Against the Search for a General Theory of Consciousness

Abstract. Contemporary consciousness research typically assumes that inquiry should progress towards a general theory of the target phenomenon. As a result, prominent accounts like Global Workspace, Higher-Order, and Information Integration theories are being pitted against each other in rigorous adversarial paradigms, presumably in the hope that one general theory will eventually emerge victoriously over all others. On the contrary, I argue that this foundational assumption is mistaken: a general theory of consciousness is unattainable, and therefore should not be a driving goal of consciousness research. Instead, I articulate and defend a staunchly pluralistic “marker” approach that proceeds fruitfully without, and can indeed be hindered by, the search for a general theory. This methodological framework is not only better poised to account for a diverse range of potentially conscious systems (including non-human animals and AI systems), it justifies the proliferation of different theoretical camps in the field of consciousness research.

1. Introduction

The empirical study of consciousness has seen a rapid upsurge of academic interest in the past few decades, and important progress has been made on both experimental (Boly et al. 2017, Malach 2021) and theoretical (Dehaene et al. 2021, Birch 2022) fronts. Among the philosophers and scientists that work on consciousness, most operate on the assumption that our inquiry should eventually culminate in a single “general”, “secure”, “unified”, or “comprehensive” theory of the target phenomenon (Block 2009, Koch 2019, Doerig et al. 2020, Melloni et al. 2021, Mudrik et al. 2023, Andrews 2024). In what follows, I reject this foundational assumption: a general theory of consciousness is unattainable, and therefore should not represent the field’s driving goal.

Several well-known conceptual frameworks have emerged that purport to offer general accounts of consciousness, including Global Workspace (Dehaene 2014), Higher-Order (Brown et al. 2019), and Information Integration (Tononi et al. 2016) theories. It is widely assumed that a theory of this sort not only helps to structure and guide ongoing research, but that successfully establishing a general theory is necessary if we want to confidently ascribe and study consciousness in a range of different systems. The idea is that without a widely accepted, comprehensive theory of the target construct, we ultimately lack the appropriate conceptual foundations for making accurate and reliable ascriptions of particular instances of consciousness across different contexts. This, in turn, has pressing social, political, and moral implications (Dehaene et al. 2021, Mudrik et al. 2023, Andrews 2024). Melloni et al. (2021) write:

“A comprehensive and agreed-upon theory of consciousness is necessary to answer the question of which systems—biologically evolved or artificially designed—experience anything and to define the ethical boundaries of our actions toward them.”

That we should collectively aim to establish a single, comprehensive, shared, “stable” theory of consciousness seems to have become the primary goal of most research programs in the area (Seth & Bayne 2022, Andrews 2024). This is certainly reflected in the current state of affairs, where, for instance, much effort is being directed towards adversarial paradigms that pit the most prominent general theories against one another, presumably in the hope that one will eventually emerge victoriously over all others (Melloni et al. 2021, 2023, Chis-Ciure et al. 2024). However, we are far from reaching consensus in terms of which theoretical framework might be “correct”, such that it ought to be adopted by the field at large.

In Section 2, I explore the logic underlying the notion of a general theory of consciousness, and consider some of the different possible paths that one might take to attempt to get there. This analysis aims to expose insurmountable conceptual obstacles inherent in the primary routes to a general theory of consciousness. In Section 3, I’ll systematically articulate and defend an alternative approach to interdisciplinary consciousness research; namely, a staunchly pluralist version of the so-called “marker methodology”. I’ll argue that this framework represents an indispensable and fundamental form of naturalistic inquiry that proceeds fruitfully in the absence of a general theory. In the final Section 4, I’ll draw out three different kinds of conclusions (of increasing boldness) concerning the possibility of establishing a general theory of consciousness.

2. What Are We Looking for in a Theory of Consciousness?

Despite the appearance of controversy, the target of inquiry in contemporary consciousness research seems undisputed. The goal is to understand that feature of the world that related terms like “experience” or “awareness” or “sentience” have helped us triangulate (Koch et al. 2016, Bayne et al. 2024, Birch 2024); that central fact of our own existence as (human) biological organisms that there is often “something it is like for us” (Nagel 1974, Melloni et al. 2023). It is a foundational scientific assumption that some processes carried out by some complex systems have a distinctly “subjective” or “intrinsic” quality for the system itself (Koch 2019), and some do not. The concept CONSCIOUSNESS has clear explanatory power in both folk and formal ontologies, such that despite its (perhaps unavoidably) egocentric and anthropocentric origins, it is widely invoked to explain the behaviour of a range of biological, and perhaps eventually artificial, systems (Godfrey-Smith 2024, Birch 2024). Theoretical and empirical programs alike certainly can and do proceed fruitfully with this sort of abstracted description that serves to pick out the target of inquiry.

In contrast, it remains unclear what a comprehensive general theory of consciousness is supposed to look like, beyond some foundational and uncontroversial epistemic criteria. On all accounts, for instance, a “general” theory obviously ought to be broadly generalizable (Doerig et al. 2020, Mudrik et al. 2023); in the sense that it should be applicable to the widest possible range of potentially conscious systems. A general theory should also isolate what is distinctive or unique about the target of inquiry (Ludwig 2022); that is, it should aim to pick out features or properties, like specific neurobiological mechanisms or psychological functions, that are only present when consciousness is present. The latter criterion is particularly important; indeed, unique properties provide the materials for effective generalization in the first place. Unique, not shared, features are what allow us to reliably distinguish concrete cases of conscious and unconscious processing. The unique features of the Dwarf Carnation, by analogy, like its particular arrangement of densely packed petal blooms, are what allow us to distinguish it from the other flowers in the garden, and in principle, any garden in the universe. Simply knowing that all Dwarf Carnations use photosynthesis—while being highly generalizable and informative about the broader classes of phenomena that share this feature, like “flowers” or “plants”—is fairly uninformative about one specific flower we are interested in distinguishing from the others. The same is true about consciousness: unique features allow us to distinguish it from other psychological phenomena, specifically unconscious psychological phenomena, and hence to reliably ascribe it in a range of different contexts. Taken together then, this sort of generalizability by way of uniqueness represents the epistemic core of any plausible candidate theory of consciousness.

The logic of necessity and sufficiency can also help to further illuminate the formal structure behind claims about the structural or functional features of consciousness processing (Chalmers 2000, Ludwig 2022). A structural or functional feature can be said to be necessary for consciousness if it is present in every case of conscious experience; that is, if it is maximally generalizable. In contrast, a marker can be said to be sufficient for consciousness if no unconscious processes are marked by this feature; that is, it is a unique feature, and so its presence is enough to assume the presence of conscious experience. This logical framework can indeed help render claims about candidate markers of consciousness more precise, and further illustrate what a general theory of consciousness must amount to (Michel & Lau 2020). Crucially, general theories of consciousness like GWTs, HOTs, and IITs can be naturally interpreted as making necessity claims: claims that the purportedly unique features that these theories have identified in their comparisons with unconscious processing (i.e., the global workspace, metarepresentation, integration) are maximally generalizable to all conscious experiences (Lau 2022, Birch 2024).

Such foundational epistemic assumptions seem to be shared by consciousness researchers (and at least botanists too), and yet the explanatory commitments of a general theory still often fail to be made explicit. But here's the crux of this issue: establishing a single, comprehensivetheory of consciousness seems to entail successfully achieving maximal generalizability by way of uniqueness—once and for all. That is, for a comprehensive general theory to be successful, it must pick out the full set of unique (i.e., sufficient) features of the target of inquiry, such that it can ground a “complete” set of generalizations about the presence of that target in different candidate systems. Holding out hope that the field will eventually settle on the general theory of consciousness, then, entails expecting a theory that will be applicable to every possible instance of consciousness across space and time, precisely because it will pick out the full set of (e.g., neurobiological, psychological) properties that are unique to all the different manifestations of consciousness.

Some research programs are more explicit about these underlying explanatory commitments than others (Michel & Lau 2020). In a recent paper, Kanai and Fujisawa (2024) argue that in order to “cope” with the multiple realizability of consciousness across different systems, our theories ought to strive for universality. They recognize that a successful theory of consciousness would have to be “consistent and apply equally everywhere in the universe, and remain the same over time” (Kanai and Fujisawa 2024, p. 2). IIT’s advocates also tend to be fairly explicit about the fact that their theory purports to pick out the set of systemic properties that are uniquely associated with consciousness, which must be present in, or are “required by” (Tononi et al. 2016 p. 450) any system that can be said to be conscious. Similarly, whether explicitly stated or not, both GWT and HOT advocates must assume that if they turn out to be “correct” and are to be adopted as the general theory of consciousness, it’s because they pick out the full set of (e.g., neurobiological, psychological) features that are unique to consciousness (Dehaene et al. 2021). Given this formal illustration of what seems to constitute a general theory of consciousness, there are a few salient paths that one might try to take to get there.

2.1 A Reigning Champ

The accounts that have risen to prominence in the field, like GWTs, HOTs, and IITs all propose general theories of consciousness in terms of its mechanistic implementations and/or psychological functions. Might one of them ultimately turn out to be “correct”? There are strong reasons for assuming that no single theory is in a position win out over all others. Rather, each theory likely picks out a set of features that, while perhaps highly or even uniquely associated with the presence of consciousness, are not present in every single instance of conscious experience across all of time and space. Counterexamples entail that any one of these theories needs to be supplemented—perhaps indefinitely—if it is to have a hope of achieving maximal generalizability. The idea is that none of these theories have given us the full set of (e.g., neurobiological, psychological) features that are unique to consciousness such that we can reliably ascribe it in any possible candidate system. Specific counterexamples to these theories’ claims to maximal generalizability (i.e., necessity) have been discussed in detail elsewhere (e.g., Boly et al. 2017, Paul et al. 2020, Birch et al. 2020, Ludwig 2022).

However, note a few well-established counterexamples that challenge the explanatory scope of general theories. Contrary to GWTs and HOTs in particular, Block (2023) has recently made the case that while infant color perception exhibits other plausible markers of experience—namely, habituation (discussed below)—it is neither accessed for global broadcasting nor the subject of higher-order processes like metarepresentation or reality monitoring. Arguments for conscious “overflow” similarly provide compelling examples of visual (Usher et al. 2018) and emotional (Smith 2019) experiences that occur in the absence of focal attention, which is widely assumed to be an essential “prerequisite” for executive functions like global broadcasting and higher-order representation (Dehaene & Changeux 2011, Lau 2022). Recent work on the phenomenon of ASMR also suggests that vivid sensory-emotional experiences (i.e., pleasant tingles) unfold precisely when focal attention is otherwise occupied, or “suspended”, by a trigger stimulus (e.g., soft speech sounds, see Ludwig & Khalidi 2024). On the contrary, denying experience to systems that lack the neurofunctional features characteristic of the adult human prefrontal cortex forces counterintuitive, neo-Cartesian explanations of behaviour; for example, denying that an infant experiences pain when they wail after getting seriously hurt, or that a dog experiences something akin to joy when they run frantically in circles upon their caregivers return.

Similarly, it is likely that some conscious experiences lack the structural-functional features that IITs assume to be maximally generalizable to any conscious system: a “central complex” of irreducibly integrated information (Koch 2019). First, there are reasons to doubt IITs’ motivating intuition in the first place: the deeply rooted philosophical doctrine (Descartes 1649, Husserl 1960), that experience necessarily exists as a unified “whole”. In other words, it is important that we evaluate the dogmatic assumption that the unity of consciousness is an indisputable axiom that is to be easily derived from introspection (Albantakis et al. 2023, Bayne 2012, Koch 2019, Masrour 2020). Instead, the totality of my own conscious experiences at any one time seems more like a constantly shifting galaxy of intricate, but quite disconnected, constellations of perceptual, emotional, and motor information, with a nebulous stream of inner speech meandering throughout. Meanwhile, my (overly active) attention flits across this vast landscape in a seemingly chaotic manner, as I navigate even simple sensory-motor tasks like crossing the street.

On theoretical grounds, sustaining maximal integration of all conscious information seems far too demanding for psychological systems that seem to value efficiency and avoid redundancy when possible. We might, for example, need to integrate visual and emotional information when deciding which painting to buy for our home, but we need not if we are simply deciding which painting to move out of the way while simultaneously “feeling” cranky. Note too that while integration is certainly one processing strategy employed by highly complex systems like the human cerebral cortex, (characterized, for instance, by dense recurrent and lateral connectivity), such structures also enable impressive feats of parallel processing. At the very least then, it is a genuine conceptual possibility that maximal information integration is not always a feature of the totality of a system’s experiences at any one time, and thus that some psychological and behavioural capacities are supported by unintegrated experiences (de Haan et al. 2021).

There are empirical programs that lend support here as well. The rich literature on interference effects in dual-task paradigms, for example (Fernandes & Moscovitch 2000, Bayot et al. 2018, Nedergaard et al. 2023), seems to reliably demonstrate simultaneous conscious processes that remain unintegrated. One paradigm—the articulatory suppression paradigm (Richardson & Baddeley 1975)—demonstrates that verbally producing a string of random phonemes interferes with a subject’s ability to simultaneously perform everything from visual search to executive task switching (Fatzer & Roebers 2012, Camos et al. 2013, Cronin et al. 2020). On at least some versions of these experiments, both the “supressing” voluntary verbal behaviour and the concurrent task demand (e.g., visual search) are carried out consciously by subjects during dual-task performance. But these processes plausibly remain unintegrated in the sense stipulated by IITs. On the contrary, the contents of these conscious processes work against each other in producing an intended behaviour. It is hard to make sense of this sort of conscious “interference” or “conflict” in dual-task performance on the IIT model.

Other experimental paradigms aim to directly manufacture failures of conscious integration in laboratory settings. Psychophysicists exploit certain stimulus contexts, such as when objects are moving at high speeds across the visual field, in order to manipulate and ultimately model the temporal structure of visual object perception. Some experimental designs have produced stark dissociations in the temporal structure of visual object perception; for instance, between the processing of properties like direction of motion and colour (e.g., Clifford et al. 2004, Holcombe 2009, Brogaard et al. 2021). In other words, when target stimuli are moving at high speeds, subjects reliably report experiences in which colours are “disembodied” from their objects. This is because colour is processed further downstream, and hence happens later and is slower, than visually indexing an object and determining its direction of motion. I have similarly unintegrated experiences of properties (especially of the colour of objects) every time the subway speeds past and I try to fixate on the individual passengers. Note that in these cases, even with the temporal lag these are simultaneous experiences of an object in motion and a disembodied colour that are unintegrated in the technical sense stipulated by IITs.

The point of identifying these counterexamples, however, is not to then reject these theoretical frameworks wholesale, as if they have nothing to contribute to the ongoing empirical study of consciousness. On the contrary, if their theoretical posits—e.g., the global workspace, higher-order representation, information integration—can be appropriately qualified and articulated in such a way that they turn out to involve structures and functions that are unique to consciousness, then each theory might pick out a reliable feature or marker that supports a limited range of generalizations. It is certainly possible that new theories and their associated markers could emerge that afford increasingly broad generalizations across increasingly divergent kinds of systems. But these counterexamples strongly suggest that no one theory alone, including the existing (extensively researched and developed) theoretical frameworks that have risen to prominence, seems capable of winning out over the others as the sole correct account of the structural-functional properties that are unique to consciousness, such that the theory is generalizable to every instance of conscious experience across space and time. Given this state of affairs, there seem to be a few other possible paths to a general theory of consciousness.

2.2 Convergence

Another potential path to a general account involves the eventual convergence of different theories of consciousness. In practice, distinct research programs are largely developed independently of, in contrast to, and even in conflict with one another (Melloni et al. 2023). Perhaps a more collaborative effort could lead to theoretical convergence among consciousness researchers (Del Pin et al. 2021, Evers et al. 2024).

To illustrate, Dehaene et al. (2021) recognize that GW and HO theories emphasize two different psychological functions that are both highly associated with (and perhaps unique to, or sufficient for) conscious experience in humans: the global broadcasting of select information (which facilitates behavioural flexibility) and the self-monitoring of that broadcasted information (which facilitates a “subjective sense of certainty or error”, p. 44). They conclude by endorsing a sort of hybrid general account, such that both of these distinct functions are hypothesized to covary with the presence of conscious experience (Dehaene et al. 2021). In addition, IIT emphasizes a different aspect of consciousness that is at least conceptually compatible with GWT and HOT, namely the long-standing idea that experiences are the result of causally complex processes that integrate disparate information into unified “wholes” (Koch 2019). We might therefore hold out hope that there is a general, overarching theoretical framework that can consolidate the insights of some or all of the most promising theories of conscious experience.

Others have argued that a more temporally extended perspective on conscious psychological processes could help us achieve theoretical convergence (Kent & Wittman 2021). For instance, Northoff and Lamme (2020) argue that “different theories concern distinct aspects of both neural activity and consciousness which may be integrated and nested within the brain’s overall temporo-spatial dynamics.” Indeed, many researchers adopt a narrower, more temporally “static” understanding of the target of inquiry than is available to us, such that it is common to speak of discrete, stable conscious states rather than complex, dynamic conscious processes. The hope here is that such a shift in ontological perspective might reveal the full profile of component structural-functional elements involved in conscious experience. Ideally, “correct” theories will then map on to a different aspect of this spatiotemporally dynamic phenomenon, and we will ultimately be able to draw from all of this a stable overarching theory of consciousness that in some way conceptually unifies all of the contributing research programs.

There are, however, obstacles to theoretical convergence among consciousness researchers. One conceptual obstacle is that the logic of convergence suggests that an indefinite number of theories might make the case that they have something to add to the overarching explanatory framework, rather than just the prominent theories on offer. To illustrate, some research has uncovered a strong associative relationship between certain emotional regulatory processes and conscious experience (e.g., Szczygieł et al. 2012, Ginot 2015). In isolation from other theoretical frameworks and their constructs, one could (and should!) eventually develop an “Emotional Regulation” (ER) theory of consciousness: consciousness is characterized by a distinct subset of capacities for emotional regulation. A corresponding empirical program could emerge as well, ideally using facts about consciousness’ role in emotional regulation to derive reliable markers of experience. There is no reason why this perspective on the phenomenon should be excluded from the roundtable that makes up a unified theory of consciousness. As long as it picks out a unique feature of conscious processing and hence can reliably support a significant enough range of generalization and prediction, the distinct framework—as formulated—should be thought to partially contribute to our overall theoretical and empirical grasp on the target of inquiry.

An important point that keeps emerging here is that conscious experience is radically multiply realized, and thus theoretical convergence can easily become unwieldy. ‘Consciousness’ is a high-level psychological construct that seems to be realized by an indefinite and incalculable range of different structural mechanisms, supporting an indefinite and incalculable range of different functional capacities. In humans alone, the range of different types of experience we might enjoy, and their structural and functional properties, has not been appreciated in mainstream consciousness research. Consider how structurally-functionally different consciously smelling gasoline is from consciously planning a vacation or from consciously feeling severely depressed. Nor have we appreciated the extent to which fundamental differences in the structure of experience across individuals might explain some discrepancies between competing empirical research programs (Lupyan et al. 2023). Remember too that consciousness is thought to be present first and foremost in biological systems that are continuously evolving, suggesting that new selection pressures could ultimately favour new kinds of experience that are currently unfamiliar to us. Research on the presence of consciousness in different sorts of biological and even artificial systems is now flourishing (Birch 2024), exhibiting the ongoing application of the construct to new kinds of experiences in different kinds of systems.

A general theory therefore needs to take this radical multiple realizability of consciousness into account if it is going to successfully achieve maximal generalizability. However, a single comprehensive account would need to be stretched pretty thin, and would seem to ultimately require indefinite ongoing amendment, in order to achieve this. Any similar suggestion of this kind of “reconciliation” among theories (e.g., Seth & Bayne 2022) or broadening the inclusive scope of our working general theories (Andrews 2024) will immediately confront the fact that consciousness is characterized by a “wildly disjunctive” class of lower-level structural-functional properties (Fodor 1980).

But even in the absence of widespread theoretical proliferation due to radical multiple realization, it is not obvious what a “converged” theory would look like, nor how it would support ongoing generalization and prediction in consciousness research. Even if, for the sake of argument, only GW and HO turn out to be accurate theories, the resulting picture is that our explanation of the distinct structural and functional features of consciousness form a sort of “disjunctive” kind (ala Fodor, 1980). At the very minimum then, consciousness would be explained by two distinct underlying structural-functional markers, and we would have a “GW and/or HO” theory of consciousness.

Part of Fodor’s lesson about multiple realization, however, is that taken together, the disjunction of “lower level” explanation does not have the right formal structure to enter into scientific laws and to support ongoing generalization and prediction. Instead, each lower-level explanation (e.g., explanations of consciousness in terms of some set of its unique neurobiological and psychological properties) represents a distinct claim about a particular relation between the higher-level construct and one of its multiple possible realizations or manifestations. Different lower-level explanans—like the global workspace, intrinsic causal power, or emotional regulation—can be mutually informative and may even collapse into unified hypotheses. But lower-level explanations can also represent utterly distinct claims about structural and functional properties that indicate the presence of consciousness, especially relevant to radically different systems. In other words, distinct theories can (and do) pick out different unique features of consciousness that ultimately dissociate from one another. Conscious system A can have a structural/functional feature (e.g., the capacity for higher-order reality monitoring in humans) that conscious systems B doesn’t, and vice versa (consider the capacity for fine grained olfactory representation in dogs). The role that higher-level constructs like “consciousness” play is precisely to capture some property of the world that is shared among its different manifestations, even those with utterly distinct underlying structural-functional properties.

As such, an approach that remains open to a diversity (or plurality) of lower-level explanations, where each tracks different manifestations of the target higher-level property, will give us a more accurate, nuanced, and complete picture of that target property than one that tries to emphasize and restrict inquiry to only one or a few of these lower-level explanations. Such an approach leaves the door open for an ever-expanding scope of novel lower level “theories”, each of which aims to pick out structural and functional features of different realizations of experience. In sum, arriving at a theory of consciousness in the form of a hybrid model born from the convergence of different lower-level explanations cannot be appropriately characterized as constituting a single, unified, coherent, general theory. This is true even if only a small number of theories turn out to be successful, and thus the hybrid theory avoids being an unwieldy disjunction of views (e.g., GW and/or HO). In formal terms, theoretical convergence via (perhaps indefinitely) iterative disjunction is different in logical structure than formulating a comprehensive, general theory that unifies explanation into a single theoretical framework.

2.3 Answering the Hard Problem

For some philosophers, a successful general theory of consciousness will involve not only giving an account of its mechanistic implementations and/or psychological functions, but also saying something about why or how consciousness is associated with the structures and functions that it happens to be associated with. Dubbed the “hard problem” by Chalmers (1995), the challenge is that any theory that seeks to explain consciousness in terms of its structural or functional features must also have a satisfying account of the nature of the metaphysical relationship between the explanandum and explanans. The conceptual possibility that consciousness could be carved out of the “’physical” or “natural” world with no change to the behaviour of the systems therein is taken to support the deeply rooted belief (or desire) that consciousness is radically distinct from its underlying structural and functional features. This metaphysical assumption, in turn, ultimately grounds the bold epistemological charge that the natural sciences are ill-equipped to explain experience, construed in these discussions as an ontologically sui generis (e.g., “first-person”) phenomenon (Chalmers 2017).

One primary underlying motivation for this kind of challenge to the viability of a science of consciousness is the assumption that consciousness is a distinctly “special” or unique property in the universe, and thus poses unique challenges to scientific inquiry (Lee 2019, Del Pin et al. 2021). As such, it is often assumed that without an account of why or how this special property is related to regular old natural (e.g., structural and functional) phenomena, science fails to say anything substantial about the very thing we are trying to understand. Indeed, to this day many philosophers (Andrews 2023, Heylighen & Beigi 2024) and now scientists (Melloni et al. 2021, Cleermans & Tallon-Baudry 2022) proceed on the assumption that answering the hard problem would be the pinnacle of success in the empirical study of consciousness. Such an answer would precisely explain the relation between experience and all of its structural and functional manifestations, and a successful, stablegeneral theory of consciousness would follow directly.

However, this path to a general theory of consciousness is also fraught with conceptual obstacles. First, it is important to note that this challenge is not unique to the empirical study of consciousness. Similar questions can be asked about all kinds of higher-level properties that have metaphysical relations to lower-level properties (Churchland 1985). It remains mysterious, for example, why and how “wetness” bears a metaphysical relation to the activity of certain lower-level molecular structures, or why and how social institutions like “governments” or “music scenes” bear a metaphysical relation to the activity of individual psychological systems, even when we have a fairly good account of what those lower-level properties are. So, while consciousness does seem to be a “special” property in the natural world, it should not be construed as especially special, or “peculiarly difficult to understand” (Lee 2019). In other words, the natural sciences consistently confront these sorts of wacky metaphysical relations—biologists study “digestion” by looking at the activity of enzymes, climatologists study “climates” by looking at localized weather patterns—and yet proceed with robust research programs that track explanatorily significant relations between levels of explanation, despite failing to answer their own “hard problems” (Miracchi 2019). This all casts doubt on the idea that the hard problem of consciousness has to be answered.

Second, it is unclear that this question can be answered, as it is unclear what form an answer to the hard problem is expected to take. Take the analogy of “wetness”: it is not clear how one might even go about explaining the metaphysical relation between this property and the activity of certain molecular structures, despite the undeniable fact that such a relation exists. One interested in explaining or understanding “wetness” as a construct can pose a similar challenge: “You’ve only told me about the activity of H2O, but where does the ‘wetness’ enter the picture? Precisely why or how is‘wetness’associated with these molecular structures and not others?”. It seems equally possible to conceptually isolate wetness from the molecular composition that realizes it; imagine “zombie water”, some stuff with the same molecular structure as liquid H20, but that is not accompanied by wetness. Ultimately, one might pose a similar skeptical challenge to the science of fluid dynamics that we see aimed at the science of consciousness.

But the progression of the natural sciences has instead involved embracing and exploring these sorts of relations between different “universes of scientific discourse”, without well-defined or articulated metaphysical theories of the nature of these relations in place. In the end, these relations might just be brute facts about properties in complex systems that admit of different “levels” of explanation (Wimsatt 1994). Insisting that we must answer these metaphysical questions if we want to proceed with confidence in the empirical study of consciousness places much higher explanatory standards on consciousness as a target of inquiry than we see with research on other higher-level (e.g., psychological) properties of complex systems. Within the domain of cognitive science, we don’t know, for instance, why or how attention bears a metaphysical relation to certain underlying neural and psychological features and not others, but a robust interdisciplinary research program on attention proceeds nonetheless (Carrasco 2011).

To summarize, it is not clear a) why such deep metaphysical questions must be answered about consciousness in order to proceed with a robust empirical research program, but not other objects of (e.g., psychological) scientific inquiry, and b) whether these questions can even be answered in principle. The problems dubbed “easy” by Chalmers (2017) provide the resources for robust empirical research programs that can help us understand consciousness and its various manifestations in the natural world (Miracchi 2019). I conjecture that it is the false conceptualization of consciousness as something that is in some way utterly anomalous or “especially special” in the natural world, and therefore radically distinct from its structural-functional properties, that helps sustain the illusion that there is a problem here in the first place. For these reasons, it seems unlikely that an answer to the hard problem will provide the materials for a successful general theory of consciousness.

2.3 Definition

Another potential path to a general theory of consciousness involves trying to formulate a definition of the target of inquiry that in some way successfully captures the referential scope of the corresponding scientific construct. Philosophers have long toiled over various definitions and applications of the term ‘consciousness’, with many assuming that an accurate, formalized account of this kind will fix the relevant empirical construct, and facilitate its systematic use among disparate consciousness researchers (Searle 2017). A rigorous definition, if achievable, could provide indisputable grounds for evaluating claims about the presence of consciousness in any possible candidate system (Gennaro 2018). A successful definition should therefore directly yield a successful general theory of consciousness. A precise definition would represent a conceptual point of reference that is maximally generalizable, because it in some way provides a comprehensive account of the features that are unique to consciousness. However, many definitional projects simply pick out an abstracted, working characterization of the construct that serves as a target of further inquiry. It is crucial to realize that while intimately linked, this project is importantly different from the project of tracking features that characterize the diverse manifestations of those constructs in the world.

Accounts that do purport to say something about the defining features of consciousness, in contrast, typically follow from the sorts of theories already on offer. GW theories, for example, purport to offer “a precisely defined empirical construct” (Baars 2017, p. 231), while HO theories have been explicit in claiming that “what defines a conscious system is the ability to have higher-order thoughts” (Gennaro 2018, p. 150). Similarly, recent attempts to reconcile GW and HO theories (Dehaene et al. 2021) unsurprisingly culminate in a “functional definition” of the target phenomenon; a hybrid theory that defines consciousness in terms of the computations underlying both access-for-broadcasting and metacognitive monitoring. Finally, IIT claims to provide a definition of consciousness in terms of the maximally irreducible, intrinsic causal power in a system (Tononi et al. 2016).

There are reasons, however, for assuming that these sorts of theories do not provide the materials for a successful definition of consciousness. For example, again, there is sufficient theoretical and empirical support to suggest that experience occurs in the absence of Prefrontal Cortex (PFC)-driven computations (Usher et al. 2018, Schlossmacher et al. 2020), and that humans and non-humans that lack prefrontal structures show other markers of conscious experience (Boly et al. 2017, Pennartz et al. 2019). These points seem to warrant the conclusion that a definition based on the kinds of computations described by GW and HO theories, one that excludes any kind of experience not related to PFC-driven executive psychological functions, will be too narrow in its explanatory scope.

But this specific criticism reflects a deeper problem inherent in the attempt to offer a definition of a notion like ‘consciousness’ in terms of the features of its structural and functional manifestations. The recurring obstacle is that even if a theory can support a significant enough range of generalizations and predictions to become a viable research program, there is no reason, no way—and no need!—to claim that the theory will be applicable to every instance of conscious experience to ever exist in the universe (i.e., will achieve necessity or maximal generalizability). Defining ‘consciousness’ in a way that is relevant to the natural sciences again reduces to the impossible task of providing a concise, complete, unchanging account of the mechanistic and/or functional features underlying its varied manifestations.

This is just the nature of definition: if it is “correct” or “accurate”, then the definition must in some way precisely outline the scope of the term’s possible applications. But precise and stable definitions are difficult to articulate even for simple terms like ‘chair’ that are also manifested in a variety of ways in the natural world (Wittgenstein 1953). The trajectory of consciousness research has been a continued revelation that experiences manifest in a multitude of ways, in a multitude of different systems. Thus, expecting a definition that once and for all captures the correct scope of the application of the term ‘consciousness’, especially as conscious biological systems continue to evolve and we face the possibility of conscious artificial systems, seems to be a misguided approach. Once again, while it’s not clear that we can provide a definition of consciousness that will ground a general theory, a comprehensive definition of consciousness doesn’t seem to be needed in order to focus disparate research programs on a common target of inquiry.

2.4 Interim Summary

The most obvious paths to a general theory of consciousness seem fraught with significant, perhaps insurmountable, conceptual obstacles. Fortunately, the empirical study of consciousness need not achieve a general theory in order to make significant progress on the shared goal of understanding conscious experience and its place in the natural world. On the contrary, I’ll argue that the quest for a general theory can actually be detrimental to progress in contemporary consciousness research, when it restricts inquiry to a (e.g., anthropocentric, visuocentric) subset of lower-level explanations of the target higher-level property. In the next section, I articulate and defend an alternative approach.

3. Markers of Consciousness

3.1 Neural Correlates and Functional Contributions

The attempt to identify reliable structural and functional “indicators” or “markers” has become one of the dominant methodological approaches to the empirical study of consciousness. The search for structural markers in particular, or neural correlates of consciousness (NCCs), has long taken centre stage in both philosophical (e.g. Metzinger 2000) and scientific (e.g. Crick & Koch 1994) discussions. Statistical analyses of neuroimaging data could potentially be used to isolate neural activity that is (minimally) sufficient for consciousness (Chalmers 2000). The goal here is to try to “subtract” out the neural activity that is truly responsible for consciousness and its specific contents, again by comparing patterns of neural activity during conscious versus unconscious performance on the same task, such as word recognition (Dembski et al. 2021, Malach 2021). The more evidence we can marshal for the uniqueness or sufficiency of a candidate neurobiological marker of consciousness, the more that marker ought to be able to support stable generalization and prediction, and ultimately act as a reliable operationalizable proxy for conscious experience in ongoing research.

Using the same comparative methodology, we can also try to isolate functional (i.e., psychological, behavioural) phenomena that are only present when conscious experience is also present (e.g., Szczygieł et al. 2012, Koivisto & Rietamo 2016, Lamme 2020, Ludwig 2022). However, beyond mere claims of correlation, strong positive covariance here suggests that there are functional or causal capacities that exist as a result of conscious experience. Despite lingering doubts about the causal efficacy of conscious experiences (Chalmers 2017, Kozuch 2021), the inferences involved here are familiar across the sciences. On a broadly causal interventionist approach to scientific explanation, intervening on or manipulating a target variable while holding all else equal [1] reveals the causal role(s) that variable plays in the system that it is a part of (Woodward 2017). Experimental manipulations and clinical pathologies form the evidential core of contemporary consciousness research, and these causal interventions tell us about psychological functions that are facilitated by consciousness; that is, they are functional contributions that consciousness makes to the system (FCCs, Ludwig 2022). Once again, with enough support in favour of the uniqueness of a candidate FCC, this functional marker can be used as an operationalizable proxy for consciousness in future research. It should also be noted that while we can think of investigations into structure and function as representing two distinct strands of research for distinct scientific disciplines, they are intricately interwoven projects. In other words, searching for structural (NCCs) and functional (FCCs) markers of consciousness is typically mutually informative (e.g. Lamme 2020).

Note that this general methodological approach, dubbed the “marker method”, characterizes most, if not all, serious research programs dedicated to the empirical study of consciousness. This is true even when the method is only implicit in empirical paradigms and theoretical discussions. For instance, major theories like GWTs, HOTs, and IITs have ultimately been offering candidate markers of consciousness, in that they claim to be identifying neural and/or psychological phenomena that reliably signify the presence of conscious experience (Michel & Lau 2020). Unfortunately, there is reason to doubt that GWTs, HOTs, and IITs in particular champion markers that are truly unique to, or sufficient for, consciousness, as currently formulated. Settling this issue for each theory represents a massive research program in itself. However, note that recent studies have, for instance, supported the existence of unconscious information integration and helped to formalize certain subsequent hypotheses, such as the idea that conscious and unconscious processes operate over different (e.g., spatiotemporal, semantic) “windows of integration” (Fairve & Koch 2014, Hirschhorn et al. 2021, Mudrik et al. 2024). Considering the large volume of work demonstrating unconscious integration (see Brogaard et al. 2021), there are enough counterexamples to significantly decrease the reliability of ‘integrated information’, as formulated, as a unique marker of consciousness.

However, these results ought to inspire IIT loyalists to offer qualifications, reformulations, and precisifications of their candidate marker(s). Perhaps, for example, visual integration of spatiotemporal information over intervals greater that 100ms in neurotypical adult humans, is sufficient for experience, and therefore yields one marker of consciousness among many others that each support limited ranges of generalization (Faivre & Koch 2014).It is also important to recognize that IIT already adopts the idea that there will be a plurality of specific NCCs that correspond with different sorts of ‘integrated information’ (e.g., across the posterior “hot zone”, see Koch et al. 2016). This pluralism of NCCs is just beginning to be explicitly articulated and defended in the neurobiological literature (e.g., Malach 2021, He 2023). Similarly, GW and HO theories both imply that particular implementations of global broadcasting or metacognition will rely on a number of different specific neural mechanisms and their dynamic processes, albeit within the circumscribed neural regions emphasized by each theory (e.g., Cleeremans & Tallon-Baudry 2021). I argue similarly that acknowledging functional pluralism ought to inspire multiple sub-theories concerning differently qualified and formulated functions, perhaps within the broader categories of ‘information integration’, ‘global broadcasting’, and ‘metacognition’ that might come to count as genuine, reliable FCCs (Ludwig 2022). Each would generalize to a particular restricted scope of circumstances, relative to each different qualification of the broadly construed constructs that are put forth by the major theories as candidate markers.

Indeed, the progression towards increasingly precise hypotheses about structural and functional markers of consciousness has already produced a range of specific claims concerning neural and psychological phenomena that are thought to be truly unique to consciousness. One example of a very specifically proposed FCC is the visual integration of “apparent” motion information in humans, when the elements to be integrated are presented more than 100ms apart (Faivre & Koch 2014). Another relatively precise FCC hypothesis is that conscious processes are uniquely equipped to navigate a mnemonic “quality-space” that enables perceptual reality monitoring (Lau et. al 2022). Yet another is that experience facilitates “offline” model-based planning (Fleming & Michel forthcoming). In addition, surveys of the relevant empirical literature (e.g., Ludwig 2023, 2025) reveal a range of candidate markers of consciousness in certain “task-domains” like vision (e.g., greater spatiotemporal precision), emotion (e.g., capacities for regulation and inhibition), and social cognition (e.g., overriding social biases).

Finally, recall that Block’s (2023) analysis of infant colour perception informally suggests a clear candidate functional marker of consciousness. The hypothesis is that habituation to visual stimuli is unique to consciousness, at least in human infants; that is, this sort of habituation is a strong candidate for being an FCC. His informal discussion, moreover, cuts right to the core of how we might come to establish that such a functional capacity is indeed a reliablemarker of consciousness in at least a subset of conscious systems. He writes, “I have never heard of any evidence for decreasing or increasing level of interest as part of a person’s unconscious mental life” (2023, p. 422). The methodological implication is clear: the more evidence we have that habituation does not occur unconsciously, the more confident we can be that it is truly a marker of consciousness (perhaps across all systems with something akin to the primate visual system). And while the absence of evidence (e.g. of unconscious habituation) is not necessarily evidence of absence, carefully designed comparative task paradigms can continue to increase our inductive credence that a functional marker is unique to consciousness. In this way, the marker method provides a stable conceptual foundation for a robust science of consciousness.

3.2 The Marker Method Across the Sciences

It needs to be made explicit that the methodological practices and assumptions inherent in the so-called “marker method” are not unique to the study of conscious experience. Rather, they are extremely common across the sciences, and actually reflect fundamental and indispensable scientific principles. In other words, it is a mistake to treat the search for markers as one possible way (among many) of proceeding in the empirical study of consciousness, or as a contingent practice that could either be adopted or discarded based on our judgment of its capacity to deliver results (Andrews 2024). The moniker “the marker method” actually picks out an underlying logic that is at the very core of systematic empirical investigation. More precisely, it refers to a general strategy for studying target constructs—like those in psychology or economics—that are radically multiply realized (Fodor 1980).

Some constructs are useful for capturing generalizations at “higher” levels of explanation, precisely by abstracting away from “lower level” facts about particular manifestations of the construct. The construct “debt”, for example, supports crucial generalizations at the level of economic processes, but is not itself “observable” in any straightforward way, beyond the properties that “mark” its numerous particular instantiations. This is akin to other scientific constructs such as “organ”, “perception”, “metabolism”, or “life”. The basic investigative principles behind the marker approach are explicitly employed in an impressively wide range of different scientific domains. For instance, gravitational-wave effects are markers of black holes (Carr et al. 2024), certain hematological dynamics are markers of inflammation (Germolec 2018), and the biomass of phytoplankton can even serve a reliable marker of the impact of weather on certain ecosystems (Peierls et al. 2003).

Consider an example, however, within the cognitive sciences: “perception”. This is arguably a relatively stable and particularly useful construct for making sense of the operations of (at least some) psychological systems. The formal, empirically honed construct ‘perception’ continues to be fruitfully employed in a vast range of theoretical and empirical work. It is employed, for instance, in everything from theoretical debates concerning the structure of object representations (e.g. Quilty Dunn 2023), to valuable experimental and clinical research on pathologies like hemineglect and blindsight (Brogaard et al. 2021).

Block (2023) forcefully argues for a “joint in nature” between perceptual and cognitive processes, even gesturing towards the natural kind status of the construct ‘perception’. His systematic approach, though, begins precisely by identifying “markers of the perceptual and the cognitive” (Block, 2023, p. 61); in other words, a tentative list of various structural and functional features that belong uniquely to each construct. Block provides a fairly disparate list of “indicators” that seem to mark the presence of perceptual versus cognitive processing, including functional properties like susceptibility to adaptation, speed of computation, rivalry, and pop-out effects. Note that Block’s account is primarily focused on human visual perception, and we should probably expect the list of features that mark the construct ‘perception’ to become even more diverse as we explore other modalities, like proprioception or sonar. But crucially, despite being fruitfully employed in cognitive science, having a relatively clear set of markers, and even having a potential claim to natural kind status, the construct ‘perception’ is not grounded in a general theory that attempts to maximally generalize to all of its manifestations. In the end, despite the countless, immensely productive research programs working to understand different perceptual capacities, ‘perception’ itself is a term that lacks a comprehensive definition or general theory. The same is true of the empirical study of consciousness.

3.3 Markers and Theories of Consciousness

The prevailing assumption in contemporary consciousness research is that the explanatory value of the marker methodology entirely depends upon our ability to establish a secure, general theory of our target construct. The idea, again, is that without a general theory in place, there are no conceptual grounds for evaluating, justifying, or critiquing specific claims about NCCs and FCCs (Melloni et al. 2021, Andrews 2024).

Note first, however, that skepticism towards the reliability of the marker methodology in the absence of a secure general theory often follows merely from the recognition that current, specific candidate markers turn out to be insufficient, or not unique to consciousness. That is, many proposed markers are in fact present during unconscious processing; therefore, they are insufficient, and are unable to ground generalization and predication of the target of inquiry (e.g. Mudrik et al 2014). Andrews (2024), for example, infers from the fact that some current candidate markers (e.g. oxytocin-like neuropeptides) can be found in creatures who are generally assumed to lack the capacity for conscious experience (anatomically simple creatures like C. elegans), that the marker methodology is unreliable because of the absence of a secure general theory. But all this seems to warrant is the claim that we have not yet found reliable, or truly unique and broadly generalizable, markers of consciousness.

More importantly, it is not clear what role a general theory would play in helping to secure reliable ascriptions of consciousness. Recall that general theories are really making necessity claims, which are in principle unverifiable: we can never know conclusively if a structural-functional feature is present in every conscious experience that has ever and will ever exist. Still, we have good reason to expect exceptions to any claim that a structural and/or functional feature is maximally generalizable. This again seems especially plausible if we consider the complexity and diversity of our own experiences let alone other species’, the ongoing evolution of natural systems, and the constantly expanding capacities of AI systems. It is a safe bet that we will continue to discover different kinds of conscious experiences with different structural and functional features that cannot be captured by a single theory.

Thus, a general theory does not actually provide stable epistemic grounds for evaluating claims about our target of inquiry across different systems, primarily because they are built upon unverifiable hypotheses of necessity. Rather, contrary to the field’s prevailing methodological assumption, commitment to a general theory based on claims about necessary features can actually serve to limit the scope of consciousness research, in that it prioritizes and overemphasizes single (typically anthropocentric) markers, rather than encourage the continued search for a plurality of different markers derived from different manifestations of the target construct. The more markers we can establish that generalize to different ranges of conscious systems, the more evidential support we have for ascriptions of consciousness in an increasingly wide range of natural and artificial systems (Pennartz et al. 2019). The driving goal of consciousness research, therefore, should not be to give an account in terms of structures and functions that are necessary for consciousness (i.e., maximally generalizable) as most research programs assume (Michel & Lau 2020).

Not only do necessity claims warrant justification that is simply unattainable in theory and practice, necessity is not nearly as illuminating as sufficiency. It might turn out, for example, that something like a brain stem or a functioning heart is a necessary feature of consciousness (in humans or mammals). But because these features are also present when consciousness is not (i.e., they are not unique to consciousness), they are in fact unreliable in the central goal of distinguishing concrete cases of conscious and unconscious processing (Ludwig 2022). Identifying markers that are sufficient for, or unique to, consciousness, in contrast, is crucial to success in the field. Contemporary consciousness research therefore ought to be primarily dedicated to testing the uniqueness (or sufficiency) of various candidate markers of experience, under a broadly pluralistic framework.

If a candidate marker is indeed subsequently found to be preserved in creatures whose conscious status is controversial (like C. elegans), or for the sake of argument, a creature who has been determined in some way to lack any conscious experiences—that is, if the marker turns out to not be sufficient—we should lose confidence in that marker, and instead prioritize other candidates that might have a better chance of turning out to be truly sufficient for consciousness. Building confidence in the uniqueness of individual markers is how we move consciousness research forward. But pursuing a plurality of markers ultimately provides the widest possible scope of evidential support for the presence of the target property. Consider the range of “informal” markers we might use to determine if an individual is conscious in a real-world setting (e.g., post-injury): responsiveness to questioning or conversational capacity, complex emotional experiences (like terror or shock), pain, episodic memories, certain kinds of visual tracking, etc. Some might be more reliable than others, but the presence of several markers each with strong inductive support can certainly increase confidence in our ascriptions of consciousness.

The central point here is that the logic of the marker approach, and its prospects for success, does not require a general, all-encompassing theory of consciousness. In fact, general theories can actually serve to limit and restrict the scope of consciousness research by assuming that their candidate marker is the only one that indicates the presence of the target property. Further, even if a marker turns out to be truly unique to consciousness, the range of generalizations and predictions that it can support might be quite narrow in scope. Among other things, the obvious contemporary, anthropocentric origins of major theories on offer like GWTs and HOTs suggest that general theories of consciousness like these will be too narrow to account for all of the different kinds of conscious experiences that exist in the universe.

A pluralistic approach, in contrast, that does not commit to any one overarching theory, but instead encourages multiple theoretical frameworks to each search for unique, reliable markers that might expand the scope of generalization and prediction, seems to be our best option for accounting for the widest possible range of conscious systems. Developing different contributing research programs that represent unique approaches to the same target phenomenon seems analogous to building up multiple tools in a toolkit, each of which is useful for a different specific iteration of the same abstract category of task (e.g., Philips, Robertson, and Slotted screwdrivers all accomplish different iterations of the abstractly described goal of “screwing”). On the flipside, aiming towards a comprehensive theory is analogous to holding out hope for a single tool that can somehow apply to any specific iteration of the task (e.g., a single universal screwdriver that somehow fits every possible screw in existence).

4. Conclusions:

The Prospects of a General Theory of Consciousness

It remains unclear how we might successfully establish a general (“secure”, “comprehensive”, or “universal”) theory of consciousness, beyond the impossible task of capturing all of the unique or sufficient markers of consciousness that might exist in the universe, such that the theory is generalizable to every experience across all of space and time. Instead, an indefinitely wide array of distinct structural-functional features might be used to infer the presence of consciousness within a limited range of candidate systems. What, then, can we conclude about the search for a general theory?

First, the modest conclusion to be drawn here is that there are clear pragmatic reasons for moving away from the project of trying to establish a general theory of consciousness. This is reflected in the diversity of theoretical commitments that continue to emerge in the field, and the extent to which different theorists remain firmly entrenched in their preferred conceptual frameworks. Instead of being in competition, any particular productive theory might represent one reliable conceptual framework among many for understanding the target of inquiry. However, in practice, the attempt to establish a single, comprehensive theory of consciousness has narrowed the field’s explanatory scope by discouraging these diverse perspectives on the phenomenon. Theories of consciousness continue to proliferate, while very few are counted out as having nothing to offer contemporary consciousness research. I urge that we embrace such proliferation, precisely by committing to a pluralistic marker approach rather than a singular general theory approach.

We might also conclude that there are deep epistemic flaws in the general theory approach in the first place. Recall that general theories based on the structural and functional features of consciousness often bottom out as necessity claims; they reduce to claims that some feature is maximally generalizable. However, the unverifiability of a candidate marker’s claim to necessity renders any general theory claim at best speculative, and at worst epistemically vacuous. In this way, general theories cannot in principle provide the desired epistemic justification for ascribing consciousness across different systems, nor act as the ultimate arbiter of our claims about NCCs and FCCs. As it stands, this is a serious conceptual obstacle to the formulation of a general theory: a formal flaw in the primary explanatory goal at the heart of our scientific approach to consciousness. This ought to compel us to explore alternative methodological approaches, such as the pluralistic marker approach described above.

Finally, there is a stronger, more controversial conclusion that we might draw from this analysis: there is no such thing as a general theory of consciousness. That is, it is impossible in principle to ever formulate such a theory, even in maximally ideal epistemic conditions. Most researchers accept the pragmatic difficulties and epistemic flaws inherent in the search for a general theory of consciousness and will be open to alternative methodological approaches. However, optimism for a general theory remains inexplicably prevalent, and the denial that we could ever achieve this goal is where many researchers get off the proverbial bus. One persisting reason for the failure to accept this stronger conclusion seems to be that the science of consciousness is still relatively “young”, and so we should be patient that a comprehensive theory of consciousness will eventually be correctly formulated once and for all. On the contrary, significant support for the stronger thesis comes from the radical multiple realizability of consciousness, and moreover, the fact that some of our best candidates for being genuine FCCs and NCCs dissociate from one another across tasks, individuals, species, etc. For instance, in one system, consciousness might facilitate higher-order representation but not certain forms of emotional regulation, and vice versa. Even one such dissociation provides metaphysical reasons for doubting the existence of a single theory that can account for every kind of conscious experience.

In the end, there may not be a satisfying general explanation of what consciousness is as a feature of complex systems that can ground claims about its structural and functional elements. But “what is it?” questions are odd, and rarely guide empirical inquiry anyway, especially in cognitive science. We do not demand, for example, general theories of what perception or attention are; rather, the (sometimes radically) different structural and functional manifestations of these psychological capacities are the subject of their own robust and independent research programs, each of which sheds light on the overarching construct of interest. Similarly, instead of trying to constrain the flourishing field of consciousness research into the confines of a single theoretical framework, we should encourage a rich variety of perspectives that each provide their own particular, albeit limited, insight on target construct.

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Endnote

[1] Which, in consciousness research, may involve calibrating an experimental set up in some way to ensure an accurate comparison. For example, we often have to modify the objective properties of stimuli on unconscious trials, so that the internal signal strength of the perceptual target that the subject is being asked to detect is the same across conscious and unconscious trials (Peters et al. 2017).