Presented by Zia H Shah MD

Abstract

Metaphysical naturalism (physicalism) – the view that reality is exhaustively physical – has dominated contemporary philosophy of mind. In this essay, I argue that this paradigm is incomplete as an account of reality, especially because it struggles to accommodate the full richness of human consciousness. The hard problem of consciousness – explaining why subjective experience (“what it is like”) exists at all – highlights an explanatory gap in physicalist frameworksconsc.netiep.utm.edu. First-person, qualitative phenomena (qualia), intentionality (aboutness), and self-awareness resist neat translation into objective physical terms. Major critiques from dualism, panpsychism, and non-reductive physicalism will be examined: each offers reasons why purely naturalistic explanations fall short. We will review arguments by Chalmers, Nagel, Searle, Strawson and others showing that consciousness has features (immediacy, irreducibility, intrinsic subjectivity) that seem fundamentally at odds with a simplistic materialist ontologyconsc.netweb.mit.edu. Contemporary debates (philosophical zombies, knowledge arguments, integrated information theory, etc.) reveal vigorous dialogue but no consensus on fully naturalistic solutions. Defenders of naturalism (Dennett, Churchland, Frankish, etc.) respond with eliminativist or reductive strategies, but these often ignore the first-person perspective or side-step the core mysteriesplato.stanford.eduiep.utm.edu. In conclusion, this essay shows that naturalism requires serious augmentation or revision if it is to explain consciousness and related phenomena.

Metaphysical Naturalism and Its Commitments

Physicalism (metaphysical naturalism) is the thesis that everything is, at bottom, physicalplato.stanford.edu. It insists that all entities and properties – even mental states – either are physical or are grounded in physical reality. On this view, the “natural world” is essentially the physical world: any scientific facts about matter, energy, space and time should, in principle, account for everything. As one characterization puts it, “the nature of the actual world … conforms to a certain condition, the condition of being physical”plato.stanford.edu. Naturalists do not deny that humans have experiences, thoughts, and emotions; rather, they claim these can eventually be explained in physical terms (e.g. brain processes, information flows, neurobiology, etc.).

However, many philosophers note a tension at the heart of metaphysical naturalism: consciousness seems to “fit uneasily” into an all-physical ontologyconsc.net. Chalmers observes that while science can locate physical correlates of experience, it remains puzzling how subjective experience arises from those correlationsconsc.net. For instance, we might fully describe a brain state down to atoms and neurons, yet still legitimately ask “Why is it conscious?”iep.utm.edu. Naturalism tends to approach consciousness via objective measures (neural activation patterns, cognitive functions), but critics point out that subjective awareness is not so easily captured. The rest of this essay will explore why phenomena like qualia, intentionality, and first-person experience suggest that metaphysical naturalism, at least in its standard reductive form, is insufficient.

The Hard Problem of Consciousness

A central motivation for doubting naturalism’s completeness is the hard problem of consciousness, a term coined by Chalmersconsc.net. The hard problem asks: Why and how do physical processes in a brain give rise to subjective experience? Chalmers defines this problem as distinct from the “easy” problems of explaining cognitive functions: even if we explain every behavior and neural mechanism of perception, memory, and reporting, the question “why is this accompanied by an inner feeling?” remainsiep.utm.edu. In the words of the IEP:

“The hard problem of consciousness is to explain why any physical state is conscious rather than nonconscious… it is the problem of explaining why there is ‘something it is like’ for a subject in conscious experience…”iep.utm.edu.

Natural science excels at mapping functions and structures, but critics claim it lacks resources to account for qualitative experience itself. We can, for example, explain vision in terms of retinal cells and visual cortex activity, but it is unclear why or how the perception of “redness” ever appears to someoneiep.utm.educonsc.net. Even granting that brain processes correlate with seeing red, the question “why is this physical process accompanied by the raw feel of red?” suggests an explanatory gapiep.utm.educonsc.net.

Chalmers argues that any reductive physicalist explanation – one that tries to derive qualia from physical facts – will leave an unsolved question. He distinguishes the phenomenal notion of “what it’s like” to experience something (qualia) from mere functional or behavioral descriptionsconsc.netiep.utm.edu. One way he illustrates the gap is via conceivability: we can conceive of a creature that is a perfect physical duplicate of us but lacks any subjective experience (a “philosophical zombie”). If such a scenario is coherent, it shows consciousness is not logically entailed by the physical structureen.wikipedia.org. Chalmers concludes that consciousness may be a fundamental property of the universe, requiring new “psychophysical laws” beyond standard physicsen.wikipedia.orgen.wikipedia.org.

Critics of the hard problem (e.g. Daniel Dennett) sometimes deny that a real “explanatory gap” exists. Dennett famously quips that “there are no qualia” – he denies that consciousness contains any ineffable or intrinsic properties beyond what can be physically modeled. However, even Dennett admits that subjective reports of experience demand explanation. Many philosophers find Dennett’s dismissal unsatisfying, as it seems to undercut the phenomenological evidence for experience. The persistence of the hard problem in contemporary discussions suggests that the challenge it poses for naturalism remains unresolvediep.utm.educonsc.net.

Qualia and First-Person Experience

Closely related to the hard problem are the notions of qualia and the first-person perspective. Qualia are the qualitative, ineffable features of experience – the redness of red, the painfulness of a stubbed toe, the taste of coffeeconsc.netiep.utm.edu. These seem to have an inherent subjectivity: there is “something it is like” for a subject to have them, as Nagel famously put it (there is “something that it is like to be a bat”philosophy.uconn.edu). A naturalist picture of the brain in purely third-person terms struggles to capture this internal “how it feels” aspect.

For example, if someone has never seen the color red (say a congenitally blind person), no description of wavelength or brain activation seems adequate to convey the raw feel of seeing rediep.utm.edu. As the IEP notes, “conscious experience reveals sensory qualities… that seem to defy informative description”iep.utm.edu. This ineffability means that no purely physical description could, in principle, fully capture the qualitative content of experience. In other words, qualia are private in a way physical events are not – I cannot directly transfer my reddish qualia to another by any amount of external description or measurementiep.utm.edu.

Another feature of first-person experience is immediacy or subjective certainty. When I look at an apple, I do not infer “my brain has a red-representational state” from evidence; I simply have the experience of red. We seem incorrigibly sure about our own qualia: one cannot be wrong about how things seem (short of radical introspective illusion)iep.utm.edu. This immediacy “creates the impression that there is no way we could be wrong about the content of our conscious states”iep.utm.edu. Yet if we accept that these introspected qualities are inexplicable to an outsider, then by their own nature they resist reduction to objective factsiep.utm.eduiep.utm.edu.

Intentionality – the “aboutness” or directedness of mental states – is another thorny issue. Mental states (beliefs, desires, thoughts) refer to objects or states of affairs in a way that physical processes do not. Brentano argued that intentionality is “the mark of the mental”: all and only mental phenomena have this aboutnessweb.mit.edu. For example, your belief “cats are mammals” is about cats; your pain is about a bodily harm. No rock or storm has anything like this intentional reference. On a strict physicalist view, however, everything must ultimately be physical. How, then, do we account for the fact that brains represent the world? Searle similarly points out that syntax (mere physical symbol manipulation) cannot by itself produce semanticsplato.stanford.edu. The Chinese Room argument famously illustrates this: a computer can follow formal rules on symbols (syntax) without ever meaning or understanding (semantics)plato.stanford.edu. Searle concludes that a computer running a program is not sufficient for intentionality; the mind’s “aboutness” seems inherently bound up with conscious, semantic contentplato.stanford.edu. This challenge suggests that any purely physical or functional model of mind must explain how semantics could emerge from syntax – a move some find implausible.

Philosophical Qualia Arguments: Knowledge and Conceivability

A variety of thought experiments have been proposed to show that physicalism cannot capture qualia. The Knowledge Argument (Jackson 1982) is one of the most famous. Imagine Mary, a neuroscientist who knows every physical fact about color vision but has lived her life in a black-and-white room. When she finally sees a red apple, she learns something new – what it feels like to see red – despite her complete physical knowledgeplato.stanford.edu. From this it follows that there are non-physical facts (the facts about qualia) that were not captured by her physical description. The Stanford Encyclopedia summarizes:

“The knowledge argument aims to establish that conscious experience involves non-physical properties… [Mary] might yet lack knowledge about how it feels to have the experiences of that being. It is one of the most discussed arguments against physicalism.”plato.stanford.edu.

Critics of this argument (physicalists) reply that Mary may gain an ability or acquaintance without new propositional fact, or that knowing “all the physical facts” is incoherent unless experience facts are already physical facts. Yet even setting aside the technical debates, such intuitions reinforce that consciousness, as immediately present knowledge, appears to outrun mere third-person information.

Closely related is the zombie/inverted spectrum argument. Chalmers notes that one can conceive of a being that is physically and behaviorally identical to you but lacks all subjective experience. If such a “philosophical zombie” is logically possible, then consciousness is not entailed by physical organizationen.wikipedia.org. This implies qualia (the subjective qualities) are further facts beyond the physical descriptionen.wikipedia.org. Similarly, we can imagine two people who see colors swapped (inverted qualia) yet behave the same. If behavior and brain states do not necessitate which qualia accompany them, then qualia appear independent of the physical processesiep.utm.edu. Chalmers uses these conceivability arguments to argue that consciousness must be treated as fundamental or at least sui generisen.wikipedia.org.

Dualism: Mind and Body as Distinct

One broad class of critiques of naturalism is dualism. Classical Cartesian dualism holds that mind and body are two fundamentally different substances: the mind is an immaterial thinking thing, and the body (brain) is a material extended thingplato.stanford.edu. Descartes himself famously argued that the essence of mind is thought, while the essence of body is spatial extension; hence they must be distinct kinds of substanceplato.stanford.edu. In modern debates, some dualists reject such rigid substance-dualism but still maintain a separation. Chalmers calls his view “naturalistic dualism”: he accepts that mental states supervene on physical brain states in a lawful way, but insists the mental cannot be reduced to the physicalen.wikipedia.org. In his words, mental states are ontologically distinct from and not reducible to physical systemsen.wikipedia.org.

Dualist arguments often point to the features discussed above. For example, Nagel argues that subjective experience cannot be captured by the objective methods of physical science. His classic paper “What is it like to be a bat?” emphasizes that the subjective character of experience is inherently inaccessible from an external viewpointphilosophy.uconn.eduiep.utm.edu. When we describe a bat’s sonar system scientifically, we miss the what-it-is-like part. Nagel concludes that a purely physicalist understanding of the mind “is not easy to see”consc.net. In Mind and Cosmos (2012), Nagel goes further and contends that the materialist view has “failed to provide adequate explanations for mind”ndpr.nd.edu. He does not invoke God, but suggests that some non-reductive teleological principle may be needed to explain the emergence of consciousness.

Another dualist-like approach is property dualism: the view that there is only one substance (physical), but it has both physical and irreducible mental properties. Under this view, mental properties (like phenomenal experience) are not identical to any physical property. Searle could be read as close to this: he calls consciousness a real higher-level feature of the brain that is “causally reducible” but not “ontologically reducible”en.wikipedia.org. Thus even if every brain state causes consciousness, the conscious aspect itself is not explained away. Similarly, philosophers like Frank Jackson (before he changed his mind) used property dualism to capture the Knowledge Argument conclusion: physical facts + subjective facts. In this sense, property dualism acknowledges that the naturalist ontology (no nonphysical substance) may still need to augment physics with new fundamental properties (qualia).

Dualist critics often highlight the inadequacy of reductionism: the idea that the mental must be completely explained in terms of microphysical facts. Nagel equates materialism with reductive physicalism and insists that science’s very success suggests it can accommodate mind, yet “for Nagel, if science can’t come up with a theory of everything, it has in some deep sense failed”ndpr.nd.edu. Critics argue that physicalism might be modified to be less strictly reductive, but the point is clear: consciousness has led even staunch atheists (like Nagel and Chalmers) to consider dualistic views.

Panpsychism and Realistic Monism

If dualism feels too radical, another alternative is panpsychism. Panpsychism is the view that some form of experience or mental-like property is ubiquitous in nature, even at the level of fundamental particles. This approach attempts to “demote” consciousness from a rare emergent to something built into the fabric of the world. One motivation (advocated by Strawson, Goff, and others) is this: if physics is complete, then since consciousness exists, the basic constituents of physics must themselves have proto-conscious qualities. Strawson argues that “real physicalism” – the view that experience is truly physical – essentially entails panpsychism if we reject the possibility of consciousness emerging from the non-experientialconsc.net. He writes:

“So now I can say that physicalism, i.e. real physicalism, entails panexperientialism or panpsychism, given the impossibility of ‘radical’ emergence.”consc.net.

In other words, if one insists that the fundamental level is “all physical stuff,” and if one believes (as Strawson does) that there is no way for consciousness to emerge from nothing, then every “physical ultimate” must have some experiential aspect. If atoms and quanta had zero experience, consciousness would never appear; hence perhaps they have tiny bits of awareness that combine to form our minds. Strawson bluntly calls this conclusion “crazy” at first, but concludes that no alternative short of resurrecting dualism remainsconsc.netconsc.net.

Panpsychism is controversial, but it directly addresses the naturalist’s dilemma: either deny that consciousness is fundamental (which feels denialist) or accept that nature includes consciousness at the base level. It aligns somewhat with monist philosophies (idealism or neutral monism), but without abandoning an objective world. Contemporary panpsychists (e.g. Galen Strawson, Philip Goff) argue that their position preserves naturalism in a broad sense (nothing supernatural), while avoiding the explanatory gap by positing that experience is as fundamental as mass or charge. Critics say panpsychism is mysterious (“how do micro-experiences combine to macro-experiences?”) and violates Occam’s razor. Advocates reply that it at least treats consciousness not as a left-out add-on, but as woven into the natural order.

Non-Reductive Physicalism and Emergence

Another strategy is non-reductive physicalism: admit that mental phenomena are ultimately grounded in the physical, but insist that they are not reducible to physical descriptions. This is what Searle calls “biological naturalism.” Searle emphasizes that all mental states are caused by neurobiological processes, yet they are higher-level features of those processesen.wikipedia.org. He denies Cartesian dualism and rejects any non-physical substanceen.wikipedia.org, but insists that consciousness is a real, emergent feature of the brain. He puts it this way: the brain’s micro-events cause consciousness, and changes at the macro-level are the conscious stateen.wikipedia.org.

Importantly, Searle argues that while consciousness arises from the brain, it is not ontologically reducible to iten.wikipedia.org. He says consciousness is “causally reducible” (brain causes mind) but not ontologically reducible (consciousness is not nothing but brain chemistry)en.wikipedia.org. Thus, in principle, physics alone cannot predict or enumerate consciousness; one would have to do the actual neurobiology. Searle uses this to block claims that computers (merely running formal programs) could possess mindsplato.stanford.edu. His view preserves a broadly physicalist ontology but concedes that our scientific explanations need to expand to accommodate new emergent properties.

Other non-reductive physicalists invoke emergentism more generally: complex systems (brains) exhibit properties (minds) that are not apparent in their parts. Such properties “supervene” on the physical (i.e. no change in consciousness without change in brain), but they cannot be deduced from fundamental physics alone. In debates, some argue (like Searle) that mental properties are indeed bona fide parts of the world, even if they do not reduce neatly to neuronal firings. Critics counter that merely labeling consciousness “emergent” without detailing the mechanism is unsatisfying. Nonetheless, non-reductive approaches highlight that physicalist paradigms have in recent philosophy tended to allow for irreducible higher-level features, partly to avoid outright dualism. Even Dennett and Churchland, who are physicalists, often phrase consciousness in functionalist terms rather than identify it with a specific brain property; this reflects an implicit non-reductive stance (consciousness as function, rather than consciousness equals some neuron).

Scientific Perspectives on Consciousness

We should also consider where neuroscience and cognitive science fit in. Contemporary empirical research (neural correlates of consciousness, global workspace theory, integrated information theory, etc.) seeks to bridge the gap between brain processes and experience. For example, neuroscientist Christof Koch and Giulio Tononi’s Integrated Information Theory (IIT) quantifies consciousness by a system’s integrated information (Φ). Many physicalist scientists hope that such quantitative theories will eventually tie subjective awareness to measurable physical substrates. Other models (Baars’ Global Workspace, Dehaene’s NCC framework) focus on how information is broadcast in the brain.

However, critics caution that even sophisticated neuroscience focuses on “easy problems”. Correlating brain patterns with reports does not in itself explain why those patterns are felt experiencesconsc.netiep.utm.edu. Several scientists (and philosophers) admit that current theories address cognitive functions but do not dissolve the “what-it-is-like” aspect. For instance, Tononi’s IIT has been praised for its ambition, but some philosophers note it still requires an unexplained postulate that Φ relates to feelingiep.utm.edu. In effect, scientific frameworks can rigorously describe functions of consciousness, yet the “explanatory gap” remains unclosed: explaining behaviorally-described awareness is not the same as explaining the raw feeliep.utm.eduiep.utm.edu.

Counterarguments from Naturalism

Defenders of metaphysical naturalism have several rejoinders. Some, like Dennett or Paul Churchland, argue that consciousness is an illusion or a misunderstanding. Dennett’s famous strategy (the “Multiple Drafts” model, “Quining Qualia”) attempts to show that once we understand brain functions fully, the idea of ineffable qualia dissolvesplato.stanford.eduiep.utm.edu. In Dennett’s view, our intuitive claims about infallible inner experience are suspect; once we admit that consciousness is just another biological process, many mysteries vanish. He famously suggests that there may indeed be “no such thing as phenomenology” beyond well-described cognitive states (a claim Strawson criticizes)consc.net.

Others concede that consciousness is real but insist it must be physical; they argue that apparent anti-physicalist arguments rely on conceptual confusions. For example, some philosophers respond to the Knowledge Argument by questioning the notion of “knowing all physical facts” – perhaps Mary actually did know “what it is like” under a disguised physical description. They argue that conceivability does not entail metaphysical possibility: zombies might seem conceivable, but it could be that physical duplicates must entail consciousness (conceiving otherwise might be mistaken). Some turn to eliminativism, claiming our folk concepts of mind might simply be false. For instance, Dennett and Daniel Wegner have suggested that our introspections mislead us about free will and qualia.

Functionalist naturalists argue that once we specify the right functional roles, consciousness will be fully accounted for. They point to progress in AI and cognitive science, suggesting that the brain is just a complex information-processing machine. If a system exhibits the right input-output behavior and internal feedback loops, it should be conscious in their view. This is the reasoning behind ambitious projects like replication or simulation of the brain: if consciousness supervenes on function, then an isomorphic machine should have it tooen.wikipedia.org. Moreover, some adopt eliminative materialism about qualia: that the notion of qualia is a folk-psychological error. If so, then “explaining consciousness” just means explaining complex functions (behavior, self-report, learning), leaving no mystery in the end.

Why Naturalist Counters May Be Insufficient

While naturalist positions are in principle possible, critics argue they often evade the core questions. Eliminativism (denying qualia) is deeply counterintuitive – it would imply that what seems most immediate and certain (our own experience) is an illusion of languageiep.utm.educonsc.net. Many find it epistemically dubious to dismiss first-person evidence when science has no better account. Denying qualia may solve the philosophy puzzle but at the cost of denying the obvious.

Reductionist functionalism, meanwhile, can explain behavior but struggles with subjectivity. Even if a robot passed the Turing Test, the Chinese Room argument suggests it could behave appropriately without understanding. Searle’s critique holds for any computational model: syntax is not enough for semanticsplato.stanford.edu. Some contemporary philosophers argue that neural networks and statistical models may similarly lack true consciousness despite impressive performance; our ability to attribute experience to ourselves might not extend to silicon.

The conceivability arguments remain a thorn for physicalists. Adversaries insist conceivability is misleading or that imagination is flawed, but the fact that we feel free to conceive of inverted qualia or zombies indicates the intuitive separability of mind and matter. Even if one allows that conceivability is not a proof of possibility, it underscores how far apart our concepts of physical processes and conscious experience seem. If integrated information, say, could someday be measured by Φ, critics would ask: why is high Φ felt as anything at all? Without an account of this, the hard problem shifts rather than vanishesiep.utm.eduiep.utm.edu.

Finally, appeals to science presupposing that consciousness will eventually be explained physically assume a kind of confidence (belief in eventual closure) that some find unwarranted. Chalmers warns that science might always leave a remainder of “further facts” about experienceen.wikipedia.org. Nagel similarly suggests that the very possibility of complete reduction is unlikely: if mind and value are essential parts of our world, then a purely “materialist neo-Darwinian” framework will systematically fail to explain themndpr.nd.edu.

Epilogue: Beyond Naturalism?

In sum, the debate over consciousness reveals that metaphysical naturalism, while powerful and fruitful, is arguably incomplete. Human consciousness exhibits features – qualitative feel, irreducibility, intentionality and immediacy – that do not easily align with a paradigm centered on microphysical description. This does not mean naturalism must be abandoned; rather, it may have to be enriched or revised. Possibilities include recognizing consciousness as a fundamental aspect of nature (in the spirit of Chalmers’s “naturalistic dualism” or Strawson’s panpsychism), or developing new scientific principles that tie physical and phenomenal domains. The history of science teaches us that paradigms evolve: just as physics once expanded to include electromagnetic fields and curved spacetime, the philosophy of mind may need to expand beyond classical physicalism to fully account for reality.

The conversation between naturalists and their critics is ongoing. Naturalists have not capitulated: they challenge every assumption and press for empirical grounding. Critics urge humility, warning that the “successes” of science do not guarantee a complete metaphysics. Perhaps the final lesson is that consciousness demands a pluralistic humility. It may be a phenomenon that transcends any one framework – a window on a deeper order. As John Dupré observes of Nagel’s project, the very reluctance to appeal to supernatural explanations suggests a quest for natural principles that are richer than materialist orthodoxyndpr.nd.edu. Whether the answer lies in dual aspects, panpsychic fundamentality, or as-yet-undiscovered physical laws, the mystery persists. The naturalist paradigm will either have to stretch or give way, but in any case the study of mind reminds us that reality may be more wondrous and complex than any single doctrine. The profound fact that we are conscious invites both scientific scrutiny and metaphysical wonder – a tension that may ultimately enrich both our science and our philosophy.

Sources: Contemporary philosophy of mind and consciousness (Chalmers, Nagel, Searle, Strawson, et al.)consc.netphilosophy.uconn.eduplato.stanford.educonsc.netiep.utm.eduiep.utm.eduplato.stanford.eduweb.mit.eduen.wikipedia.orgen.wikipedia.orgplato.stanford.eduplato.stanford.edu provide primary arguments. Additional discussion is drawn from Stanford/IEP encyclopedias and philosophical literatureiep.utm.eduplato.stanford.edundpr.nd.edu. These sources document both the challenges to naturalism and the positions of its critics.