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A Critical Review of Thomas Nagel’s latest book Mind and Cosmos

MindandCosmoscoverThomas Nagel’s book Mind and Cosmos has garnered a lot of attention since its publication, with the reaction being intense, heated, and of largely mixed opinion (For a nice overview and response to negative views, see here). Not surprisingly, those sympathetic to naturalism have been harsh in their assessment, and those not so sympathetic have been full of praise. My assessment is ultimately negative, but I think both the defenders and critics of Nagel’s book have relied on a set of shared assumptions that are deeply problematic and masked by ambiguity. By exposing the hidden assumptions framing the debate between “reductionism” and “non-reductionism”, I show that Nagel’s criticism of “reductionism” is sound, but this is no reason to reject physicalism, only an outdated and confused version of physicalism.

1. The Problem of Hierarchy: Two Views of Reduction

The controversial subtitle of Mind and Cosmos is “Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False”. Quite the claim! But what exactly is “Materialist Neo-Darwinism” and who really holds this view? More precisely, Nagel’s target for criticism is what he calls:

“A particular naturalistic Weltanshauung that postulates a hierarchical relation among the subjects of those sciences.”

I have a lot to say about this notion of a “hiearchical relation”, so bear with me! I propose Nagel’s invocation of a “hierarchy” is ambiguous between two senses of the term. First, there is a hierarchy of scale that is compositional e.g. Society is composed of individuals, which are composed of cells, which are composed of molecules, which are composed of atoms, etc. I take compositional hierarchy to be non-controversial.

The second sense of “hierarchy” is what John Heil calls a “hierarchy of being” or “hierarchy of reality”. On this view, you have lower-level “realizer bases” out of which higher-order properties “emerge”, in the sense of “strong” emergence where the whole is non-compositionally greater than the sum of the parts (whatever that means). For example, on the hierarchical view of reality, the mind “emerges”, “arises”, or is “generated” as a higher-order property “out of” the lower realizer bases, and is said to “supervene” on that lower base. Nagel is perfectly right to think this is a mysterious process, but that’s a good reason for physicalists to reject the entire hierarchical view of reality, not give up on physicalism.

The alternative picture is that reality is flat. There is one level of reality: it’s called reality! Within that level we can find hierarchies of scale and composition, but ultimately there are not two different levels or types of “being”, one physical and the other mental, with the latter “emerging” or “arising” out of the former. Nagel seems to think that physicalism is committed to this view, but ironically the problems he locates with reductionist physicalism stem from his own dualist intuitions about the existence of “higher” levels of reality. However, an ontologically serious physicalism has no room for different “levels” of reality, and thus it is not a “problem” to try and reduce the mental “level” to the physical “level” because that view of reduction relies on the problematic notion of there being a hierarchy of reality in the first place. In his book From an Ontological Point of View, John Heil recommends that

 …[W]e abandon the notion that reality is hierarchical. We can accept levels of organization, levels of complexity, levels of description, and levels of explanation, without commitment to levels of reality in the sense embraced by many self-proclaimed anti-reductionist philosophers today.The upshot is a conception of the world and our representations of it that is ontologically,but not analytically,reductive.

Agreed! This result generalizes to the entirety of Nagel’s critique of physicalist reductionism. While Nagel is right to argue that reductionism is problematic, the entire problematic of reducing higher levels of reality to lower levels of reality is a product of the dualist worldview, not the physicalist one. It bears repeating that on the physicalist view, there is no problem of “reducing” the mental to the physical because setting the problem up like that buys into the traditional dualist framework of reality as hierarchically layered. In a nutshell, Nagel is criticizing a dualistic view of physicalism, and thus his critique of physicalism says more about how Nagel views the world than it does about how physicalists do.

To be fair, many physicalists have unwittingly bought into the same “levels of being” view that is problematic, but insist that the “reduction” of the highest levels to the lowest is tractable. I agree entirely with Nagel that this project of reduction is doomed to failure, but not for the same reason Nagel does. My problem with the project of reduction is that it sets up the problem wrong, whereas Nagel think it reveals the truth of dualism (or at least the falsity of physicalism).

Nagel claims that his book is

“…[N]ot just about acknowledging the limits of what is actually understood but of trying to recognize what can and cannot in principle be understood by certain existing methods.”

Having cleared up the ambiguity of hierarchies, we can now analyze Nagel’s conclusions about what can and cannot be understood by the physical sciences. If the project is to say it is impossible for the physical sciences to “reduce” the “mental level” to the “physical level” then I agree entirely. But not because I doubt the truth of physicalism. The mental level cannot be reduced to the physical level because the whole idea of there being different levels is a product of the traditional dualist worldview where reality is divided into base terrestrial materials and higher spiritual realms.

Thus, when Nagel criticizes the project of “materialist reductionism,” he kind of has a point, but it’s impossible to see this unless we clear up ambiguities about how physicalists can think about reductionism. I propose there are essentially two types of materialist reductionism: call them Reductionism and Eliminativism. Reductionism is the confused view we have been discussing, where it’s acknowledged at the start there are two levels of being, and the problem is to reduce the mental level to the physical level or provide psycho-physical “bridge laws” between the two levels. In contrast, Eliminativism says all that exists is the physical level. Rather than starting with two levels, Eliminativism starts with one level and all phenomena as well as explanations of phenomena are framed in terms of this level of reality.

As I see it, Nagel is right to criticize Reductionism, but his arguments don’t apply to Eliminativism. Unfortunately, Nagel doesn’t make this distinction clear and doesn’t engage with the alternative one-level view of reality, which is the true competitor to the traditional dualist worldview. I can imagine what Nagel would say if he heard about this distinction. He might say it’s completely counter-intuitive because it denies the reality of “first person subjective experience”. But again, this talk of “denying reality” is ambiguous between denying that psychological phenomena “live” in the higher-realm of a two-level reality or denying that it exists at all. Physicalists don’t have to deny that psychological phenomena exist; they will just say that, whatever they are, they “are” just like everything else: existing in the complex, flat ontology that is our physical universe. Thus, physicalists only deny the reality of mental phenomena if it is assumed that mental phenomena “live” in a higher plane of existence in the two-level picture of reality.

Of course, given the complexity of the universe, physicalists have no expectation that humans will be cognitively comfortable (or even capable) of accounting for everything they want to explain in terms of the lowest compositional scales (atoms, quarks, etc). Rather, we abstract to higher compositional scales to deal with complex phenomena like human civilization. But all this abstraction is abstracted within a single level of reality. The psychological necessity of parsing the world into higher and lower scales is not a metaphysical proof of separate planes of reality. In fact, a physicalist understanding of human cognition would predict that humans would not be capable of handling reams of data without compressing it with language, graphs, equations, simulations, models, etc.

Thus, the following statement by Nagel is actually a prediction of the naturalistic concept of human cognition:

“For a long time I have found the materialist account of how we and our fellow organisms came to exist hard to believe.”

Of course such a massively complicated proposition is “hard to believe”. A lot of things are hard to believe because we are forced to use our puny primate brains to understand a large, scarily complex physical universe with weird things like black holes, quarks, and gravity. Why would we expect it to be easy to imagine abiogenesis? Essentially, Nagel’s argument that not-P is: “I don’t understand P, therefore not-P.” But if P is physicalism, and physicalism predicts that humans will have a hard time understanding complicated things, our lack of understanding (especially of nonscientists) is surely not a refutation of physicalism, merely a recognition of its cognitive complexity.

2. Flubbing the Facts

Ontology aside, I do think Nagel makes some empirical gaffes exposing his ignorance of mainstream biological science, especially when discussing the state-of-the-art materialist conception of abiogenesis. He says, incredibly:

“The more details we learn about the chemical basis of life and the intricacy of the genetic code, the more unbelievable the standard historical account becomes”

If history has taught us anything, believability by non-scientists is not a good metric for the truth of scientific claims. For many non-scientists, Einsten’s theory of relativity is unbelievable, but that obviously has no bearing on its truth. Nagel continues:

“[Abiogenesis] flies in the face of common sense…

“….It is prima facie highly implausible that life as we know it is the result of a sequence of physical accidents together with the mechanism of natural selection

“…When we go back far enough, to the origin of life – of self-replicating systems capable of supporting evolution by natural selection- those actually engaged in research in the subject recognize that they are very far from even formulating a viable explanatory hypothesis of the traditional materialist kind”

It would behoove Nagel to google the phrase “hydrothermal origins of life” to find proposed models of abiogenesis that start from recent discoveries of deep-sea heat vents. A quick search on Wikipedia and you can find the “iron-sulfur world theory” of abiogenesis. There are probably other rival hydrothermal theories, and I have no idea whether any of them are true, but the point is that they seem, to me, like a “viable explanatory hypothesis of the traditional materialist kind”.

Perhaps there is an ambiguity in Nagel’s use of “formulation”. Maybe he means “nobody has formulated a complete explanation established to be almost certainly true”. This would be true, but that’s simply an argument from ignorance. You can’t infer from the fact that we haven’t yet formulated a “complete” explanation that there isn’t a complete explanation.

However, if Nagel means “nobody has even formulated a viable educated guess” about the origins of life, this is almost certainly false, unless he can show why hydrothermal models aren’t “viable” as possible explanations.

3. Good Darwinians vs Bad Darwinians

Another thing that confused me is who Nagel considers to be a “bad Darwinian materialist” and who is a “good” materialist. Right after harshly criticizing Richard Dawkins for explaining the evolution of the eye “merely as a result of chemical accident, without the operation of some other factors determining and restricting the forms of genetic variation”, Nagel gives an example in a footnote of presumably “good”, non-reductionist Darwinians, “who insist that the evidence calls for a more restricted account of the sources of variation in the genetic material.” Surprisingly, Nagel cites Stuart Kauffman has a “good” non-reductionist, saying in that same footnote “Stuart Kauffman suggests in several books that variation is not due to chance, and that principles of spontaneous self-organization play a more important role than natural selection in evolutionary history.”

This is confusing on multiple levels. Is Nagel implying that Kauffman is “on his side” merely because he denies that all variation is due to chance alone and not chance in addition to other factors like the material property of spontaneous self-organization? If big, bad “Darwinian materialism” is supposed to be the claim that chance alone is the full story, then Nagel is making a stink about a view that few biologists actually hold. It might be convenient to treat chance has the primary operator, but this is because dealing with the entire material evolution of cellular matter is absurdly complicated, and would require a ridiculous amount of computing power to simulate.

I can’t speak for Kauffman’s own ontological views, but Kauffman-esque “non-reductionism” is ambiguous between materialist Reductionism and materialist Eliminativism. It’s conceptually possible that all the “spontaneous” self-organization of matter is a property of the single level of reality that is the physical universe. This might be wildly complex, but why shouldn’t it be? It’s the universe itself we’re talking about here, not a toy model of it. But nothing about wild and strange self-organizing properties of matter is inconsistent with materialist Eliminativism. Thus, Nagel’s appeal to Kauffman has a counter-example to reductionism is ineffective as a genuine criticism of the physicalist worldview.


As a card-carrying “Darwinian materialist” who wears his naturalistic credentials proudly, I am sympathetic to the received criticisms of Nagel’s book. However, unlike other naturalists who have criticized Nagel’s book, I think Nagel’s criticism of Reductionism is sound: it is impossible to reduce the mental level to the physical level. Nagel’s critics have mistakenly limited their options to either joining Nagel in attacking Reductionism or accepting Reductionism as formulated by Nagel.

I reject both options in favor of Eliminativism. The reason why it’s impossible to reduce the mental level to the physical level is that this very way of setting up the problem belies the traditional view of reality as composed of “levels of being”, with the mental level “emerging out of” or “arising from” the physical level. For eliminativists, there is a single level: physical reality, and humans exist only on this level. But we certainly don’t talk or write this way. For good reason: we have puny primate brains with finite memory and processing power. It’d be futile to try to understand WWII in terms of Schroedinger’s equation, but this cognitive inability does not entail the falsity of quantum mechanics. Likewise with psychology.


Filed under Books, Consciousness, Philosophy, Psychology

Some thoughts on the conceptual coherence of "philosophical zombies"

The Zombie argument has always rubbed me the wrong way. This post will attempt to explain why. Let me first try and reconstruct the argument in my own words, with the intention of being fair to Chalmers’ underlying intuitions about consciousness.

For Chalmers, consciousness is the “what it is like” of an agent. He claims that he can only know for sure that he is conscious, that there is “something it is like” to be him. For every other conscious being, Chalmers thinks he can only infer that they are based on third-person evidence, as opposed to having self-evident first-person knowledge of qualia states, the “qualitative” or “subjective” phenomena of having a perspective on the world, having a “phenomenal” world, etc. Chalmers thinks this phenomena of “phenomenal consciousness” is really strange philosophically. It is the source of the famous mind-body problem, the basic idea that there are two general aspects known in experience, mental phenomena and physical phenomena. Mental phenomena are “things” like sensations, perceptions, beliefs, desires, imaginations, feelings, pains, and thoughts. For Chalmers it is important to distinguish two ways of understanding these mental phenomena. The first way is in terms of their roles in a causal-functional economy, of how they “do stuff” that is useful. This is what Chalmers calls “access consciousness”. It is “easy” to explain access consciousness neurologically, because we can make sense of functions in terms of causes, and we know how neurons cause things to happen in the brain and body. The second way of understanding the mental phenomena is in terms of how there is a qualitative “something it is like” to be the subject of those sensations, beliefs, pains, etc.  This is what Chalmers calls “phenomenal consciousness”. It is “hard” to explain psychologically in terms of functions or adaptive usefulness.

This is the central claim for Chalmers: he claims to not be able to conceive of any functional usefulness for this phenomenal consciousness. Imagine an atom-for-atom duplicate of your body in an alternate world. Chalmers thinks that he can coherently conceive of this duplicate as a “Zombie”, that is, a being who lacks phenomenal consciousness. If you prick a Zombie, he will yelp and move his arm back. If you asked him if it hurt, he could produce verbal behavior that describes in great detail what it is like to feel pain. He could even write philosophical essays about the distinction between phenomenal and access consciousness, and wax poetic about the great joy of sensing and experiencing the world from a first person perspective. But the Zombie would not be conscious, in any way, even though it shared exactly the same set of 100 billion neurons, all arranged in the same same chemical soup and organized in the exact same way. Imagine hooking up a conscious human and his Zombie to a brain scanner, and asking the conscious subject to report when he starts to mind-wander and ruminate to himself, about either the past, present, or future. The scanner for the Zombie would look exactly the same, of course. And if you asked the Zombie to report any mind-wandering or self-conscious thinking, his report of the time of the conscious thought would be exactly the same as the conscious subject. In fact, if the conscious subject and the Zombie were physically identical, you could mix them up in the lab room and there would be, in principle, no way of telling one from the other.

This lack of coherent criteria for telling a Zombie from a conscious subject  in a real life setting should set off huge philosophical warning bells. Chalmers’ basic argument seems to be that since he cannot imagine any possible way of telling a functional story about the “qualitative” or “first person” perspective, and thus about consciousness, it is necessary that physicalism is not true, since physicalism claims that mental phenomena are really just physical phenomena. Chalmers is a monist, but he thinks that “conscious” things (i.e. qualitative properties), exist in a fundamentally different way than physical things like the brain. Hence Chalmers is an old-fashioned dualist wrapped up in modern garb. He thinks that physical matter gives rise to two types of properties: physical properties and mental properties. And since these two properties have to be explained in fundamentally different ways, physicalism (the idea that only “physical, causal-functional stories” suffice to explain mental phenomena) is necessarily false.

I think the problem here is as follows. Chalmers leads us astray from the start when he articulates what needs explaining and what is philosophically interesting. For Chalmers, what is philosophically interesting is first-person experience, “what it is likeness”. But this concept is never sufficiently defined or explained. He says something to the effect of “If you got to ask what it is, you aint never going to know.” This, of course, doesn’t satisfy me at all. First, I want to know just what this first-person experience is. What concept of person are we working under? Is a coma patient a subject of experience? Why not? It seems perfectly conceivable that there is “something it is like” to be a coma patient insofar as she is “living” in the world and interacting with it according to the individual idiosyncrasies of her still vegetatively working brain. Surely, on pains of conceptual parsimony, the coma patient’s unconscious mind has privileged, first-person access to the mental content that is the unconscious mental phenomena such as the processing and manipulation of information streaming in from the total environmental envelope, even if on a dim and vegetative scale. It makes perfect sense to say that the coma patient’s brain is most assuredly processing auditory data unconsciously, and this  constitutes an instance of a mental phenomena, under almost every modern definition of mental phenomena. And since mental phenomena are defined by Chalmers as having a qualitative component, then, on pains of contradiction, we are forced to conclude that “there is something it is like to be unconscious”.

And if this is the case, then the conceptual usefulness of defining what needs explaining about minds purely in terms of phenomenal consciousness looks doubtful, for the problem is this: We all know intuitively that there is a huge “mental” difference between a coma patient and a fully awake, linguistically competent human. Yet in terms of Chalmers very conceptual framework, there is not a fundamental constitutive difference in phenomenal consciousness between the coma patient and the adult human, only a difference in degree of “phenomenal dimness”. If you doubt this, ask yourself this: what is the difference in epistemic access to the mind of a bat or the mind of an unconscious coma patient? If we are allowed to posit that there is “something it is like” to be a bat even when we cannot ask it if it is conscious, then why are we not allowed to posit that there is “something it is like” to be a coma patient? In both cases, you cannot ask the agent if they are conscious. We can either claim that the criterion of consciousness is reportability, or we are stuck wondering whether the bat or the coma patient is conscious. But rather than claiming the bat is probably conscious and we just can’t know it for sure, I think we should claim that the bat is not conscious simply because it doesn’t have the cognitive acumen to be meta-conscious of its first-order awareness in such a way as to be able to report on those states, either internally in thought or externally in verbal behavior.

So what is the fundamental difference between the coma patient and adult human? I claim that it is the difference between nonconscious reactivity and the operation of consciousness proper. Phenomenal consciousness as a concept is less interesting to me precisely because it isn’t useful for distinguishing humans from nonhuman animals, nor infants and coma patients from linguistically competent and verbally/intentionally responsive mentalities. And as a researcher of the mind, I think the differences between humans and nonhumans are far more psychologically and philosophically interesting than the similarities.

For starters, humans are a literate species, and one immersed in language, symbols, culture, ritual, and artificial constructions to a degree off the charts in comparison to nonhuman animals. This has huge effects on the development of the brain and the potentiality for new forms of narratological subjectivity. Moreover, the long period of time before sexual maturation in humans allows for a greater plasticity and capacity for adopting to changing environments than any other animal. And it is not the volume of frontal matter that distinguishes us from apes when body size is controlled for; it is connective fibers, the neural tissue most open to effects of plasticity.There is “something it is like” to be transported into an imaginary world while reading a book. I would be greatly surprised if any nonhuman animal was capable of experiencing such forms of subjectivity. Chalmers greatly under estimates the qualitative differences between brains competent in language and those restricted only to nonverbal mentalities (with verbal cognition referring to at least some natural capacity for understanding symbolic signs). There is also something it is like to “talk to oneself”, to tell oneself what to do, to initiate action through the slow deliberation of “inner speech”. These inner speech mechanisms are directly tied into our autobiographical memory, and help constitute our sense of conscious identity, our explicit knowledge about who we are, where we came from, what we believe, what we desire, what it is like to be us. Paraphrasing Julian Jaynes, you cannot be conscious of what you are not conscious of. For if you could not remember that you were conscious at time T, in what sense could you ever consciously know that you were conscious at time T? There is a fundamental link between autobiographical memory, capacity to self-report, and consciousness that cannot be explained in terms of Chalmers distinction between “easy problems” and “hard problems”.

This is the only way to make sense of philosophers like Robert Brandom or Dan Dennett who claim that consciousness constitutively depends on the capacity for report and be meta-aware that you are conscious. In a very real sense, what we all intuitively understand to be philosophically interesting, that which separates conscious adults from coma patients, fetuses, and birds, is not the very capacity to experience the world from a first-person view, since even coma patients are still persons in an absolutely minimal sense of bodily self-consciousness. No, what’s philosophically interesting is not awareness of the environment — something shared with earthworms, as Darwin demonstrated — but awareness of your awareness of the environment, in terms of inferentially linked concepts like “sensation”, “belief”, “desire” “meta-awareness”, “representation”, “perception”, “memory”, “thinking”, “I”, “me”, “mine”, “Soul”, “mind”, “consciousness”.

As it turns out then, consciousness depends on the concept of consciousness being active within the mental economy of the conscious subject. We thus can distinguish between nonconscious first-person subjectivity shared by all organisms and conscious first-person subjectivity dependent on the capacity to be meta-aware that you are aware, and capable of reporting on past instances of awareness in terms of narratologically structured and inferentially linked concepts learned in through childhood through exposure to intersubjective linguistic stimulation.


Filed under Consciousness, Philosophy, Psychology