kant, the forms of intuition and categories of the understanding cause things to be presented in experience or appearance differently than they are in themselves. That’s the point of Kant’s distinction between appearances and things-in-themselves. Therefore, the appearances are distortions. The way we experience things is not the way they really are. Otherwise we could know things as they are in themselves.

              There are some things he seems to think we do know about things in themselves: that they are various, have differences among them, and have ways of being.

              Well, since plurality, unity, reality, and existence are all categories of the understanding according to Kant, I’m not sure he can say this any more than he can say that things-in-themselves are causes of their appearances in us.

              Of course, he says all these things. But whether his doing so is consistent with his system is very doubtful. Obviously, Kant interpretation is difficult, and the further you get into the weeds, the harder it becomes. It is entirely possible that there might be a way to interpret Kant as having the right to make these claims that is based on some creative and insightful new way of reading the text. But my impression is that mostly these claims are produced by Kant boosters who are trying to square his circles for him. Certainly, that is the case with Henry Allison. As opposed to scholars like that, give me Strawson any day.

              I gather that David is claiming we know quite a lot more about intrinsic properties than that they are various, have differences among them, and have ways of being.

              We can know the intrinsic properties in which we (i.e., our sensory and other mental systems) clothe the world. We know them by acquaintance. But not the intrinsic properties that external things have. About those we know zippity-do-da.

              David, it seems a cramped notion of the real to say that intrinsic properties are not real if they do not exist in the way they appear to exist. Maybe that talk of “not real” just needs cleaning, but maybe you really, really mean it. Also it seems odd for “exist” to be wider than “real.”

              I’m not sure what part of my post this is referring to. When I say “intrinsic properties are not real,” I mean, for example, that the colors I see on the surfaces of all the objects on my desk right now aren’t really there. And bear in mind the qualification, “as far as we know.” I don’t have an argument to deny the very possibility of the colors I see being real qualities of the objects in question. I just think it would be a cosmic coincidence if they were really there, since, if they were, they would seem to have absolutely nothing to do with my seeing them there. I have no idea what the world outside my mind is intrinsically like.

              I do not mean to use “exist” and “real” to refer to anything different. I am not like Russell in The Problems of Philosophy saying that particulars “exist” but universals “subsist.” Unless I have goofed, “real” and “exist” should always have the same meaning.

              This raises a good question about the ontological status of certain intrinsic properties, if there are some that are never instantiated by any real particular but that ARE merely intentional objects of some intentional mental states. Being merely intentional objects that are never actually instantiated anywhere, they would be completely illusory. So, I guess we should say they do not exist. But, as I asked before in the reply about colors and tastes, how can they be even merely intentional objects if they have no reality whatsoever? I don’t know the answer to this question. The answer should depend on how it is that intentional mental states project properties as intentional objects. I have no problem saying that merely intentional objects need have no reality of any kind. But still, the mental state has to project them (“intend them”) somehow. For this to be possible might require that they have some reality, after all. But we’re now in the realm of the totally speculative, and I don’t think our current state of knowledge allows any answer.

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              • Concerning exist/real, I was looking at “But the intrinsic properties are not real. They do not exist at the objects in the way they appear to.” I agree with your followup; I can’t take ‘exists” or ‘real’ to be one wider than the other, from my modern perspective.

                Concerning Kant, I agree he is inconsistent, viz., he falls into using items from the Categories in talking about noumena. He has stuff in the categories that are simply pretentious as birthing in his sort of categories, and then he can’t keep them there in elaborating his own scheme. However, I don’t recall him ever writing, implying, or insinuating that phenomena are not real or that they are in any sense less real than noumena. And looking at him from an outside-Kant perspective, I rather think his phenomena (his sense, not Newton’s) are more real than his murky noumena (his sense, not his predecessors’), however well he can argue some sort of existence for the latter.

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                • And looking at him from an outside-Kant perspective, I rather think his phenomena (his sense, not Newton’s) are more real than his murky noumena

                  Lol, no argument there! There’s a reason Kant calls himself an idealist, after all.

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  3. There seem to be quite a few different senses of ‘intrinsic’ in use by various users in different contexts. I don’t think I’m getting what is the one you are using and crafting and whether it is indeed only one.

    How can a phenomenal quality at a particular occasion of it not be in some relation to consciousness? If we want to set that relation out of play, I’ll look for your sense of ‘intrinsic’, its specification, with consideration of relation to consciousness just resting in the background. (By ‘relation’, I mean as between two or more different relata, at least different prima facie.) So I’m supposing this is the of court of play of your ‘intrinsic’. Is that right?

    And relation these intrinsic items stand to mathematics is not different in kind from the sort of relation things in physical causal relations stand to mathematics? So relation to mathematics is also just background, not on the court in which this notion of intrinsic is to be delineated and put in play?

    How can a particular phenomenal color be out of relation to other phenomenal colors? That just doesn’t seem to be the phenomenal experience of them. By contrast, it seems that a phenomenal salty taste is not inherently relational to a phenomenal sour taste. I know this is complicated; taste has the unity of being experienced as inside the mouth, whereas apparently we need some more advanced learning to know that color or visual experience more generally implicates the body anywhere at all. My further question, nevertheless, is whether the sense of intrinsic is to be the very same for particular phenomenal blue as for particular phenomenal saltiness.


    • Yes, it’s a slippery thing to define “intrinsic property”. What I mean is that it does not consist in relations to anything else. The “consist in” is important. It is not that some instance of the property never has any relations to other things. That would be impossible, I think, unless there were nothing else in the universe! Come to talk about being the only thing in the universe, I sometimes think of it or try to explain it as just that: an intrinsic property is one that could characterize an object that was the only object in the universe. Another way to think of it might be that it could be the lone universal in the realm of universals.

      So, being related to consciousness does not make a patch of red a relational property after all, nor being one of two red balls on the pool table, nor being experienced in your mouth, etc. For, the existence of the patch of red does not depend on the existence of those other things.

      You bring up a very good point about the color wheel and the relational nature of colors. Orange is more similar to yellow than it is to blue, and this seems to be no accident! Rather, it is in the nature of orange, isn’t it? It is part of what orange is. I don’t deny this, but I still don’t think orange is a relational property. It seems to me that orange could exist even if there were no other colors. At least, “metaphysically,” this seems to be so. And the unitary colors of our psychological color space—red, green, blue, and yellow—being unitary, have no essential relations to each other or to other colors. Orange is a mix of yellow and red, which are themselves not mixes of anything. They are like salt and sour in that regard.

      This raises interesting questions about the metaphysical status of colors. On the one hand, the color wheel exists only because of our psychology. If we were dichromats, we would have a different color space, as tetrachromats surely do—which could be radically different from ours, for all we know. And there are other species with quite differently organized wavelength-sensitive (“cone”) receptors, whose color experience is probably completely unlike ours. Yet colors in some sense must exist, even if only as “qualia.” And I think further that, even to exist as qualia, they must have some real existence. Even if they are only mental projections, i.e., merely intentional objects of the visual system, how is that brought about if there is no reality to colors whatsoever?

      Anyway, I wonder to what extent the color wheel is an artifact of human psychology; in other words, a structure determined by us. But whether it is or not, it is a structure that pertains only to the color space itself. The colors still play no causal role in the world that I can see.

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