Explanations of consciousness abound, and the radical diversity of theories is telling. Explanations, or theories, are said to work at astonishingly divergent orders of magnitude and putative realms of reality. My purpose here must be humble: collect and categorize, not assess and adjudicate.^[1] Seek insights, not answers.

Unrealistically, I'd like to get them all, at least all contemporary theories that are sufficiently distinct with explanations that can surmount an arbitrary hurdle of rationality or conceivability.^[2] Falsification or verification is not on the agenda. I'm less concerned about the ontological truth of explanations/theories^[3] than in identifying them and then locating them on a “Landscape”^[4] to enable categorization and assess relationships. Next, I assess implications of categories for “big questions.” Thus, this Landscape is not about how consciousness is measured or evolved or even works, but about what consciousness is and what difference it makes.

It's the classic “mind-body problem:” How do the felt experiences in our minds relate to the neural processes in our brains? How do mental states, whether sensory, cognitive, emotional, or even noumenal (selfless) awareness, correlate with brain states? The Landscape of Consciousness explanations or theories I want to draw are as broad as possible, including those that cannot be subsumed by, and possibly not even accessed by, the scientific method. This freedom from constraint, as it were, is no excuse for woolly thinking. Standards of rationality and clarity of argument must be maintained even more tenaciously, and bases of beliefs must be specified even more clearly.

I have two main aims: (i) gather and describe the various theories and array them in some kind of meaningful structure, or taxonomy, of high-level categories (and under Materialism, subcategories); and (ii) assess their implications, with respect to four big questions: meaning/purpose/value (if any); artificial intelligence (AI) consciousness; virtual immortality; and survival beyond death.

In other words, I seek an organizing framework for diverse theories of consciousness (the taxonomy), and to explore their impact on big questions. My central theses are also twofold: (i) understanding consciousness at this point cannot be limited to selected ways of thinking or knowing, but should seek expansive yet rational diversity, and (ii) issues such as meaning/purpose, value, personal identity, free will, conscious things, AI consciousness, virtual immortality, life after death, etc., cannot be understood except in the light of particular theories of consciousness.

Theories overlap; some work together. Moreover, while a real-world landscape of consciousness, even simplified, would be drawn with three dimensions (at least), with multiple kinds and levels of nestings—a combinatorial explosion (and likely no closer to truth)—I satisfice with a one-dimensional toy model. I array all the theories on a linear spectrum, simplistically and roughly, from the “most physical” on the left (at the beginning) to the “least physical” on the right (near the end).^[5] (I have two final categories after this spectrum.) The physicalism assumed in Materialism Theories of consciousness is characterized by naturalistic, science-based perspectives, while non-materialism theories have various degrees of nonphysicalist perspectives outside the ambit of current science and in some cases not subject to the scientific method of experimentation and replicability.

Please do not ascribe the relative importance of a theory to the relative size of its description. The shortest can be the strongest. It sometimes takes more words to describe lesser-known theories. For each description I feel the tension between conciseness and completeness. Moreover, several are not complete theories in themselves but ways to think about consciousness that strike me as original and perhaps insightful.

I have followed consciousness studies in its various forms for my entire life. My PhD, at UCLA's Brain Research Institute, is in neuroanatomy/neurophysiology (thalamocortical evoked potentials).^[6] I am creator and host of Closer To Truth,^[7] the long-running public television series and web resource on science and philosophy, roughly one-third of which focuses on consciousness and brain/mind topics.^[8] I have discussed consciousness with over 200 scientists and philosophers who work on or think about consciousness and related fields (Closer To Truth YouTube; Closer To Truth website).^[9]

I use these Closer To Truth discussions as resources. I want to give feel and flavor, as well as propositions and arguments, for the astonishingly diverse attitudes and approaches to consciousness coming from radically diverse perspectives and worldviews. That's why I use spontaneous quotes from verbal conversations along with meticulous quotes from academic papers.

In one early Closer To Truth episode, “What are the Big Questions of Science,” philosopher Patricia Churchland gave the bluntest answer: “Out of meat, how do you get thought? That's the grandest question.” She distinguishes two major questions. One is whether psychological states—our mental life of remembering, thinking, creating—are really a subset of brain activity? The other is how do high-level psychological processes come about from basic neurophysiological actions? “How do brain cells, organized in their complex ways, give rise to my watching something move, or seeing color, or smelling a rose” (Churchland, 2000; Kuhn, 2000a, 2000b).

Philosopher David Papineau distinguishes three questions related to consciousness: How?, Where?, and What? “First, how does consciousness relate to other features of reality? Second, where are conscious phenomena located in reality? And, third, what is the nature of consciousness?” (Papineau, 2020a). Because this Landscape is structured by theories of consciousness, not by philosophical questions, each theory sets its own agenda for dealing with the three questions, mostly, of course, focusing on the How?

Philosopher Galen Strawson recounts his sense of the modern history of the mind-body problem in his essay, “A hundred years of consciousness: ‘a long training in absurdity’” (Strawson, 2019). “There occurred in the twentieth century the most remarkable episode in the history of human thought. A number of thinkers denied the existence of something we know with certainty to exist: consciousness, conscious experience.” He labels this way of thinking ‘the Denial,’ and he focuses on two forms of it. ”First, the development of two views which are forms of the Denial —philosophical behaviorism, and functionalism considered as a doctrine in the philosophy of mind… Second, the rise of a way of understanding naturalism—materialist or physicalist naturalism— that wrongly takes naturalism to entail the Denial.”

Philosopher Thomas Nagel sees more a fundamental conundrum and he frames it crisply. “We have at present no conception of how a single event or thing could have both physical or phenomenological aspects, or how if it did they could be related” (Nagel, 1986). In his influential paper, “What Is It Like to Be a Bat?,” Nagel offers, “Without consciousness the mind-body problem would be much less interesting. With consciousness it seems hopeless” (Nagel, 1974).

“Hopeless,” to me, is invigorating; I'm up for the “hopeless challenge.” Take all that follows as my personal journey of consciousness; idiosyncratic, to be sure; not all for everyone, not set in cement.

Chalmers’s “hard problem” of consciousness

Philosopher David Chalmers famously characterized the core conundrum of explaining consciousness—accounting for “qualia,” our qualitatively rendered interior experience of motion-picture-like perception and cognitive awareness—by memorializing the pithy, potent phrase, “the hard problem.” This is where most contemporary theories commence and well they should (Chalmers, 1995b, 1996, 2007; 2014a; 2014b; 2016b).

It is no exaggeration to say that Chalmer's 1995 paper, “Facing up to the problem of consciousness” (Chalmers, 1995b) and his 1996 book, The Conscious Mind: In Search of a Fundamental Theory (Chalmers, 1996), were watershed moments in consciousness studies, challenging the conventional wisdom of the prevailing materialist-reductionist worldview and altering the dynamics of the field. His core argument against materialism, in its original form, is deceptively (and delightfully) simple:

1. In our world, there are conscious experiences.
2. There is a logically possible world physically identical to ours, in which the positive facts about consciousness in our world do not hold.
3. Therefore, facts about consciousness are further facts about our world, over and above the physical facts.
4. So, materialism is false.

This is the famous “(Philosophical) Zombie Argument” (infamous to some): whether creatures absolutely identical to us in every external measure, but with no internal light, no inner subjective experience, are “conceivable”—the argument turning on the meaning and implications of “conceivable” and the difference between conceivable and possible. (It can be argued that the Zombie Argument for consciousness being nonphysical, like the Ontological Argument for God actually existing, sneaks the conclusion into one of the premises.)

Chalmers asks, “Why does it feel like something inside? Why is our brain processing—vast neural circuits and computational mechanisms—accompanied by conscious experience? Why do we have this amazing, entertaining inner movie going on in our minds?” (All quotes not referenced are from Closer To Truth videos on www.closertotruth.com, including 2007, 2014a, 2014b, 2016b.)

Key indeed are qualia, our internal, phenomenological, felt experience—the sight of your newborn daughter, bundled up; the sound of Mahler's Second Symphony, fifth movement, choral finale; the smell of garlic, cooking in olive oil. Qualia—the felt qualities of inner experience—are the crux of the mind-body problem.

Chalmers describes qualia as “the raw sensations of experience.” He says, “I see colors—reds, greens, blues—and they feel a certain way to me. I see a red rose; I hear a clarinet; I smell mothballs. All of these feel a certain way to me. You must experience them to know what they're like. You could provide a perfect, complete map of my brain [down to elementary particles]—what's going on when I see, hear, smell—but if I haven't seen, heard, smelled for myself, that brain map is not going to tell me about the quality of seeing red, hearing a clarinet, smelling mothballs. You must experience it.”

Since qualia constitutes the core of the “hard problem,” and since the hard problem has come to so dominate consciousness studies such that almost every theorist must confront it, seeking either to explain it or refute it—and since the hard problem is a leitmotiv of this Landscape—I asked Dave about its backstory.

“I first remember presenting the hard problem in a talk at the first Tucson ‘Toward a Science of Consciousness’ consciousness in 1994. When did I first use it? Did I use it in writing before then? I’ve looked in my writing and have not found it [i.e., not prior to the 1994 talk]. The hard problem was part of the talk. I remember speaking with some students beforehand, saying I’m going to talk about ‘hard problems, easy problems.’ I had been already talking this way in my seminar the previous year, so maybe it was already becoming part of my thinking. But I didn’t think about it as an ‘insight.’ I just thought it a way of stating the obvious. ‘Yeah, there’s a really hard problem here.’ So, as part of the first couple of minutes of my talk, I said something like ‘everyone knows there is a hard problem’ …. And people took it and said ‘it’s this great insight’ … Well, it did become a catchy meme; it became a way of encapsulating the problem of consciousness in a way that made it difficult to ignore, and I’m grateful for that role. I had no idea at the time that it would catch on, but it’s good because the problem of consciousness is really easy to ignore or to sidestep, and having this phrase, ‘the hard problem,’ has made it difficult to do that. There’s now just a very natural response whenever that happens. You say, ‘Well, that’s addressing the easy problem, but it’s not addressing the hard problem.’ I think this helps in getting both scientists and philosophers to take consciousness seriously. But I can’t take credit for the idea. Everyone knew that consciousness was a hard problem way before me—my colleagues, Tom Nagel and Ned Block; philosophers like C.D. Broad almost 100 years ago; Thomas Huxley back in the 19th century; even Leibniz and Descartes—they all knew that consciousness was a hard problem” (Chalmers, 2016b).

Over the years, while Chalmers has played a leading role in expanding and enriching the field of consciousness studies (Chalmers, 2018), his overarching views have not changed: “I don't think the hard problem of consciousness can be solved purely in terms of neuroscience.” As science journalist George Musser puts it, “By ‘hard,’ Chalmers meant impossible. Science as we now practice it, he argued, ‘is inherently unable to explain consciousness’” (Musser, 2023a, 2023b).

This does not mean, of course, that Chalmers is making a case for “substance dualism,” some nonphysical stuff (like the immortal souls of many religions). Chalmers is postulating a “naturalistic dualism,” where perhaps “information” is the connective, because while information is not material, it is embedded in the physical world. He notes, “We can also find information realized in our phenomenology.” This is a “naturalistic dualism,” a kind of property dualism.

To Chalmers, “It is natural to hope that there will be a materialist solution to the hard problem and a reductive explanation of consciousness, just as there have been reductive explanations of many other phenomena in many other domains. But consciousness seems to resist materialist explanation in a way that other phenomena do not.” He encapsulates this resistance in three related arguments against materialism: (i) The Explanatory Argument (“explaining structure and function does not suffice to explain consciousness”); (ii) The Conceivability Argument (“it is conceivable that there be a system that is physically identical to a conscious being, but that lacks at least some of that being's conscious states”); (iii) The Knowledge Argument (“someone could know all the physical facts … and still be unable to know all the facts about consciousness”) (Chalmers, 2003).

“Physicalists, of course, resist these arguments,” says Philosopher Frank Jackson. “Some deny the modal and epistemic claims the arguments use as premises. They may grant (as they should) the intuitive appeal of the claim that a zombie physical duplicate of me is possible, but insist that, when one looks at the matter more closely, one can see that a zombie physical duplicate of me is not in fact possible. Any physical duplicate of me must feel pain when they stub their toe, have things look green to them on occasion, and so on” (Jackson, 2023).

Philosopher Daniel Stoljar targets the conceivability argument (“CA”). Strictly speaking, he says, “CA is an argument against the truth of physicalism. However, since it presupposes the existence of consciousness, it may be regarded also as an argument for the incompatibility of physicalism and the existence of consciousness.” Stoljar's epistemic view offers a two-part response. “The first part supposes that there is a type of physical fact or property that is relevant to consciousness but of which we are ignorant.” He calls this the ignorance hypothesis. The second part “argues that, if the ignorance hypothesis is true, CA is unpersuasive” for reasons of logic (Kind & Stoljar, 2023, pp. 92, 95).

Philosopher Yujin Nagasawa calls “The Knowledge Argument” (Jackson, 1982, 1986, 1995, 1998) “among the strongest arguments (or possibly the strongest argument) for the claim that there is [in consciousness] something beyond the physical” (Nagasawa, 2012a). Based on a thought experiment by Frank Jackson, it imagines “Mary, a brilliant scientist,” who lives entirely in a black-and-white room, who acquires all physical, scientific knowledge about color—wavelengths of light in all detail—“but it seems obvious that when she comes outside her room, she learns something completely new, namely, what is like to see color.” Prior to seeing the color, “she doesn't have phenomenal knowledge of conscious experience.” While Jackson himself no longer endorses the argument, it is still regarded as one of the most important arguments against physicalism, though of course it has its critics (Garfield, 1996). Nagasawa, who did his PhD under Jackson, responds to critics of the argument (Nagasawa, 2010), but also offers his own objections and novel proposals (Nagasawa, 2008).

Frank Jackson himself has much of the contemporary literature on consciousness revolving around three questions. “Does the nature of conscious experience pose special problems for physicalism? Is the nature of conscious experience exhausted by functional role? Is the nature of conscious experience exhausted by the intentional contents or representational nature of the relevant kinds of mental states?” (Jackson, 1997).

To philosopher Philip Goff, there are two aspects of consciousness that give rise to the hard problem, qualitivity and subjectivity: qualitivity meaning that experiences involve sensory qualities, whether in real-time or via memory recall; subjectivity meaning that there is a subject who has those experiences, that “these experiences are for someone: there is something that it’s like for me to experience that deep red.” Goff argues that these two aspects of consciousness give rise to two “hard problems.” While either problem would be sufficient to refute materialism, he says, the hard problem of qualitivity is more pronounced—or at least easier to argue for—because the vocabulary of the physical sciences, which tell a purely quantitative story of causal structures, cannot articulate the qualities of experience; the language of physics entails an explanatory limitation (Goff, 2021).

Philosopher Colin McGinn provides a culinary perspective: “Matter is just the wrong kind of thing to give birth to consciousness … You might as well assert, without further explanation, that numbers emerge from biscuits, or ethics from rhubarb” (McGinn, 1993).

Philosopher Jerry Fodor put the problem into what he thought would be perpetual perspective. “[We don't know], even to a first glimmer, how a brain (or anything else that is physical) could manage to be a locus of conscious experience. This … is, surely, among the ultimate metaphysical mysteries; don't bet on anybody ever solving it” (Fodor, 1998).

Initial thoughts

Consciousness has been a founding and primary theme of Closer To Truth, broadcast on PBS stations since 2000 and now a global resource on the Closer To Truth website and Closer To Truth YouTube channel. What is consciousness? What is the deep essence of consciousness? What is the deep cause of consciousness? (These are not the same question.) Again, it is the core of the mind-body problem—how thoughts in our minds and sensations of our experiences interrelate with activities in our brains.

What does the word “consciousness” mean? What is its referent? “Consciousness” has multiple definitions, which has been part of the problem in its study. There are clear categories of consciousness, uncontroversially recognized. For example, distinguishing “creature consciousness” (the somatic condition of being awake and responding to stimuli) and “mental state consciousness” (the cognitive condition of experiential engagement with the environment and oneself). More importantly, distinguishing “phenomenal consciousness” (“what it is like”) and “cognitive consciousness” (Humphrey, 2023a, Humphrey, 2023b) or “access consciousness”^[10] (Block, 2023), which are more about function than phenomenology.

Philosopher Ned Block sees “the border between perception and cognition” as a “joint in nature,” primed for exploration. He says he was drawn to this subject because of the realization that the difference between what he calls “access consciousness (cognitive access to phenomenally conscious states)” and what he calls “phenomenal consciousness (what it is like to experience)” was rooted “in a difference between perception—whether conscious or unconscious—and cognitive access to perception” (Block, 2023).

With respect to “information,” it is suggested that “the word ‘consciousness’ conflates two different types of information-processing computations in the brain: the selection of information for global broadcasting, thus making it flexibly available for computation and report,” and “the self-monitoring of those computations, leading to a subjective sense of certainty or error” (Dehaene et al., 2017). But, again, the issue is phenomenal consciousness, and to the extent that each type of consciousness comes with inner experience, the same issues obtain.

Artificial intelligence pioneer Marvin Minsky calls consciousness “a suitcase term,” meaning that all sorts of separate or mildly related concepts can be packed into it. “Consciousness,” he says, “is a clever trick that we use to keep from thinking about how thinking works. And what we do is we take a lot of different phenomena and we give them all the same name, and then you think you've got it.” Minsky enjoys dissecting consciousness: “When people use the word ‘consciousness,’ it's a very strange idea that there's some wonderful property of the brain that can do so many different things—at least four or five major things and dozens of others. For example, if I ask, ‘were you conscious that you touched your ear?’ You might say ‘no, I didn't know I did that.’ You might say, ‘yes.’ If you say yes, it's because some part of your mind, the part that talks, has access to something that remembers what's happened recently with your arm and your ear.” Minsky notes “there are hundreds of kinds of awarenesses. There's remembering something as an image. There's remembering something as a string of words. There's remembering the tactile feeling of something” (Minsky, 2007a).

Minsky says there is no harm in having consciousness as a suitcase term for social purposes. When a word has multiple meanings, that ambiguity is often very valuable, he says. “But if you're trying to understand those processes and you've put them all in one box, then you say, where in the brain is consciousness located? There's a whole community of scientists who are trying to find the place in the brain where consciousness is. But if it's ‘a suitcase’ and it's just a word for many different processes, they're wasting their time. They should try to find out how each of those processes works and how they're related” (Minsky, 2007a).

Philosopher Massimo Pigliucci points out that “you do not need phenomenal consciousness in order to react to the environment. Plants do it, bacteria do it, all sorts of stuff do it.” But when it comes to emotion, he says, “Yes, you do need consciousness – in fact, that is what an emotion is. Emotion implies some level of internal perception of what's going on, some awareness of the phenomenal experience” (Pigliucci, 2023a, 2023b).

Suffice it to say that the hard problem refers to phenomenal consciousness. (This is not to say, of course, that cognitive or access consciousness is an “easy problem.”)

To Àlex Gómez-Marín, a theoretical physicist turned behavioral neurobiologist, “Ask not what neuroscience can do for consciousness but what consciousness can do for neuroscience.” He laments, “When it comes to serious proposals that offer an alternative to materialism, the mainstream has its doors wide shut … I believe the underlying issue of this debate is a tectonic clash about the nature of reality … In other words, the dominant physicalist paradigm can tolerate many things (including its own internal contradictions and empirical anomalies), but not panpsychism, idealism, dual-aspect monism, or any other view … Any nonmaterialist whiff in the consciousness hunger games is punished. Challenge the core foundations, and you shall be stigmatized; propose a cutting-edge new color to the walls of the old building, you will be cheered (Gómez-Marín, 2023).

On the other hand, philosopher Simon Blackburn cautions against overinflating consciousness as a concept. “I wouldn't try to approach it by definition,” he said. “That's going to be just a can of worms. Leibniz said that if we could blow the brain up to the size of a mill and walk around in it, we still wouldn't find consciousness” (Blackburn, 2012).

To Blackburn, the hard problem is not what Chalmers says it is. “I think the really hard problem is trying to convince ourselves that this [consciousness problem] is, as it were, an artifact of a bad way of thinking. The philosopher who did the most to try to persuade us of that was Ludwig Wittgenstein; the central exhibit in his armory was a thing called the private language argument [i.e., a language understandable by only one person is incoherent]. Wittgenstein said if you think in terms of consciousness in that classical way, we meet the problem of other minds. Why should I think that you're conscious? I know that I am, but what about you? And if consciousness in some sense floats free, it might sort of just come and go all over the place. As I say, the hard problem is getting rid of the hard problem” (Blackburn, 2012).

Physicist-visionary Paul Davies disagrees. “Many scientists think that life and consciousness are just irrelevant byproducts in a universe; they're just other sorts of things. I don't like that idea. I think we're deeply significant. I've always been impressed by the fact that human beings are not only able to observe the universe, but they've also come to understand it through science and mathematics. And the fact that we can glimpse the rules on which the universe runs—we can, as it were, decode the cosmic code—seems to me to point to something of extraordinary and fundamental significance” (Davies, 2006a).

To computer scientist-philosopher Jaron Lanier, “Fundamentally, we know very little about consciousness and the process of doing science is best served by humility. So, until we can explain this subjective experience, I think we should accept it as being there” (Lanier, 2007a).

I should note that the mind-body problem is hardly the only problem in consciousness studies: there are myriad mind-related problems. Topping the list of others, perhaps, is the problem of mental causation: How can mental states affect physical states? How can thoughts make actions? Another is what attaches a particular consciousness to a particular person? What makes you, you, and me, me?

Physicist Uzi Awret argues that explaining how consciousness acts on the matter of the brain to “proclaim its existence” is just as hard as explaining how matter can give rise to consciousness. In fact, the two questions constrain each other. (For example, must panpsychists consider phenomenal powers and dualists kinds of interactionism?) Awret makes the insightful point that one reason the two questions should be conjoined is that they can be complementary in the sense that explaining one makes it harder to explain the other (Awret, 2024).

Mental causation is an issue for every theory of consciousness: a serious one for Dualism, less of so for monistic theories—Materialism, Monisms, Idealisms, perhaps Panpsychism-—in that everything would be made of the same stuff. Yet, still, mental causation needs explanation. But that is not my task here.

While precise definitions of consciousness are challenging, almost everyone agrees that the real challenge is phenomenal consciousness. Phenomenal consciousness is the only consciousness in this Landscape.

Neurogeneticist Kevin Mitchell offers fifteen questions that, he says, a theory of consciousness should be able to encompass. Of the fifteen, this Landscape addresses only parts of the first three: What is the basis of subjective experience? What is required for "the lights to be on"? Why do some entities have the capacity for consciousness while other kinds of things do not? (Michell, 2023).

Philosophical tensions

Two types of philosophical tensions pervade all efforts to understand consciousness: (i) epistemological versus ontological perspectives, and (ii) the nexus between correlation and causation. The former distinguishes what we can know from what really exists; they can be the same, of course, but that determination may not be a superficial one and in fact may not be possible, in practice or even in principle. The latter has an asymmetrical relationship in that causation must involve correlation whereas correlation does not necessarily involve causation; the dyadic entities that correlate might each be caused by an unknown hidden factor that just so happens to cause each of them independently.

In addition, there are questions about the phylogenetic evolution of consciousness. Is it a gradual gradient, from simple single-cells seeking homeostasis via stimulus-response to environmental pressures, relatively smoothly up the phylogenetic tree to human-level consciousness (as is conventional wisdom)? Or is consciousness more like a step-function with spurts and stops? Is there a cut-off, as it were? Others, of course, maintain that consciousness is irreducible, even fundamental and primordial.

I give “Philosophical Tensions” its own section, however short, to stress the explanatory burden of which every theory of consciousness must keep cognizant: the epistemology-ontology distinction and the correlation-causation conundrum.

Surveys & typologies

Philosopher Tim Bayne suggests three ways to think about what consciousness is: (i) experience, awareness and their synonyms (Nagel's “what-its-like-to-be”); (ii) paradigms and examples, using specifics to induce the general; and (iii) initial theories to circumscribe the borders of the concept, such that a more complete definition falls out of the theory. Examples of (iii) are conducting surveys and organizing typologies (see below) and constructing taxonomies (which is the intent of this paper) (Bayne, 2007).

To appreciate theories of consciousness, there are superb surveys and typologies, scientific and philosophical, that organize the diverse offerings.

David Chalmers offers that “the most important views on the metaphysics of consciousness can be divided almost exhaustively into six classes,” which he labels “type A” through “type F.” The first three (A through C) involve broadly reductive views, seeing consciousness as a physical process that involves no expansion of a physical ontology [Materialism Theories]. The other three (D through F) involve broadly nonreductive views, on which consciousness involves something irreducible in nature, and requires expansion or reconception of a physical ontology [D = Dualism; E = Epiphenomenalism; F = Monism] (Chalmers, 2003).

PhilPapers (David Bourget and David Chalmers, general editors) feature hundreds of papers on Theories of Consciousness, organized into six categories: Representationalism; Higher-Order Theories of Consciousness; Functionalist Theories of Consciousness; Biological Theories of Consciousness; Panpsychism; Miscellaneous Theories of Consciousness (including Eliminativism, Illusionism, Monisms, Dualism, Idealism) (Bourget and Chalmers, PhilPapers). In presenting a case for panpsychism, Chalmers arrays and assesses materialism, dualism and monism as well as panpsychism (Chalmers, 2016a).

Neuroscientist Anil Seth and Tim Bayne gather and summarize a wide range of candidate theories of consciousness seeking to explain the biological and physical basis of consciousness (22 theories that are essentially neurobiological) (Seth and Bayne, 2022). They review four prominent theories—higher-order theories; global workspace theories; reentry and predictive processing theories; and integrated information theory—and they assert that “the iterative development, testing and comparison of theories of consciousness will lead to a deeper understanding of this most central of mysteries.” However, Seth and Bayne intensify the mystery by observing, “Notably, instead of ToCs [theories of consciousness] progressively being ‘ruled out’ as empirical data accumulates, they seem to be proliferating.” This seems telling.

An engagingly novel kind of survey of the mind-body problem is an insightful (and delightfully idiosyncratic) book by science writer John Horgan (2018). Rejecting “hard-core materialists” who insist “it is a pseudo-problem, which vanishes once you jettison archaic concepts like ‘the self’ and ‘free will’,” Horgan states that “the mind-body problem is quite real, simple and urgent. You face it whenever you wonder who you really are.” Recognizing that we can't escape our subjectivity when we try to solve the riddle of ourselves, he explores his thesis by delving into the professional and personal lives of nine mind-body experts. (He admits it is odd to offer “my subjective takes on my subjects' subjective takes on subjectivity.”) (Horgan, 2019).

While greater understanding of the biological (and material) basis of consciousness will no doubt be achieved, the deeper question is whether such biological understanding will be sufficient to explain, even in principle, the essence of consciousness, ever. While most adherents at both ends of the Landscape of Consciousness—materialists and idealists—are confident of the ultimate vindication of their positions, others, including me, take this deeper question as remaining an open question.

My high-bar attempt here is to generate a landscape that is universally exhaustive, in that whatever the ultimate explanation of consciousness, it is somewhere, somehow, embedded in this Landscape of theories (perhaps in multiple places)—even if we have no way, now or in the foreseeable future, to discern it from its cohort Landscapees.

Opposing worldviews

At the highest level of abstraction, there are two ways to frame competing theories of consciousness. One way pits monism, where only one kind of stuff is fundamental (though manifest in ostensibly different forms), against dualism, where both physical and mental realms are equally fundamental, without either being reducible to the other.^[11]

There are two kinds of monism, each sitting at opposite ends of the Landscape of Consciousness: at one end, materialism or physicalism,^[12] where the only real things are products of, or subject to, the laws of physics, and can be accessed reliably and reproducibly only by the natural sciences; and at the other end, idealism, where only the mental is fundamental, and all else, including all physical existence, is derivative, a manifestation of the mental. (Nondualism, from philosophical and religious traditions originating on the Indian subcontinent, avers that consciousness and only consciousness, which is cosmic, is fundamental and primitive.)

The second way to frame opposing explanations of consciousness is simply the classic physical vs. nonphysical distinction, though certain explanations, such as panpsychism, may blur the boundary.

Is consciousness primitive/fundamental?

A first foundational question is whether consciousness is primitive or fundamental, meaning that it cannot be totally explained by, or “reduced” to, a deeper level of reality. (“Totally” is the operative word, because consciousness can be explained by, or reduced to, neuroscience, biology, chemistry and physics, certainly in large part, at least.)

If consciousness is primitive or fundamental, we can try to explore what this means, what alternative concepts of ultimate reality may follow—though, if this were the case, there is probably not much progress to be made.

On the other hand, if consciousness is not primitive or fundamental, there is much further work to be done and progress to be made. To begin, there are (at least) three next questions:

First, is consciousness “real,” or, on the other hand, is it sufficiently an “illusion,” a brain trick, as it were, which would render consternation over the conundrum moot, if not meaningless?

Second, if consciousness is real (and not primitive), then since in some sense it would be emergent, would this emergence of consciousness be “weak,” meaning that in principle it could be explained by, or reduced to, more fundamental science (even if in practice, it could not be, for a long time, if ever)?

Third, if weak emergence has insufficient resources, would this emergence of consciousness be “strong,” meaning that it would be forever impossible to totally explain consciousness, even in principle, by reducing it to more fundamental levels of scientific explanation.

Finally, is there an intermediate position, where consciousness was not fundamental ab initio, but when it evolved or emerged, consciousness came to become somehow inevitable, more than an accidental byproduct of physical processes? Some see in the grand evolution of the cosmos a process where elements in the cosmos—or more radically, the cosmos itself—work to make the cosmos increasingly self-aware.

Some founders of quantum theory famously held consciousness as fundamental. Max Planck: “I regard consciousness as fundamental. I regard matter as derivative from consciousness. We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulates consciousness” (The Observer, 1931a). Erwin Schrödinger: “Although I think that life may be the result of an accident, I do not think that of consciousness. Consciousness cannot be accounted for in physical terms. For consciousness is absolutely fundamental. It cannot be accounted for in terms of anything else” (The Observer, 1931b). Also, “The total number of minds in the universe is one. In fact, consciousness is a singularity phasing within all beings.” Arthur Eddington: “when we speak of the existence of the material universe we are presupposing consciousness.” (The Observer, 1931c). Louis de Broglie: “I regard consciousness and matter as different aspects of one and the same thing” (The Observer, 1931d). John von Neumann (less explicitly): "Consciousness, whatever it is, appears to be the only thing in physics that can ultimately cause this collapse or observation." John Stewart Bell: “As regards mind, I am fully convinced that it has a central place in the ultimate nature of reality” (Mollan, 2007).

Of course, consciousness as fundamental would eliminate only Materialism Theories. Compatible would be Panpsychisms, Monisms, Dualisms and Idealisms; also, some Quantum Theories and perhaps Integrated Information Theory. (But Materialism has substantial resources.)

Identity theory

I take special interest in identity theory (Smart, 2007), not because I subscribe to the early mind-brain identity theory as originally formulated, but because its way of thinking is far more pervasive and far more elucidating than often realized (though perhaps in a way not as sanguine as some may have hoped).

In PhilPapers’ Theories of Consciousness, Mind-Brain Identity Theory is classified under Biological Theories of Consciousness. Classic mind-brain identity theory is indeed the commitment that mental states/events/processes are identical to brain states/events/processes (Aranyosi, PhilPapers).

I would want to generalize this. I would want to say that any theory of consciousness, to be complete and sufficient, must make an identity claim. Bottom line, every theory of consciousness that offers itself as a total explanation, necessary if not always sufficient—other than those where consciousness is fundamental—must be a kind of identity theory. I mean identity theory in the strong sense, in the same sense that the Morning Star and the Evening Star must both be Venus, such that if you eliminate the Morning Star you cannot have the Evening Star. (David Papineau makes a virtue of this necessity in his mind-brain identity argument for physicalism. It doesn't matter which specific materialist or physicalist theory—all of them, in essence, are mind-brain identity theories [Papineau, 2020b]).

Here's the point. There is some kind of “consciousness identity” actually happening—it is always happening and it never changes. Something happening or existing in every sentient creature just is consciousness.

Haunting thought

If I’d be telling that my lifelong passion to understand consciousness has been motivated entirely by hard-nosed science or cool-coated intellectualism, I’d be telling a fib. A sub rosa motivation has the ever-haunting presence of a teenage thought: “Should a being who can perceive eternity be denied it?”

Robert Lawrence Kuhn

All Landscape Theories. Landscape Categories. Landscape Grid. Landscape Map. Interactive Visualizations.

Landscape Abstract: Diverse theories (explanations) of consciousness are arrayed on a roughly physicalist-to-nonphysicalist landscape of essences and mechanisms. Theory categories: Materialism (subcategories: philosophical, eliminative/illusionism, neurobiological, electromagnetic field, computational & functionalism, homeostatic & affective, embodied & enactive, relational, first-order, higher-order, language, phylogenetic/evolutionary); Non-Reductive Physicalism; Quantum & Dimensional; Information; Panpsychisms; Monisms; Dualisms; Idealisms; Anomalous & Altered States; Challenge. Each theory is self-described by or in the words of its adherents; critique is minimal and only for clarification; and there is no attempt to adjudicate among theories. The implications of consciousness theories (explanations) are assessed with respect to four big questions: meaning/purpose/value (if any); AI consciousness; virtual immortality; and survival beyond death. These questions, I submit, cannot be understood except in the light of particular theories of consciousness. A Landscape of Consciousness, I suggest, offers perspective.

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Footnotes

[1]. Feedback is appreciated, especially explanations or theories of consciousness not included, or not described accurately, or not classified properly; also, modifications of the classification typology. “A Landscape of Consciousness” is a work-in-progress, permanently.

[2]. I make no attempt to be exhaustive historically: while Bohm, Jung, Aquinas, Aurobindo, and Dao De Jing are included; Plato, the Psalmist, Nagarjuna, Confucius, and the Apostle Paul are not.

[3]. I use “explanation” and “theory” interchangeably, though I chose “explanations,” not “theories,” for the subtitle. “Theories” range from the “Theory of Relativity” with high precision, to theories in the life and social sciences with confidence levels that vary wildly, to “I have a theory” (meaning “I have an idea,” about anything, say, why my favorite sports team keeps losing). Other terms are “hypothesis,” an initial idea to guide research, and “model,” a simplification of the real world to isolate and test insights. All these terms have precise definitions in the literature (see Daniel Stoljar, Kind & Stoljar, 2023, pp. 112–113). But on this Landscape everyone picks their own term. Most pick “theory,” in part because they really believe their baby is beautiful. No matter the term, we are all after the same goal: the foundation(s) of consciousness.

[4]. Deliberately, “A Landscape ….” not “The Landscape ….” I acknowledge, with pleasure, precedent to Leonard Susskind's pioneering The Cosmic Landscape (string theory structures and the anthropic principle).

[5]. My typology is arbitrary, and any association with political connotations of “left” and “right” is coincidental and comical.

[6]. UCLA Department of Anatomy and Brain Research Institute, 1964–1968.

[7]. Closer To Truth is co-created, produced and directed by Peter Getzels.

[8]. Closer To Truth features over 100 TV episodes and over 1500 video interviews on consciousness and related topics, issues and questions in brain and mind, such as free will, personal identity, and alien intelligences. Closer To Truth website, www.closertotruth.com and Closer To Truth YouTube channel, www.youtube.com/@CloserToTruthTV.

[9]. In addition, viewers globally send me their theories on consciousness: some are coherent, a few are original, all are passionate. I consider them all—most, admittedly, I skim—and I learn some, enriching the Landscape. There seems a sharp division: those striving to develop purely physicalist explanations (however complex), and those taking consciousness as in some sense fundamental (whether motivated by religion, parapsychology or philosophy).

[10]. The noncognitive nature of perception precludes cognitive theories of consciousness. In particular, Block says there is an argument from one of the cases of nonconceptual perception to the conclusion that there is phenomenal consciousness without access consciousness.

[11]. Logically, there is no necessity for dualism to be the limit; there can be innumerable kinds of irreducible “World-Stuffs”; for this Landscape, monism vs. dualism is sufficiently daunting.

[12]. “Materialism” and “physicalism” are roughly equivalent ontological terms, often used interchangeably, although physicalism can cover wider territory, including properties that the laws of physics describe, e.g., space, time, energy, matter. Moreover, physicalism can connote more epistemological matters, in terms of how we can know things. Materialism can be distinguished as the more restrictive term, meaning all that is real is matter and its equivalents. It connotes more ontological concerns, in terms of what really exists. In this Landscape, we go more with “materialism,” which also maintains historical continuity.