1 Introduction

The author is the associate professor of the Budapest Business University. This study was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (project: BO/00143/23/2) and by the No. 138745 project of the Hungarian Scientific Research Fund. I am grateful to everyone who contributed to this article. In particular, I would like to say thank you to György Marosan, whose initial remarks on this topic in 2016 inspired me to start this project, and to Szilvia Hámor. I am also very grateful to Professor András Csillag for his careful and thorough comments on the biological and neuroscientific parts of this study. Furthermore, I am deeply indebted to my two anonymous reviewers for their numerous, detailed, and helpful remarks and suggestions. I also would like to express my gratitude for their comments to Todd Feinberg, Jon Mallatt, and Jeffrey Yoshimi.

We humans are conscious beings, meaning that we have conscious, lived, subjective experiences. We see, smell, and taste things in a conscious way, and we have painful and joyful experiences. It is most likely that we are not the only conscious living beings on this planet: in the light of the empirical evidence provided by their behaviour and functional apparatus (nervous system), it is very probable that at least some non-human animals are conscious to a certain degree. But which ones? And why? In this article, we endeavour to clarify certain elements of a phenomenologically based project whose main aim is to contribute to answering these questions.

The term ‘phenomenology’ here refers to the philosophical method employed by Edmund Husserl and his followers to analyse our first-person experiences (cf. e.g. Husserl, 1960, 1983; Moran, 2000). The classical authors of the phenomenological movement held the view that properly prepared and carefully conducted reflections on conscious, lived experiences and subjective existence as a whole could yield related necessary insights and disclose their fundamental features and laws. Two such insights are of particular interest to our enterprise. The first regards the holistic nature of our subjective existence. From this perspective, our conscious being should be conceived of as a concrete, coherent whole in which every particular subjective event, every segment, layer, and structure, is interrelated with the others. The second insight is that our existence is essentially embodied. In other words, every concrete subjective experience, as well as our entire existence, implicate that we are bodily creatures in the world. In this regard, it is also of the utmost importance that in Husserl’s opinion, the subjective and objective aspects of body, Leib and Körper, have a phenomenologically demonstrable a priori necessary connection.

In our enterprise, we will keep in mind first and foremost the Husserlian version of phenomenology, as elaborated in the publications and numerous manuscripts of Edmund Husserl; however, we will frequently refer to other authors of the movement, especially Merleau-Ponty, whose considerations on embodiment are particularly important to us. One central point of this project is that the necessary characteristics and relations of lived experiences disclosed by phenomenological reflection from a first-person perspective could orient empirical investigations from a third-person view regarding the external features of consciousness. Phenomenology could guide us regarding what to look for in the objective, physical world and where; in this way, it could help contribute to a scientific explanation of the origins of consciousness in the natural world.

One can, of course, always refer to the fallacies inherent in first-person perspective investigations – due to, for example, cognitive biases, unjustified presuppositions, perceptual mistakes, and hallucinations. Phenomenologists are intensely aware of such difficulties, which is why they ascribe tremendous importance to scientific discourse and intersubjective corrections of individual failures and errors (cf. Marosan, 2020a). The ultimate source of evidence and knowledge in phenomenology, however, is always the first-person perspective – every correction should be finally acknowledged as legitimate and justified from the phenomenologist’s own perspective (cf. Husserl, 1983, pp. 44–45).

The essential matter of this study is articulated into two main sections: A Phenomenological Study of the Minimal Mind and Its Embodiment (Section 2) and The Presumable Functional Architecture of the Minimal Mind (Section 3). In Section 2, we attempt to clarify the phenomenological foundations of this project, first and foremost relying upon Husserlian considerations. In Section 3, we take a closer look at certain empirical theories of consciousness and focus on the question of which features could form the basis for a natural scientific theory that is a promising candidate for a phenomenological approach, providing an adequate and plausible empirical correlate from a third-person perspective.

2 A phenomenological study on the minimal mind and its embodiment

This section, the first main part of the study, will treat the theoretical groundwork of first-person access to the minimal mind from a phenomenological perspective, which for us – as indicated in the introduction – first of all means the viewpoint of Husserlian phenomenology. Here we endeavour to show the most important structures of the minimal mind and various ways in which the results of first-person phenomenological reflections and investigations could be connected to empirical research.

After an initial clarification of the concept of the minimal mind, we will treat the phenomenological notion of subjective existence as a concrete, coherent, unified, and holistic mode of being-in-the-world, which is essentially embodied. The microanalysis of this embodiment will show that its subjective and objective moments are strongly intertwined and that the overall subjective aspect of the body, Leib, cannot be separated from its objective aspect, Körper. This leads us to a conception that we call the embodied manifestation thesis, according to which all subjective capabilities, content, and events necessarily refer to an objective bodily structure or process that carries and realizes the former.

These considerations enable us to provide a more elaborate phenomenological conception of the minimal mind, that is, a partly hypothetical reconstruction of the subjective mental life and architecture of at least minimally conscious subjects – such as the minds of, eventually, lower-level invertebrate animals and human embryos. The holistic conception of subjective existence, along with the embodied manifestation thesis, result in the idea that to a minimal mind, there corresponds a set of objective bodily structures that makes this mind possible, activates it, and allows it to function. We will refer to the idea that the minimal mind implies a minimal set of subjective, mental, and correlated objective bodily conditions as the minimal context thesis. A systematic phenomenology of the minimal mind would be a methodologically conscious exploration of this minimal context.

These developments enable us to proceed to the thesis of Section 3, namely that based upon the principles of the embodied manifestation thesis and minimal context thesis, we could articulate an assumption regarding which of the currently existing empirical models of consciousness is best supported by such a phenomenologically articulated theory of minimal mind, which we present in this section.

2.1 An initial notion of the minimal mind: conceptual clarifications

Consciousness has many different forms, manifestations, and layers. Self-consciousness, rationality, and linguistically shaped abstract thoughts in human beings represent its highest level. We, however, are seeking the lowest, most fundamental form and level of consciousness, which is subjective, conscious, sensuous experience – such as feeling pain, joy, or having a visual experience. Consciousness, above all, means being conscious of something, which, in this context, at the deepest level of experience, is sensory, perceptual content or givenness. Moreover, consciousness, especially at the level of sensuous experience and sensory perception, necessarily possesses a particular phenomenal and qualitative character (Nagel, 1974; Chalmers, 1995, 1996; Gallagher & Zahavi, 2008, pp. 107–116). Experiences such as seeing the sunrise, smelling a rose, tasting a coffee, or touching the smooth surface of a silk robe each has a unique qualitative feature.

Sensory data can have different grades of intensity. A sound can be louder or softer. These data do not stand separately on their own; rather, they relate to one another and comprise the parts of a larger, coherent, organic whole, which also represents the attributes of an objective space in the form of a perceptual field. Our attention, guided by our temporary or general interests, always articulates the perceptual field, highlights patterns and forms in the latter, and arranges it according to figure-and-background and foreground-and-background relations. Perception (and, correlatively, the perceptual field) has a focal point and marginal parts, which also implies that in the perceptual field or stream, not all phenomenal content is necessarily directly, explicitly, and clearly accessed at the same time (Block, 1995). Certain mental content might be stuck below the surface of clear consciousness.

The general sensorimotor and cognitive apparatus of living beings has three fundamental subsystems which, after attaining a certain point of complexity and grade of organization, lead to phenomenally conscious states and acts. The exteroceptive system represents the external environment of the organism. Interoception represents the states and changes of the body. The affective-evaluative system furnishes bodily and sensory-perceptual states and events with a certain valence: it defines whether an event or a state of affairs is actually or presumably good or bad for the subject; it bestows a peculiarly positive or negative affective character (most generally, pain or joy, punishment or reward) to bodily or sensory-perceptual reports of certain states and events (e.g. Feinberg & Mallatt, 2016; Ginsburg & Jablonka, 2019). Finally, we should also add that a concrete perceptual experience – from a phenomenological point of view – necessarily has a temporal character. In other words, a perception cannot be concrete unless we retain its recently passed phases (this retained or fresh memory is called ‘retention’ by Husserl) and anticipate what might come (a short-run or immediate anticipation; in Husserl’s terminology, ‘protention’) (Husserl, 1991, 2001).

In contrast to consciousness, which mostly refers to individual conscious acts and content, mind is a term for the entire mental sphere; it embraces all mental acts and content, including those that are conscious, subconscious, and unconscious. In our view, to the ‘minimal mind’ pertains the essential capacity of having phenomenally conscious, subjective experiences. We believe that we cannot consider a living being conscious in the strict sense (i.e. we cannot legitimately attribute a mental sphere to it in the narrow sense) if it lacks the capability of clear, explicit, phenomenal consciousness. In the following subsection, we take a closer look at the general features of the organization of the minimal mind through the lenses of phenomenological reflection.

2.2 The totality of subjective existence as a concrete way of being-in-the-world

The classical authors of phenomenological philosophy and philosophical anthropology have all agreed that subjectivity and existence in the case of humans, as well as animals, should be conceived of as a coherent, unified, and organic system of structures within which every moment and capability has a definite place and is interrelated with the others. For Husserl, it was the operation of phenomenological reflection in particular whose main aim was to unfold the general features and microstructure of the organic system of subjective, conscious life (cf. e.g. Husserl, 1983, p. 174). Husserl believed that proper and meticulous application of the phenomenological method could reveal to us the a priori relations of different phenomena, namely, those of consciousness and the relationship of consciousness to body and world (Husserl, 1960, 1983). Husserl further claimed that – especially from an empirical regard and in an objectifying manner – we should conceive of the entire mental sphere as soul (Husserl, 1989a).

In Husserl’s opinion, the soul does not stand on its own, separated from the body and our concrete, practical relation to the world, but just the opposite. In his eyes, the entire soul is present in every bodily movement and gesture, in every segment of our worldly praxis (cf. Husserl, 1973a, pp. 69–70). For him, the different mental capabilities have the function of helping us to get along in the world; they connect the subject – the ego – to the world. The three fundamental modes of sensuous, perceptual consciousness mentioned in the previous section – exteroception, interoception, and affective-evaluative consciousness – have exactly this purpose of enabling us to live our lives; for animals, this means basically to survive and reproduce, and for humans, to achieve higher, culturally shaped goals as well. In Husserl’s interpretation, the soul is a complex and coherent organization of mental capabilities which represents the internal, subjective aspect of a concrete – and from an empirical viewpoint, evolutionarily evolved – way of life, which is the inner side of our being-in-the-world.Footnote 2

In the next subsection, Husserl’s emphasis on the essential embodiment of soul and subjectivity is of crucial importance. According to Husserl, every segment of subjectivity, all mental capabilities, and their actual realization is fundamentally characterized by the fact that we are bodily beings in a physical world (cf. e.g. Zahavi, 1994, 2003; Behnke, 2011; Moran, 2015). Accordingly, he holds that the bodily aspect of existence is involved or indicated in every subjective capacity, in all mental states, events, and actions. Embodiment is the condition of possibility for our practical activity in the world, and the fuller, more concrete meaning of our subjective existence can only unfold with a special regard to it. In the following subsection, we take a closer look at Husserl’s understanding of soul and body and, more specifically, his interpretation of the subjective and objective aspects of body, Leib and Körper.

2.3 Husserl’s conception of the constitutive connection between Leib and Körper

In this subsection, we attempt to show that the classical phenomenological conceptions of embodiment that we find in Husserl and Merleau-Ponty can serve as parts of theoretical foundations for phenomenologically based but empirically related research on the emergence of consciousness. We will try to demonstrate that an accurate and intersubjectively embedded analysis of the body yields what we call the ‘embodied manifestation thesis’, according to which every subjective capacity, state, or event refers to an objective correlate in the body as a bodily capacity, state, or event, and they are connected in an a priori necessary way. We should emphasize that the embodied manifestation thesis is not an identity thesis. ‘Correlation’ is not identity. On the contrary, we would like to emphasize that according to the standpoint that we adopt, subjectivity has certain irreducible features – most importantly, its qualitative character.

For a proper understanding of Husserl’s conception of embodiment, we should first examine more closely two fundamental notions of his philosophy: constitution and phenomenological reduction. Regarding the former, Husserl refers to the a priori laws and features of appearance with the term ‘constitution’ (cf. e.g. Sokolowski, 1970; Moran, 2000, pp. 164–166; Zahavi, 2003, pp. 72–77). He says that a particular thing is somehow ‘constituted’ to specifically highlight the a priori fashion of its appearance. For him, things cannot appear in an entirely arbitrary way; instead, every appearance is subject to certain a priori laws. To a concrete perception, for example, according to Husserl, necessarily pertain recently passed phases in the form of retentions, along with certain anticipatory tendencies as protentions (Husserl, 1991, 2001), just as the appearance of the front side of a three-dimensional object inevitably indicates its unseen parts. As we shall soon see, he also assumes such a necessary, constitutive connection between soul and body and the subjective and objective sides of our body.

As regards the latter notion, Husserl elaborated a methodologically sophisticated application of phenomenological reflection that he called phenomenological reduction (cf. Husserl, 1960, 1983). This refers to the philosopher suspending or ‘bracketing’ every belief, assumption, and presupposition that does not rest upon immediate or immediately accessible experience (Husserl, 1983, pp. 44–45). What truly matters for the philosopher regarding phenomenological reduction is not the question of whether a subjectively appearing thing exists in reality, outside her mind, but of how this thing appears and what objective sense (gegenständlicher Sinn) it carries. Reduction, in his interpretation, leads us back to a sphere of pure appearances and a complex web of objective meanings whose particular content was made concrete and specific by this very context. In this framework, ‘transcendence’ and ‘being transcendent’ are such objective meanings. In Husserl’s eyes, one should examine, through phenomenology, which phenomena exhibit the meaning of ‘transcendence’ or ‘transcendent’ and how.

Concerning phenomenological reduction, two crucial issues are the status and results of the empirical sciences. Theoretically, with this reduction, the phenomenologist must exclude all information neither acquired through the phenomenological method nor based upon phenomenologically clarified immediate or immediately accessible experience (i.e. every piece of knowledge derived from non-phenomenological empirical research). Husserl, however, has a solution for this in what he calls ‘double’ or ‘intersubjective’ reduction, a specified and extended version of phenomenological reduction (Husserl, 1973a, pp. 177–179, 188–191). This specification of the phenomenological method makes it possible for the phenomenologist to regain the results and assumptions of the empirical sciences for phenomenological investigations as complexes of meanings of limited phenomenological validity, meaning that they require further phenomenological supervision and clarification. Husserl uses this method extensively in the second and third books of Ideas (1980, 1989a) and in other works.

This is the overall context of Husserl’s theory of embodiment, which entails an a priori necessary connection between soul and body (1989b, pp. 11–12), internally experienced (Leib) and externally appearing (Körper) aspects of the body, and finally, the immanent and transcendent sides of the body, namely, the body as it appears and as a physical, mind-transcendent entity in nature (cf. e.g. Husserl, 1973a, p. 75, 1973b, p. 263; Zahavi, 1994, 2003). A careful and thorough phenomenological study of the bodily nature of experience, according to him, could shed light on the exact manner in which soul and body, internal and external, and immanent and transcendent moments of the body are connected to each other in an a priori way.

From the inside, internally, the body, as Leib, manifests itself as a constant stream of proprioceptive (experiences of bodily states, processes), kinaesthetic (experiences of bodily movements), and affective feelings, articulated in a well-organized system. The microanalysis of these internal bodily experiences reveals intrinsic indications referring to externally appearing and transcendent moments of the body (as Körper) to which the former are necessarily linked. In Husserl’s interpretation, the flow of bodily experiences and the intimate weave of internal and external moments of the body make manifest the inseparable unity of Leib and Körper: the fact that they are two sides of one and the same unity (cf. e.g. Husserl, 1973a, pp. 262–263, 1973b, pp. 414, 462, 1977, pp. 150–151).

In Husserl’s theory of embodiment, the notion of organ has a special role in creating this unity; the body, also in a phenomenological regard, could be thematized as a compact, coherent unity of organs (Husserl, 1997; Claesges, 1965). An organ is a bodily part with a particular function of making possible and realizing certain moments of one’s being-in-the-world. The functioning of our organs, just like the body as a whole, has internal and external, immanent and transcendent aspects. We have internal (proprioceptive, kinaesthetic, affective) experiences regarding the functioning of – at least some of – our organs; some can be experienced externally (we can see or touch them); we can find certain ways to experience others (think of a doctor who – if necessary – could operate on herself); and we can also experience the functional achievements or results of those organs (e.g. vision as the result of the proper functioning of our eyes and the wider visual system of the body).

Specifically, the sense organs have the function of connecting us to the world in specific ways. If they malfunction, the correlative form of sensible experience cannot be adequately realized. In Thing and Space (1997) and other works, Husserl devotes detailed, microscopic analyses to the internal, external, and functionalFootnote 3 aspects of the experience of sense organs, and he emphasizes how strongly and intimately these aspects are interrelated. Our embodiment is through and through indicated in the functioning of our sense organs. Accordingly, the functional achievements and realizations of these organs are always accompanied by internal (proprioceptive, kinaesthetic, and affective) bodily experiences, and our entire bodily being as a whole is always implicated in them. The sense organs – along with the particular sensory system (e.g. the eye and the visual system of the body) – realize a perceptual field whose particular realization is dependent on the actual position and movement of the particular sense organ in question, on the one hand, and on the momentary position and movement of our entire body on the other. From the fundamentally embodied character of subjectivity in general, and perception in particular, it follows that every change in the perceptual field refers to a change in the bodily basis which realizes it.

Of course, we can regard a certain type of perceptual field (e.g. the visual or tactile field) on its own, separated from our entire bodily existence and the particular sense organ (eye, ear, etc.) that realizes it. From the viewpoint of the phenomenological theory of constitution, however, this regard would be abstract. Such a treatment would be isolated from the complex web of meanings disclosed by phenomenological reduction. If we separate the perceptual field from its bodily basis and the sensory organs that realize it, we neglect its fuller, concrete constitutive meaning. In this case, we cannot explain phenomenologically why this perceptual field changes in strong correlation with changes in the functioning and position of sensory organs and our whole body.Footnote 4

2.4 The constitutive and ontological relationship between soul and body: the embodied manifestation thesis

Husserl believed that there exists a particular organ specifically responsible for the body–soul connection that enables the functional realization of all our sense organs. He spoke of this organ, namely, the nervous system, as the ‘central organ’ of our body (Husserl, 1989a, p. 304). Husserl posited a functional connection between mind and body, and mind and nervous system in particular. From a Husserlian perspective, it is the nervous system that establishes the ‘psychophysical dependency’ of the soul and body, somehow connecting these two realms (Husserl, 1989a, pp. 161–165, 302–310, 2020, pp. 47–66; Yoshimi, 2010). As we might expect, Husserl’s viewpoint here is anything but naïve. He was keenly aware that the nervous system belongs to the transcendent aspect of our body and that empirical science informs us about its proper nature and functioning. Nevertheless, he considered that the knowledge of the nervous system that natural science provides us is phenomenologically relevant. It has particular significance for a phenomenological theory concerning the constitution of the body, provided that we are careful to use this empirical knowledge in the phenomenological attitude.

For Husserl, the relationships between Leib, Körper, the nervous system, and the soul are quite complicated. He very clearly argued that Leib and Körper constitute a coherent unity, in which these two aspects – the immanent and transcendent sides of the body – belong together a priori. Husserl even frequently used the term Leibkörper to express their unity (see e.g. Husserl, 1973c, pp. 26-29, 246-258, 278, 282-287, 297-302; see also Wehrle, 2020).Footnote 5 How does this Leibkörper-unity, together with the nervous system, affect our soul, our subjectivity? Regarding our lower mental faculties, sensations (Empfindungen) and the purely sensible aspect of perception, Husserl is again completely clear: every change in our experiential field refers back to bodily changes in our sense organs and nervous system. Sensations, in his interpretation, are totally dependent on our bodily functioning; they correlate to bodily states, changes, and processes (Husserl, 1989a,Footnote 62020Footnote 7). Husserl assumed a constitutive connection between the functioning of the sense organs and the nervous system on the one hand, and the emergence of sensations on the other. In his view, we cannot grasp the concrete phenomenological meaning of the emergence of a sensation by abstracting from the concrete bodily functioning to which it refers.

As regards the relationship between higher mental faculties (e.g. fantasy, image-consciousness, or thought) and the entire mental sphere as such (the soul) on the one hand, and our body and its nervous system on the other, Husserl assumed the partial dependency of the soul on the body (Husserl, 1989a, pp. 302–310; Yoshimi, 2010). More precisely, he held that the body and the soul have a fundamentally empirical and contingent relationship, although he did not conceive of this relationship as entirely contingent, claiming that it also has certain a priori necessary features.Footnote 8 The soul needs a body through which it can connect to the world, and the way in which this connection is achieved is not arbitrary but rather determined by the peculiarities of the body. Regarding specific mental phenomena, Husserl hypothesized that some of them might not have a physical basis or carrier and that experimental psychology has the duty and authority to decide which have a bodily basis and which do not (Husserl, 1989a).Footnote 9

Husserl’s overall conception of the relationship between mind and body has a further strongly related peculiarity that should be noted. Namely, he emphatically denied that their connection could be characterized in terms of causality. In other words, he rejected that the soul could have a causal effect on the body and nature in general (Husserl, 1989a).Footnote 10 He spoke of motivation as ‘the fundamental lawfulness of spiritual life’ (Husserl, 1989a, p. 252), and standing in opposition is causality, the fundamental law of nature. He claimed that the order of the will is ‘completely different’ than the order of the nervous system, and he even added that ‘the nervous system has no effect on the mental [sphere]’ (Husserl, 2020, p. 64). We should interpret these words carefully.

First, it should be emphasized that Husserl does not assert that there is no interaction of any kind between the mental and physical-bodily spheres. He explicitly and passionately rejected what we call epiphenomenalism as ‘absurd’ psychophysical parallelism (e.g. Husserl, 1980, p. 15, 1989a, pp. 302–308). He only asserted that these two spheres are governed by completely different types of laws. We can describe physical causality with exact laws, whereas the psychological sphere, in his view, lacks this exactness. I interpret this approach to have two implications. First, the decisions and actions of a subject can never be precisely predicted; rather, a person can certainly act to initiate a completely new causal line without causal antecedents in the realm of nature (Husserl, 2020).Footnote 11

For Husserl, the necessary relationship of Leib and Körper and the – at least partially – necessary relationship between soul and bodyFootnote 12 rest upon an order of appearances and the a priori features of this order. In his opinion, this a priori relationship can be conceptualized, first of all, between the lower levels of the soul (our purely sensible mental capabilities) and the body. I believe, however, that this necessary connection might also be extended to the higher levels and abilities of the mental sphere. Later, Merleau-Ponty dedicated incredibly nuanced lifelong efforts to show that every manifestation of mental ability, content, and achievement is essentially embodied, including activities of memory, imagination, and conceptual thought (1967, 1968, 2002). Merleau-Ponty adopted an ontological stance concerning the mind-body relationship; accordingly, in his interpretation, the a priori features of the relationship between consciousness and the body are rooted in the order of Being. This conception became an empirically related, concrete research project in later phenomenologist proponents of embodied cognition, who attempted to show how every moment of conscious life is shaped and formed through embodiment, thus leading the mind–body problem back to the body–body (Leib-Körper) problem (cf. e.g. Varela et al., 1991; Thompson, 2007; Gallagher & Zahavi, 2008; Fuchs, 2018).

What we have called the ‘embodied manifestation thesis’ is a logical consequence of all the considerations treated in this section. This requires a partial revision of Husserl’s conception of embodiment, from the perspective of Merleau-Ponty and representatives of the school of embodied cognition. Husserl, as we saw, conceived of the soul as a ‘mixed reality’ (1989a)Footnote 13 that is intimately bound up with the body but that also has content that does not or – at least – might not have a physical, bodily basis (1989a, p. 308). To the best of this researcher’s knowledge, no empirical study has yet found any single mental event – following a scientifically verified and documented protocol – which lacks a physical, bodily basis. Moreover, based on existing empirical research on the psychophysical connection of mind and body, no mental event or capacity has been found to exist independent of the body.Footnote 14 In short, as science stands today, no mental phenomenon is thought to exist independent of the body.

If we accept Husserl’s contention that the ego necessarily and in an a priori fashion constitutes herself as an embodied being in the world (Husserl, 2008, pp. 251–258,Footnote 152012Footnote 16), and if we also accept the considerations regarding the strong embodiment of the entire mental sphere found in Merleau-Ponty and the school of embodied cognition, we can venture to posit the ‘embodied manifestation thesis’, according to which every capability and instance of mental content refers back in a necessary way to a physical-bodily carrier, and there is a necessary connection between them, which, from the viewpoint of the phenomenological theory of constitution, could also be considered a priori. In my view, this would represent a mere extension of Husserl’s own conception of the constitutive connection of mind and body, achieved by incorporating – following Merleau-Ponty and certain representatives of the embodied cognition school – the necessary and strong embodiment of higher (and all) mental faculties.

The comprehensive bodily basis that carries all mental content and capabilities could be conceived of as a ‘functional skeleton’ whose task is to channel the concrete conscious aspect of a living being into the world. The next subsection represents and attempt to show the consequent implications regarding the minimal mind, resulting in what could be referred to as the ‘minimal context thesis’. The minimal mind, as we will see, also has an underlying ‘functional skeleton’, which is part of this ‘minimal context’.

2.5 A phenomenologically elaborated conception of the minimal mind: the minimal context thesis

Since he started dealing with the problem of intersubjectivity around 1905 (Husserl, 1973a), Husserl dedicated thorough and careful analyses to the problem of the animal mind and lower forms of consciousness (including the presumable subjectivity of early infants and possibly embryos) in particular (cf. Vergani, 2021; Marosan, 2020a, b). Husserl approached lower levels of consciousness in two general ways: externally, based upon empathy regarding other subjects, and internally via a deconstructive-reconstructive (Abbau-Aufbau) method established through phenomenological reflection on one’s own consciousness. The problem of embodiment, nevertheless, plays a crucial role in these investigations on lower-level subjects. Such phenomenological investigations could lay the foundations for empirically related research regarding the ontogenetic and phylogenetic emergence of consciousness in the natural world.

As mentioned in the previous subsection, Husserl believed that if I experience a body similar to mine in visual, behavioural, and functional (bodily structure) regards, I am capable of constituting it as the lived body (Leib) of another subjective, conscious person (e.g. Husserl, 1960). For him, the experience of this similarity triggers a passively intentional process that he calls ‘pairing association’, which enables me to constitute the body of the other person as an analogue of my body, a subjectively lived body, in an a priori fashion (Husserl, 1960, pp. 80–81, 112–113). Empathy, which is a composite and founded type of intentionality that presents the other subject to me as a conscious, living, feeling, sensitive person, is based upon this pairing association (to this, see also Jardine, 2022). In Husserl’s interpretation, empathy is not restricted to human intersubjective relations but is also possible amongst different species. In other words, I can also empathize with animals, and animals can empathize with each other too.

From the perspective of an adult human person, in Husserl’s view, animals and early infants (embryos) could be thematized as anomalous subjects (cf. Ciocan, 2017), meaning they might be very different from us; nevertheless, they still have rudimentary subjective experiences and some sort of lower-level concrete, conscious existence. Husserl assumes that we have at least two reasons to attribute consciousness in the strict sense to animals and early infants (embryos). First, they sufficiently resemble us in functional, bodily, and behavioural regards to intelligibly constitute them as conscious beings. They are similar enough to us to motivate a phenomenologically grounded empathy in us towards them. Second, they have a nervous system, which is – for Husserl – a phenomenologically accessible subsystem of the body and a peculiar organ which is inevitable for the activation of consciousness and realization the psychophysical dependency of the soul on the body.

Though Husserl sometimes plays with the thought that living beings below the level of animals, such as plants and unicellular organisms, might have consciousness (cf. Lee, 1993, pp. 225–230), he generally deems them too far from us in functional, bodily, and behavioural regards to conceive of them as creatures with concrete consciousness, in the strict sense, or to give rise to a phenomenologically motivated empathy in us (Husserl, 1980, pp. 8–9).Footnote 17 He presumes that the presence of a nervous system in animals also indicates the boundaries of phenomenologically legitimate empathy and intelligible constitution of concrete conscious subjects. In this way, his recurring example of a minimal subject with a concrete minimal mind is the jellyfish (Qualle), with its decentralized nervous system (Husserl, 1973a, pp. 112–119, 2003, p. 136, 2020, p. 52).Footnote 18 But what might such a minimal subject look like ‘from the inside’ according to Husserl?

His other, ‘internal’ way of apprehending lower minds is the deconstructive-reconstructive approach. This method implies that the philosopher reflects on her own consciousness and attempts to abstract from the higher layers (e.g. clear self-consciousness and conceptual thought), excavate the lower, purely sensible layers of subjectivity characteristic of lower-level subjects, and focus on the microstructure of these layers. In Husserl’s interpretation – as seen in Subsection 2.2 – conscious existence must be concrete on every level – a coherent, specific mode of being-in-the-world, even on the level of a minimal subject. The total sphere of subjectivity of such a being should consist of a minimal set of conscious structures and capabilities which make possible a minimal concrete subjective being-in-the-world. This set should be further defined by thoroughgoing embodiment. But what exactly would be the main elements of such a minimal set?

In Husserl’s view, such a simple or minimal subject (an animal of lower complexity or a human embryo) simultaneously represents the highest level of conscious (wakeful) passivity and the lowest level of activity. He presumes that even the lowest level of life should be characterized by a certain grade of activity (cf. Marosan, 2022b); however, the case of a minimal subject represents possibly the lowest degree of conscious activity. In this regard, Husserl’s concept of instinctive intentionality is of fundamental importance (cf. e.g. Husserl, 2006, 2014, pp. 83–136; Lee, 1993). Husserl rigorously distinguishes the phenomenological notion of instinct from its naturalistic and biological conception. For him, instinct in the phenomenological sense refers to a passive, teleological directedness in the consciousness: an entirely or predominantly passive form of constitution. Instinctive intentionality articulates and guides the formation of our fields of perception, sensation, and action, motivating us to achieve certain ends, though not informing us how. It indicates certain directions, makes us reach out gropingly, triggers half-automatic sequences of actions, and urges experimentation to find ways to realize somehow those indefinite goals that it sets us. What, from an empirical regard, appear as instincts of individual and generic self-preservation, from a phenomenological point of view, could be treated as instinctive ways of constitution of the ego to preserve certain forms of self-constitution, namely, self-constitution as a physical being at the lower levels and as a cultural being at the higher ones.

The minimal subject experiences a flow of sensations articulated by this instinctive intentionality. This flow basically represents the external environment in a very rudimentary way. The field of sensory perceptions already has more or less salient patterns and is articulated by the instinctively driven attention of the subject into relations of foreground and background. The stream of exteroceptive sensations is accompanied by a flux of affective feelings, positive or negative evaluative experiences, and experiences that continuously report the current state of the body to the ego, namely, kinaesthetic and proprioceptive experiences. These exteroceptive, affective-evaluative, and interoceptive ways of functioning (seen in Subsection 2.2) form a concrete, coherent, single weave and together contribute to the constitution of a concrete subjective being-in-the-world. Further, these sensations already have a certain grading: they might be more or less intensive. Therefore, a minimal mind implies a minimal scale for the capacity of conscious sensations and experiences.

Husserl also holds that subjectivity, even at the lowest level, has an essentially and necessarily temporal character. No sensation can be concrete unless connected with primary, short-term memory and anticipation – in Husserl’s vocabulary, retention and protention. But the minimal mind, for Husserl, should also have a minimal range of long-term memory and anticipation; otherwise, learning would be impossible. Husserl claims that learning and motivation based upon memory are both indispensable to enable a concrete way of life in the world (e.g. Husserl, 1989a).Footnote 19 All of these subjective, conscious faculties (mentioned in the previous subsection) are fundamentally embodied and – in an extended version of Husserl’s theory of bodily self-constitution about which we wrote in the previous subsection – refer to a bodily basis as their carrier and realizer.

What we called the ‘minimal context thesis’ is a direct consequence of these considerations. It means that a minimal subject is embedded into a minimal context, which is a composite set of subjective and objective conditions and structures that make a concrete and minimally but continuously and clearly conscious way of life possible. It is a minimal set of capabilities and actual performances of exteroceptive, interoceptive, and affective-evaluative subjective experiences, along with the bodily foundations that carry and realize them, which – based upon discussion in the previous subsection – should be conceived of as a minimal functional architecture. Every body part belongs to this functional architecture, which is directly responsible for the realization of consciousness. From an empirical – or phenomenologically revised empirical – perspective, such parts mostly belong to the nervous system since no stimulus can be conscious unless it enters the central nervous system.

The insights of this part of our study have immediate empirical implications. The minimal functional architecture is represented by the functional arrangement and achievements of a neurological and neuroanatomical set which can realize the minimal mind.Footnote 20 This structural set must reflect a concrete conscious mode of being-in-the-world, which, at the lowest level, is the conscious life of a minimal subject. If we trust the results of the phenomenological method and not only accept the necessary connection between the subjective and objective sides of the body (which is the embodied manifestation thesis) but also accept that the minimal functional architecture reflects a concrete, minimally conscious being-in-the-world (which is the implication of the minimal context thesis), then we must also accept the fact that there are certain empirical and, more specifically, neurological models of consciousness more endorsed and supported by first-person perspective phenomenological research, and there are others which are less consistent with the results of a phenomenological approach.

That is, from a phenomenological perspective, the fundamental structure of the minimal mind as it appears ‘from the inside’ under phenomenological reflection must encompass in its structural aspects the presumed functional architecture of the bodily realizer of consciousness as it appears ‘from the outside’. Next, we try to find the best-fitting neurological model for this phenomenological conception, which is also verifiable by phenomenologically founded, first-person perspective research.

Earlier, especially in Subsection 2.4, we made several attempts to show the particular importance of the nervous system from a phenomenological regard.

3 The presumable functional architecture of the minimal mind

According to the considerations of Section 2, the phenomenological reflections on the minimal mind and the relationship between mind and body (Leib and Körper) have certain serious and inevitable consequences for empirical research into the origins of consciousness in the natural world. If we accept the results of Husserl’s investigations on the embodied nature of conscious experience and the minimal mind (as we slightly modified in the previous section), we must also accept that concrete consciousness as a whole and individual conscious experiences necessarily refer to a bodily basis as their carrier and realizer.Footnote 21

In the natural world, a specialized functional apparatus connects the organism to its environment and helps it to receive, gather, and process information about its surroundings. To be sure, before multicellular animals with neurons, other creatures (e.g. fungi, plants, and unicellular organisms) also possessed non-neural ways of carrying out these functions. In animals, nervous systems appeared as specialized subsystems whose central function was to process and integrate sensorimotor, affective-evaluative, and cognitive information; they proved to be extremely effective tools (cf. e.g. Ginsburg & Jablonka, 2019, pp. 251–273). Based on current knowledge regarding the empirical features and indicators of consciousness, it seems almost certainly activated and realized by certain neural circuits in the human – and in certain animals, the non-human – brain. In this section, we aim to identify which currently existing neural model of consciousness is endorsed by an ‘internal’ phenomenological approach as perhaps the most appropriate.

Though there are researchers who believe that consciousness is fundamentally illusory and that self-reflection could easily lead us astray (e.g. Daniel Dennett or Susan Blackmore), Husserl and his followers – the latter to this very day – strongly believe that methodologically careful reflections can still yield apodictically true insights into consciousness. Intersubjective discourse could correct eventual errors of individually conducted self-reflection. The concreteness of conscious existence, even on the minimal level, and the intrinsic embodiment of conscious experience are rather consensual insights in the phenomenological tradition. These ideas have considerable consequences for phenomenologically oriented empirical research on consciousness.

Proponents of embodied cognition, in particular, periodically emphasize that a nervous system is always embedded in a wider context and is not viable on its own, separated from this context (Gallagher & Zahavi, 2008; Cosmelli & Thompson, 2010; Fuchs, 2018), as the non-neural parts of the body participate in concrete realizations of consciousness in a fundamental way. However, it is also generally accepted that no stimulus can become conscious until entering the nervous system. Therefore, we first focus on the presumable neural basis of the minimal mind as its structural and functional foundation. Based upon the results of the previous section, we suppose that there must be a minimal neural structure that forms the functional basis of the minimal mind. We believe that the assumed neural structure or structural set must enable a concrete, coherent, conscious way of life as a whole.

3.1 Which natural scientific theory of consciousness is best suited to a phenomenological approach?

Consciousness has certain characteristic general and intrinsic features which are independent from its particular bodily basis. It also has a certain qualitative character in general (i.e. there is something to live through a peculiar experience, e.g. to taste a certain coffee). It is always related to or directed at something: certain aspects, elements, or events of the internal or external environment (intentional relatedness). Last, but not least, we also should attribute a certain self-relatedness or self-manifestation to consciousness (Husserl, 1991, p. 83; Gallagher & Zahavi, 2008; Zahavi, 2017, p. 198). This means we are always implicitly aware of consciousness functioning and the peculiar way it functions. For example, if we lose our sight, or if our normal visual experience suddenly changes drastically for some reason, we are usually immediately aware of it. Phenomenological reflection informs us about these general features of consciousness.

There are other, specific characteristics of consciousness, however, which refer to the bodily basis and its peculiarities. The different structures and capabilities must form a concrete sort of consciousness reflecting a concrete way of being-in-the-world (Subsection 2.2). This must refer to a certain set of concrete bodily structures. The concrete, specific capabilities and their achievements, the conscious mental states, content, and processes, as well as their internal relations, however, always refer to a concrete bodily basis, state, or process that realizes them (Subsection 2.3). From a phenomenological perspective, an empirical theory and model of consciousness must therefore be, in the end, supported by the findings of phenomenological reflection. In praxis, this means that a phenomenologically grounded theory must first meet all of the following four criteria. (1) Consciousness, as a conscious aspect of a concrete way of being-in-the-world, must be concrete. (2) Consciousness must be strongly embodied. (3) A minimal mind, as a conscious way of existing on the minimal level, implies a minimal set of bodily structures (a ‘core realizer’) that realizes this (Chalmers, 2000; Block, 2005; Cosmelli & Thompson, 2010). We assume that this minimal structure is primarily a certain neural pathway or architecture. (4) Such a theory, in the end, must be verifiable from the first-person perspective – from the perspective of an adult human person – which is a point of departure for phenomenological investigations.

A phenomenologically based framework for empirical research regarding the origins of consciousness requires one more presupposition: the principle of phenomenologically legitimate maximal extensibility of the capability of consciousness.Footnote 22 This principle is rooted in the nature of phenomenological investigations, according to which the phenomenologist should seek the limits of phenomenality: the boundaries of the realm of a particular type of phenomenon.Footnote 23 This implies that the answer to the question of which living beings are possibly conscious should not be trivial or all too convenient on the one hand; however, on the other hand, the answer should also be fully phenomenologically legitimate: a non-trivial, legitimate answer.

A large number of empirical and natural scientific theories of consciousness exist (cf. e.g. Seth, 2007, 2018; Bayne & Seth, 2022; Signorelli et al., 2021). No article could possibly have enough space to present just the moderately influential ones. Here, we can only mention the most prominent theories and approaches, those which are directly relevant to the issues addressed in the present paper.

Perhaps the three most well-known and influential approaches in consciousness studies are the neural correlates of consciousness (NCC) (Crick & Koch, 1990), integrated information theory (IIT) (Tononi, 2004), and global workspace theory (GWT) (Baars, 1988). NCC seeks the minimal necessary and sufficient neural set for the constitution of a concrete conscious percept. IIT connects consciousness to the causal structure of a physical system that specifies a maximum amount of irreducible integrated information (cf. also Bayne & Seth, 2022, p. 441). Consciousness, according to GWT, means ‘global availability’ for a number of different general cognitive capabilities, such as attention, memory, evaluation, and communication. An unconscious process becomes conscious when it enters a special cognitive terrain called the ‘global workspace’. The neurobiologically elaborated version of GWT, the ‘global neuronal workspace’ (e.g. Dehaene, 2014), connects this global workspace to certain cortical regions.

From a phenomenological point of view, we should state the following regarding these approaches. NCC is a specific research method to identify the minimal neural substrates for a particular state, process, or manifestation of conscious content rather than a holistic, overarching theory of consciousness. IIT, from our viewpoint, is all too ‘generous’. It attributes a certain grade of consciousness to every piece of integrated information; thus, it is open to panpsychism (Koch & Tononi, 2015), a phenomenologically unjustifiable view that we hope to avoid. GWT, on the one hand, in its neurobiological interpretation, is all-too cortex-bound, which is not confirmed by the previously mentioned principle of maximal extensibility. On the other hand, it is also all-too general and formal, meaning it does not imply a particularly concrete and coherent set of physical structures as the basis for such cognitive and conscious faculties necessary for a concrete conscious existence, according to the considerations of Subsections 2.2 and 2.4.

The last several years have witnessed several further ambitious attempts to offer a systematic phylogenetic and neurobiological explanation for the emergence of consciousness; we highlight two here. Feinberg and Mallatt (2016) believe that a specific neural architecture, a complex set of nested and non-nested neural hierarchies, can model internal and external environments such that phenomenal consciousness of a certain grade of complexity accompanies it as an intrinsic feature of this peculiar form of neuronal modelling. Ginsburg and Jablonka (2019) asserted that a specific cognitive capability and underlying neural structure represent a highly reliable indicator of phenomenally conscious mental states, namely, the faculty of ‘unlimited or open-ended associative learning’, which – for them – referred to the dynamic capability of behavioural adaptation to a perpetually changing environment.Footnote 24

Feinberg and Mallatt assume that the fundamental conscious capabilities (exteroceptive, interoceptive, affective-evaluative) evolved separately, independent from each other. Therefore, they claim that from an evolutionary, phylogenetic perspective, distal exteroceptive senses (such as vision) became conscious first, with the emergence of the first Arthropoda (more specifically, insects). This view that the fundamental conscious capabilities can be essentially separated from each other, however, violates the principle of concreteness of the minimal mind (the minimal context thesis). As concerns the model of Ginsburg and Jablonka, it is rather general regarding the specific neural architecture of concrete consciousness and, at least for me, the direct link between phenomenal consciousness and the capability of ‘unlimited or open-ended associative learning’ has not been made exceedingly clear and explicit.

Despite Feinberg and Mallatt’s model not harmonizing with a phenomenological conception concerning the concreteness of the minimal mind and Ginsburg and Jablonka’s approach not being very specific regarding the concrete neuronal bases of consciousness, both models offer the great advantage of claiming that structural and neurological foundations – at least from a phylogenetic perspective – lie much deeper than the cortex; thus, they enable us to legitimately extend the capability of consciousness beyond the level of mammals, and according to these authors, as far as insects. This satisfies the abovementioned principle of maximal legitimate extensibility of consciousness. There are other subcortical models of consciousness, however, which harmonize more fully with an overall phenomenological account of the minimal mind.

From the considerable number of different subcortical models, we highlight here Bjorn Merker’s approach (2005, 2007), which updated and further developed Penfield and Jasper’s theory (1954) as a conception which perhaps best suits a phenomenological account of the minimal mind such as that we treated in Section 2. Merker’s theory, on the one hand, conceives of the fundamental form of consciousness (core, minimal, or primary consciousness) as a concrete way of functioning and an interrelated system of specific conscious modes; it connects consciousness to such a functional architecture (a group of systematically cohering and cooperating subcortical structures) which – according to current information regarding the neurological bases of consciousness – is capable of opening the way to the maximal possible extension of the capability of consciousness.

Merker believes that consciousness emerged during evolution as an intrinsically necessary consequence of certain neural logistics that helped animals to cope with specific environmental challenges. These neural logistics created in animals a behavioural ‘core control system’ that granted them a dynamic decision-making system (2005). Such a ‘core control system’ implies and includes several factors which – according to Merker – were crucial for an elementary form of consciousness. These were an integrated, multisensory model of self and world, a complex representation of the subject’s moving body in a constantly changing environment, and memory.Footnote 25 This dynamic, complex modelling of internal and external environments, along with memory, were inherently connected to the other essential aspect of this ‘core control system’, called the ‘selection triangle’ (2007). This refers to the abovementioned dynamic decision-making system, whose fundamental components are action selection, target selection, and motivation.

In Merker’s interpretation, these functions together inevitably realize consciousness too, and all their neurological foundations can be found in the mesodiencephalic regions of brain. More specifically, he claims that the selection triangle can be specified as follows: the substantia nigra pars reticulata as the source of the collicular action selection signal, the hypothalamus and PAG as the source of the motivational, and the colliculus itself as the source of target-selection information. However, using these sources to constitute consciousness requires their integration within a joint and unitary ego-centric coordinate system supplied by the ego-centric spatio-motor mapping framework of the colliculus itself (2007, p. 72).

For Merker, this system is structurally isomorphic to all vertebrates and could possibly be extended even to embrace lower invertebrates, such as insects. But how might such a model be empirically verified? On the one hand, Merker refers to experiments on animals whose cortex had been surgically removed, noting that they nevertheless exhibited clear signs of consciousness (2007; cf. also Panksepp et al., 1994; Panksepp, 2005; Barron & Klein, 2016). On the other hand, he cites and analyses cases of children with hydranencephaly, which is a tragic congenital malformation whereby children are born without the majority of or the entire cortex. These children, Merker tries to show, still behave and react to environmental stimuli in an explicitly and evidently conscious way. However, these are third-person perspective-related cases and experiments.

In my opinion, Merker’s conception concerning the origins of consciousness dovetails best with the fundamental insights of the phenomenological approach outlined earlier. There are several crucial points that make Merker’s theory possibly the best current empirical third-person correlate for the phenomenological approach that we delineated above (in Section 2 and the first half of the present subsection). First and foremost, Merker characterizes consciousness as an intrinsic feature of the ‘core control system’, in which motivation and complex decision-making are crucial factors. This system enables a living being to adapt dynamically to a threatening environment which changes continually and rapidly. In Merker’s view, consciousness is an essentially concrete and coherent phenomenon related to the life-process of an organism which must make decisions quickly and effectively in order to survive. This interpretation seems to entail all the fundamental components which we earlier attributed to a phenomenological conception of minimal mind (Subsection 2.5). Specifically, it is the concrete and holistically organized consciousness of an embodied being with an intricate motivational basis,Footnote 26 an ego-centric perspective on the world, and fundamental mental capabilities that include learning, memory, temporally extended perception, and anticipation, which contribute to the constitution of its concreteness.

Secondly, because of its special emphasis on subcortical structures (especially parts of the mesencephalon and diencephalon), this model enables a wide extension of the capability of consciousness in the natural world while preserving the fundamental structural continuity between human and non-human conscious beings. A cortex-bound theory would drastically limit the spread of consciousness in the living world. If we accept and take seriously the indirect pieces of evidence which indicate the presence of conscious activity in living beings without a cerebral cortex, it seems evident that the cortex is not responsible for the phenomenon of consciousness as such but only for its higher and more sophisticated forms.

There remains, however, the serious question of how to verify a subcortical theory of consciousness phenomenologically.

3.2 A proposed way to prove a subcortical theory of consciousness from the first-person perspective: general anaesthesia

In phenomenology, there is a key factor of verification for an intersubjective, scientific community: the communication of one’s first-person perspective experiences. This obviously fails in the cases of decorticated animals and children with hydranencephaly, who cannot communicate.

In my opinion, experiments based upon emergence from general anaesthesia might help to identify the neurological bases of consciousness. The underlying idea is this: under general anaesthesia, the neural activity of the brain is minimized, and the particular way in which the brain ‘reboots’ could be by orientating the neurophysiological structures necessary for consciousness. Scientists have been systematically using such experiments in researching consciousness for at least twenty years; the oldest related experiments go back to the beginning of the 1980s (Uhl et al., 1980).

In this context, it should be noted that general anaesthesia does not shut down the brain globally. This could be achieved by a drug-induced coma, although this is not permitted for experimental purposes as it is too risky. For general anaesthesia, doctors use various anaesthetic drugs and their ‘cocktails’, each of which affect brain regions differently (cf. Bonhomme et al., 2019). General anaesthesia, however, could still minimize neural activity in the brain and suppress consciousness so as to provide highly valuable and orientating information regarding the neural bases of consciousness. In this section, I propose a specifically modified version of these experiments which – to my knowledge – has not yet been conducted in this form.

During emergence from general anaesthesia, the brain reaches its pre-anaesthetic, normal level of activity in a very complicated way. Bottom-up and top-down processes in parallel characterize the process of restoration. On the one hand, there is linear progress in the activation of bodily structures from the simpler to the more complex: a slow return of brainstem reflexes, then uncoordinated somatic movements, followed by the return of higher functions (Långsjö et al., 2012: 4940). On the other hand, higher functions simultaneously return along with the lower ones: there is increasing activation of the cortex from the very beginning, in parallel with the restoration of simpler neurophysiological functions (Mashour et al., 2021). These processes continually communicate with and support each other. In fact, as a recent study shows, the first neural structure to reach the ‘baseline’, the pre-anaesthetic level of activity, is the executive and problem-solving part of the prefrontal cortex (Mashour et al., 2021).

Because cortical processes are present from the start during awakening from general anaesthesia, many authors presume that these experiments rather support the cortical models of consciousness, and global neuronal workspace theory in particular (Mashour et al., 2021). However, the overall results of these experiments are, at the moment, far from unambiguous. They do not currently provide conclusive support for any model of consciousness. Perhaps the most important outcome so far is that the brain restores itself after general anaesthesia in a highly complicated way through parallel series of lower and higher processes which mutually support and enhance one another. Nevertheless, I believe that such an experiment could contribute to the verification or falsification of a subcortical theory of consciousness from the first-person perspective.

There are two major problems with testing the subcortical theory of consciousness with anaesthetic experiments. First, when patients or test subjects are awake and capable of verbally reporting on their mental states, the entire brain, including the full cortex, is operational. In other words, it is already too late. This is why many scientists have viewed these real-world experiments as supporting a cortical theory of mind. Second, emergence from general anaesthesia is usually followed by a few minutes of temporary amnesia. Thus, patients or test subjects cannot accurately report their experiences immediately upon waking from anaesthesia, which would be crucial for a phenomenological analysis of such experiences.

I believe that an experiment prepared and conducted carefully enough could address these difficulties. As a general principle, I suggest that an experiment that aims to test a subcortical theory of consciousness should focus on the behaviour of the mesodiencephalic parts of the brain during emergence from anaesthesia, utilizing the appropriate neuroimaging technologies (such as fMRI and PET). More specifically, regarding the first point above, I propose the following suggestions.

On the one hand, I assume this experiment would require a special anaesthetic ‘cocktail’. First, we need a drug that minimizes cortical activity as much as possible and disrupts communication between the cortex and thalamus. Propofol would serve this purpose (cf. Bonhomme et al., 2019). Second, another chemical component is needed which enhances the activity of the specific subcortical areas whose role in the emergence of consciousness we would like to test. Several pharmacological substances have an effect on such deeper regions of the brain, including Levodopa or amphetamines.Footnote 27 During emergence, the task of the researchers would be to slow down the reactivation of the cortex as much as possible while simultaneously speeding up the restoration of subcortical areas as much as they can.

On the other hand, testing for the presumable presence of consciousness should take place, again, as early as possible: immediately upon awakening from anaesthesia. When the test subject is able to speak, it is already too late because the ability to report verbally presupposes a relatively high level of cortical activity.

To this (subcortically focused) type of general anaesthesia experiment, we can connect directly and indirectly first-person-related clinical testing techniques. There are at least two sorts of indirectly first-person-related methods. First, according to recent studies, checking brain stem reflexes could be used as a considerably reliable indicator of the early emergence of minimally conscious states; this procedure could also be applied to anaesthetic experiments (Bao et al., 2019). Second, there are certain learnt, voluntary behavioural patterns whose appearance during quasi-sedated, not-yet-fully-aware states (such as the early stage of emergence from general anaesthesia before the full activation of the cortex) could be used as indirect evidence for the presence of consciousness (cf. Birch, 2022, pp. 140–147).Footnote 28

Regarding directly first-person-related techniques, the task would be to retrieve hypothesized memories before the full activation of the cortex, when only subcortical structures have reached moderate or normal levels of activity. In my opinion, retrieval cues and mental reinstatement of context, in particular, where reproduction of the original situation is used to access forgotten or unconscious memories, could be helpful in this respect (cf. Goldstein, 2011; Griggs, 2012; Wheeler & Gabbert, 2017). Based upon these types of retrieval methods, the patient should be stimulated by certain characteristic, composite visual and/or auditive patterns before the full recurrence of cortical activity. A couple of minutes later, in a fully awakened state, if the patient is capable of completing the pattern given to her in part (or if it at least seems familiar to her), that would be convincing evidence for the subcortical theory of consciousness.Footnote 29

These considerations suggest that while it may be very challenging, subcortical theories of consciousness can be made accessible for a phenomenological description. In this way, such experimental procedures could be also investigated using empirically related phenomenological methods, such as neurophenomenology (Varela, 1996) and micro-phenomenology (Petitmengin et al., 2018).Footnote 30

The last crucial question of our study is this: if we assume that a subcortical theory of consciousness could be verified from a first-person related phenomenological perspective, then how far could the boundaries of legitimate attribution of consciousness be extended beyond the human world into nature?

3.3 Conclusion: the presumable borders of consciousness in the natural world

We prefer the subcortical theories of consciousness, and Bjorn Merker’s conception in particular, for two reasons. First, they seem best suited to a phenomenological approach to consciousness. Second, they grant a legitimate and, from an empirical regard, properly grounded maximal extension of the capability of consciousness in the natural world. If the model provided by Merker is accurate, then all vertebrates, and maybe even some lower invertebrates, such as insects, are conscious.

If a subcortical model of consciousness (versus a cortical one) could be verified, it would mean that the cortex is not responsible for the very being of consciousness in general but only for its higher and more sophisticated forms.

To be sure, even if a thalamocortical (e.g. Llinás et al., 1998) or cortical (e.g. global neuronal workspace theory) model of consciousness were proven accurate, unlike a subcortical model, it would still not mean that only mammals and birds could be conscious beings. As far as we know, it is not the specific cerebral regions themselves that are crucial in the generation or activation of consciousness but a certain functional architecture, a particular set of neural pathways necessary for being conscious.

Regarding GWT, Bernard Baars emphasizes that it is essentially a cognitive model of consciousness and, in principle, has nothing to do with the cortex. (‘The 1988 version of GWT made no assertions about the role of cortex in consciousness. These claims are mistaken, and indeed, self-contradictory’; Baars et al., 2021). Accordingly, Shanahan (2016), for example, claims that GWT could be reconciled with a considerably modified Merker model offered by Andrew Barron and Colin Klein (2016) and, thus, could be extended even to insects.Footnote 31

I would suggest, however, that we should prefer a subcortical model of consciousness which is smaller in size and in the number of involved functional units from the outset. This would be more economical than a cortical model. Although, as we mentioned, the emergence of consciousness most probably depends on a specific functional architecture, it also seems very likely that the functional units (in this case, neurons) and their connections in this architecture cannot go below a certain number if it is expected to sustain a concrete form of consciousness permanently and coherently. Thus, living beings with fewer than a certain number of neurons and their connections cannot be conscious in the strict sense. I believe this because panpsychism, and even biopsychism (the assumption that every living being is conscious), are phenomenologically unjustifiable from the first-person perspective of an adult human person.

I deem that from an empirical standpoint, Bjorn Merker’s approach is currently one of the best conceptions regarding the emergence of consciousness that also contains every fundamental element and structure – along with their proper relations – prescribed by a detailed phenomenological description of the minimal mind. In Merker’s model (unlike IIT), it is not indifferent which type of information is integrated and how. Furthermore, within this framework, the integration and procession of the proper pieces of information is enough for consciousness; the ‘broadcast effect’, a requisite in GWT, is not required. Thus, Merker’s conception is more economical than GWT. In my opinion, it is a simple, non-trivial, and elegant model of consciousness, which is also strongly supported by a first-person phenomenological approach.

Finally, in concluding our study, we should make one last important remark. Our phenomenological stance imposes certain very strong constraints regarding the testability of a theory of consciousness – namely, there must be certain empirical conditions under which it can be tested and verified. Otherwise, from the phenomenological perspective, such a theory would remain completely hypothetical and speculative. Accordingly, if an insect, such as a honeybee, is conscious, which is a possible implication of Merker’s theory and an explicit claim of Barron and Klein, then such a theory must be capable of verification from the first-person perspective of a normal adult human person. In other words, if such an extension of consciousness (e.g. to insects) is supposed to be true, then there must be certain empirical circumstances when, in the case of a healthy adult human, only those neural circuits are in function which are held responsible for consciousness in insects, and the human in question can later somehow confirm that during this extremely low level of neural functioning, she had conscious experiences.