Is a naturalized phenomenology a desideratum or a category mistake? In the following, I will argue that the answer to this question very much depends on what one takes the question to be, and that we need to distinguish at number of very different readings of what both phenomenology and naturalization amounts to.

Let me start by taking a step back in history. In a lecture entitled Phänomenologie und Psychologie from 1917, Edmund Husserl raised the following question: Why introduce a new science entitled phenomenology when there is already a well-established explanatory science dealing with the psychic life of humans and animals, namely psychology. More specifically, psychology is a science of naturalized consciousness. And could it not be argued that a mere description of experience – which is, supposedly, all that phenomenology can offer – does not constitute a viable scientific alternative to psychology, but merely a – perhaps indispensable – descriptive preliminary to a truly scientific study of the mind.Footnote ¹ As Husserl remarked, this line of thinking – which he was strongly opposed to – had appeared so convincing that the term ‘phenomenological’ was being used in all kinds of philosophical and psychological writings to label a direct description of consciousness based on introspection.Footnote ² The parallel to the contemporary discourse is quite striking. Currently, the term ‘phenomenology’ is also being used by many cognitive scientists and analytic philosophers of mind to designate either the what-it-is-likeness of experience or the first-person description of this experiential character. Given such a reading of what phenomenology amounts to, to speak of and envisage a naturalized phenomenology is typically understood as addressing Chalmers' hard problem or Levine's explanatory gap.Footnote ³ It is a question of acknowledging that a truly scientific theory of consciousness cannot allow itself to ignore the phenomenological dimension. It must address the topic of subjectivity for otherwise it will be disregarding a crucial aspect of the explanandum. But in addition to acknowledging that phenomenology is part of the explanandum, the call for its naturalisation is also an attempt to avoid any residue of mysterianism (cf. Flanagan's criticism of Nagel and McGinn)Footnote ⁴ since the aim is precisely to give a natural explanation of consciousness. It is to show how the experiences we are all so familiar with from the first-person perspective are ultimately amenable to a natural scientific investigation and explanation.

This is, as I said, one version of what a naturalized phenomenology amounts to. It is, however, not the type I will be focusing on. Rather, when I in the following discuss phenomenology, I will be referring to the tradition of philosophical phenomenology founded by Husserl and continued and further developed by thinkers such as Heidegger, Sartre and Merleau-Ponty.

But isn't this a distinction without a difference? After all, in Consciousness Explained, Dennett criticized philosophical phenomenology for employing an unreliable introspectionist methodology and argued that it had failed to find a single, settled method that everyone could agree upon.Footnote ⁵ A comparable view can be found in Metzinger, who recently concluded that ‘phenomenology is impossible’.Footnote ⁶ What kind of argument do these theorists provide? The basic argument seems to concern the epistemological difficulties connected to any first-person approach to data generation. If inconsistencies in two individual data sets should appear, there is no way to settle the conflict. More specifically, Metzinger takes data to be such things that are extracted from the physical world by technical measuring devices. This data extraction involves a well-defined intersubjective procedure, it takes place within a scientific community, it is open to criticism, and it constantly seeks independent means of verification. The problem with phenomenology, according to Metzinger, is that first-person access to the phenomenal content of one's own mental state does not fulfil these defining criteria for the concept of data. In fact, on his view, the very notion of first-personal data is a contradiction in terms.Footnote ⁷

But is it really true that philosophical phenomenology is based on introspection? Consider Husserl's Logische Untersuchungen, a recognized milestone in 20th century philosophy and indisputably a work in phenomenological philosophy. What kind of analyses does one find in this book? One finds Husserl's famous attack on and rejection of psychologism; a defence of the irreducibility of logic and the ideality of meaning; an analysis of pictorial representations; a theory of the part-whole relation; a sophisticated account of intentionality; and an epistemological clarification of the relation between concepts and intuitions, to mention just a few of the many topics treated in the book. Does Husserl use an introspective method, and is this a work in introspective psychology? Anyone who reads Logische Untersuchungen should answer ‘no’, since what one finds there are clearly philosophical arguments and analyses. Rather than concluding that this work is not phenomenology, one should rather reconsider the hasty identification of phenomenology and introspective psychology.

Phenomenological disputes as well as disputes among phenomenologists are philosophical disputes, not disputes about introspection. Although it would be an exaggeration to claim that Husserl's analyses in Logische Untersuchungen found universal approval among the subsequent generations of phenomenologists, I don't know of any instance where Husserl's position was rejected on the basis of an appeal to ‘better’ introspective evidence. On the contrary, Husserl's analyses gave rise to an intense discussion among phenomenological philosophers, and many of the analyses were subsequently improved and refined by thinkers like Sartre, Heidegger, Lévinas, and Derrida.Footnote ⁸ It is also noteworthy that all the major figures in the phenomenological tradition have openly and unequivocally denied that they are engaged in some kind of introspective psychology and that the method they employ is a method of introspection.Footnote ⁹ Classical phenomenology is not just another name for a kind of psychological self-observation; rather it must be appreciated as a special form of transcendental philosophy that seeks to reflect on the conditions of possibility of experience and cognition. Phenomenology is a philosophical enterprise; it is not an empirical discipline. This doesn't rule out, of course, that its analyses might have ramifications for and be of pertinence to an empirical study of consciousness, but this is not its primary aim. This is also why, Husserl himself categorically rejects the attempt to equate the notion of phenomenological intuition with a type of inner experience or introspection,Footnote ¹⁰ and even argues that the very suggestion that phenomenology is attempting to restitute the method of introspection (innere Beobachtung) is preposterous and perverse.Footnote ¹¹ This clearly contrasts with Metzinger's claim that the phenomenological method cannot provide a method for generating any growth of knowledge since there is no way one can reach intersubjective consensus on claims like ‘this is the purest blue anyone can perceive’ versus ‘no it isn't, it has a slight green hue’.Footnote ¹² These kinds of claims are simply not the kind that are to be found in works by phenomenological philosophers and to suggest so is to reveal one's lack of familiarity with the tradition in question.

If we for now focus on philosophical phenomenology, it is quite controversial, to put it mildly, whether it can and ought to be naturalized – whatever that is then supposed to mean. The question has been discussed for quite a while, but there is no doubt that Francisco Varela's recent work on neurophenomenology has been decisive in rekindling interest in the issue.

The very term ‘neurophenomenology’ was first coined by Laughlin, McManus and d'Aquili in 1990,Footnote ¹³ but was then subsequently appropriated and redefined by Varela, who envisaged it as a novel approach in cognitive science.Footnote ¹⁴ The term has since then been used in both a narrow and a broader sense. In the more narrow sense, neurophenomenology refers to Varela's specific proposal, which, as I will explain in a moment, emphasized the embodied character of the human mind and sought to combine neuroscience with phenomenology in the study of experience and consciousness. This proposal was subsequently taken up and further developed by for instance Lutz and Thompson.Footnote ¹⁵ In the broader use of the term, neurophenomenology refers to various attempts to naturalize phenomenology, attempts that are all guided by the idea that (philosophical) phenomenology and empirical science are mutually constraining and enlightening projects.Footnote ¹⁶

Merleau-Ponty's work (along with that of, for instance, Gurwitsch and Straus) has been an obvious source of inspiration for many of the participants in the debate. Thus, Merleau-Ponty has been heralded as someone who already early on ‘argued for the mutual illumination among a phenomenology of direct lived experience, psychology and neurophysiology’.Footnote ¹⁷ The role of Husserl has been more controversial. Whereas Husserl was early on dismissed as a Cartesian, a representationalist and methodological solipsist who ignored the embodied and consensual aspect of experience,Footnote ¹⁸ the subsequent debate has been characterized by a remarkable change of appraisal. The change is so noticeable that Thompson has recently found reason to offer an explanation himself.Footnote ¹⁹ As he explains, when he co-authored The Embodied Mind not only did he have limited knowledge of Husserl's own writings and of the relevant secondary literature; his interpretation was also influenced by Heidegger's uncharitable reading of Husserl, as well as by the quite influential and dismissive criticism that Dreyfus gave voice to in the early volume Husserl, Intentionality and Cognitive Science. And as Thompson concludes, although Dreyfus should be credited for having brought Husserl into the purview of cognitive science, it is urgent ‘to go beyond his interpretation and to reevaluate Husserl's relationship to cognitive science on the basis of a thorough assessment of his life's work’.Footnote ²⁰

According to Varela's more specific proposal, neurophenomenology is an approach that rejects representationalist and computationalist accounts of consciousness and cognition, and which considers the data from phenomenologically disciplined analyses of lived experience and the experimentally based accounts found in cognitive neuroscience to have equal status and to be linked by mutual constraints. If cognitive science is to accomplish its goal, namely to provide a truly scientific theory of consciousness, it must not ignore the phenomenological dimension. To put it differently, if our aim is to have a comprehensive understanding of the mind, focusing narrowly on the nature of the sub-personal events that underlie experience without considering the qualities and structures of the experience itself will just not take us very far. More specifically, Varela argued that the subjective dimension is intrinsically open to intersubjective validation, if only we avail ourselves of a method and procedure for doing so. He thought classical philosophical phenomenology had provided such a method.Footnote ²¹

It is consequently important to realize that Varela's neurophenomenological proposal amounts to far more than simply insisting that a satisfactory account of consciousness has to take the first-personal or subjective dimension of consciousness seriously. When Varela refers to phenomenology, he is precisely not using the term in its nontechnical sense (like Flanagan, Block, Chalmers and others), i.e., as some introspective account of ‘what it is like’ to undergo a certain experience. Rather he is referring to a specific philosophical tradition.

More specifically, Varela sought to incorporate phenomenological forms of investigation into the experimental protocols of neuroscientific research on consciousness. The experimental subjects were trained to gain greater intimacy with their own experiences. They were taught to bring into focus dimensions and aspects of consciousness that were normally not attended to. The subjects were subsequently asked to provide careful description of these experiences using an open-question format, and thus without the imposition of pre-determined theoretical categories. The ensuing descriptive categories were subsequently validated intersubjectively and then used to constrain and facilitate the analysis and interpretation of the correlated neuro-physiological processes.Footnote ²²

Varela's initial publications in the area generated an intense debate about the relation between phenomenology and cognitive science, and more generally about whether phenomenology could and ought to be naturalized. Yet another milestone in this debate was the landmark volume Naturalizing Phenomenology from 1999, where Varela and his three co-editors again argued that it was crucial for the future development of cognitive science that cognitive scientists learned to use some of the methodological tools that were developed by Husserl and Merleau-Ponty.Footnote ²³

Despite the very explicit reference to the Husserlian tradition, the four editors of the volume did however see their proposal as a contribution to a solution, or perhaps dissolution, of the hard problem. They argued that their ultimate goal was to provide a natural explanation of consciousness, i.e. to avoid any residue of dualism, and that this would entail that phenomenology became integrated into an explanatory framework where every acceptable property was continuous with the properties admitted by natural science.Footnote ²⁴ On such a reading, a naturalization of phenomenology would be one that eventually made phenomenology part of, or at least an extension of, natural science.

If this is what a naturalized phenomenology amounts to, is it then a desideratum or a category mistake? From the point of view of orthodoxy, there is hardly any question about the answer. Let us not forget that Husserl was a staunch anti-naturalist. In the long essay Philosophie als strenge Wissenschaft from 1910–11, Husserl described naturalism as a fundamentally flawed philosophyFootnote ²⁵ and argued that it had typically had two different aims: the naturalization of ideality and normativity, and the naturalization of consciousness.Footnote ²⁶ In his view, however, both attempts were misguided and both failed. The naturalistic reduction of ideality led to scepticism.Footnote ²⁷ This, in fact, was one of Husserl's main arguments in his famous fight against psychologism in Logische Untersuchungen. As for Husserl's criticism of the attempt to naturalize consciousness, he explicitly contrasted his own phenomenology of consciousness with a natural scientific account of consciousness.Footnote ²⁸ Both disciplines investigate consciousness, but according to Husserl they do so in utterly different manners. And to suggest that the phenomenological account could be absorbed, or reduced, or replaced by a naturalistic account was for Husserl sheer nonsense. This is not to say that Husserl didn't respect natural science, but as he famously put it in Ideen I, ‘When it is actually natural science that speaks, we listen gladly and as disciples. But it is not always natural science that speaks when natural scientists are speaking; and it assuredly is not when they are talking about ‘philosophy of Nature’ and ‘epistemology as a natural science’’.Footnote ²⁹

Why did Husserl oppose the attempt to implement a thorough naturalistic account of consciousness? Because naturalism in his view is incapable of doing full justice to consciousness. Not only has it – in the shape of experimental psychology – tended to lose sight of (subjective) consciousness,Footnote ³⁰ but even more importantly, naturalism treats consciousness as an object in the world, on a par with – though possibly more complex than – volcanoes, waterfalls, ice crystals, gold nuggets, rhododendrons or black holes. But on Husserl's view this is unacceptable since consciousness rather than merely being an object in the world, is also a subject for the world, i.e., a necessary condition of possibility for any entity to appear as an object in the way it does and with the meaning it has. To put it differently, according to Husserl, the decisive limitation of naturalism is that it fails to recognize the transcendental dimension of consciousness.

Let me dwell a bit more on this specific issue, since it is frequently misunderstood. When Husserl denies that consciousness is an objective occurrence that exists side by side with the object of which it is conscious, he is not denying the possibility of a reductive account of qualia and urging us to adopt some kind of non-reductive or even dualist account. Ultimately, Husserl is not at all interested in the question of what kind of stuff consciousness is made of, and to read him in this way is not only to misunderstand his philosophical project, but also that of other phenomenologists. Consider for instance Merleau-Ponty who declares that phenomenology is distinguished in all its characteristics from introspective psychology and that the difference in question is a difference in principle. Whereas the introspective psychologist considers consciousness as a mere sector of being, and tries to investigate this sector in the same way the physicist tries to investigate the physical world, the phenomenologist realizes that consciousness ultimately calls for a transcendental clarification that goes beyond common sense postulates and brings us face to face with the problem concerning the constitution of the world.Footnote ³¹

The simplest way to understand such claims is by acknowledging that phenomenology – despite all kinds of other differences – is firmly situated within a certain Kantian or post-Kantian framework. One way to interpret Kant's revolutionary Copernican turn is by seeing it as amounting to the conviction that our cognitive apprehension of reality is more than a mere mirroring of a pre-existing world. Thus, with Kant the pre-critical search for the most fundamental building blocks of reality was transformed into a transcendental philosophical reflection on what conditions something must satisfy in order to count as ‘real’. With various modifications this idea was picked up by Husserl and subsequent phenomenologists. Phenomenology shares the conviction that the critical stance proper to philosophy necessitates a move away from a straightforward metaphysical or empirical investigation of objects to an investigation of the very framework of meaning and intelligibility that makes any such straightforward investigation possible in the first place. Indeed, rather than taking the objective world as the point of departure, phenomenology precisely asks how something like objectivity is possible in the first place. How is objectivity constituted?

Husserl is ultimately committed to the view that reality depends transcendentally upon consciousness (though, on my own reading, he eventually veered towards a view that to a larger extent emphasized the importance of facticity and passivity and the interdependence of subjectivity, intersubjectivity and world – but that is another story).Footnote ³² This view has various metaphysical implications – it has implications for our fundamental understanding of what counts as real and it entails a rejection of metaphysical realism – but it doesn't entail that consciousness is the metaphysical origin or source of reality. Husserl might indeed consider consciousness a necessary condition for reality. Thus, for Husserl nothing would exist in the absence of consciousness. But there is a long way from such a claim to the far more radical claim that consciousness is a sufficient condition.Footnote ³³

Given such a commitment, it is again not surprising that phenomenology's response to naturalism has been rather unequivocal. Contrary to some proposals, it is not naturalism's classical endorsement of some form of physicalism that constitutes the main obstacle to a reconciliation. It is not as if matters would improve if naturalism opted for some version of emergentism or property dualism. The real problem has to do with naturalism's commitment to metaphysical realism and objectivism. For Husserl, naturalism takes its subject matter, nature, for granted. Reality is assumed to be out there, waiting to be discovered and investigated. And the aim is then to acquire a strict and objectively valid knowledge about this given realm. But for Husserl this attitude must be contrasted with the properly philosophical attitude, which critically questions the very foundation of experience and scientific thought.Footnote ³⁴ Husserl has frequently been accused of being a foundationalist. To some extent this is correct. Husserl is a transcendental philosopher, and he would insist that transcendental phenomenology investigates the condition of the possibility for experience, meaning, and manifestation, and thereby also the very framework of intelligibility that is presupposed by any scientific inquiry. On his view, philosophy is a discipline which doesn't simply contribute to or extend the scope of our scientific knowledge, but which instead investigates the basis of this knowledge and asks how it is possible. It is against this background that the attempt to naturalize phenomenology seems fundamentally misguided. As Husserl explained to the Neo-Kantian Rickert in a letter from 1915, he considered the fight against naturalism – a fight he had devoted his life to – indispensable for the progress of philosophy.Footnote ³⁵ Indeed, for Husserl a phenomenologist who embraced naturalism would in effect have ceased being a philosopher.

As I also pointed out in an article published in 2004, if one understands naturalized phenomenology in line with the programmatic statements found in the introduction to the volume Naturalizing Phenomenology, the proposal to naturalize phenomenology does indeed seem fundamentally misguided.Footnote ³⁶ Were one to implement this strategy, one would by the same token abandon much of what makes phenomenology philosophically interesting. Phenomenology is basically, to repeat, a transcendental philosophical endeavour, and although one might ease the way for its naturalization by abandoning the transcendental dimension, one would not retain that which makes phenomenology a distinct philosophical discipline, strategy, and method.

Of course, some might claim that this only adds further arguments in favour of naturalizing phenomenology, since one would thereby discard the (obsolete) transcendental philosophical aspect of phenomenological philosophy and instead preserve what might be of more lasting value, namely those concrete phenomenological analyses that remain pertinent for, e.g., social philosophy, philosophical anthropology, and philosophy of mind. This is not a view I share, but for now my aim is not to try to defend the merits of transcendental phenomenology (I have tried to do so elsewhere), but simply to point to the tension between this transcendental aspiration and the project of naturalization.

It was also this tension that Leonard Lawlor had in mind when he recently wrote that all forms of naturalism are incapable of solving the transcendental problem that was of concern to Husserl and that the project of naturalization in general and especially the project of naturalizing phenomenology only makes the crisis addressed by Husserl in his late work Die Krisis der europäischen Wissenschaften und die transzendentale Phänomenologie even worse.Footnote ³⁷

But, and there is a ‘but’, there are other ways of understanding what a naturalization of philosophical phenomenology amounts to than the way just outlined.

Let me in the following sketch two alternative takes on what a naturalized phenomenology might amount to. I want to suggest that our appraisal of the desirability of a naturalized phenomenology should be more positive, if we opt for one or both the following proposals.

A very different way of approaching the issue – a way that has both classical roots, but which has also received quite a dramatic revival in recent years – is to hold that a naturalization of phenomenology simply entails letting phenomenology engage in a fruitful exchange and collaboration with empirical science. The phenomenological credo ‘To the things themselves’ calls for us to let our experience guide our theories. We should pay attention to the way in which we experience reality. Empirical scientists might not pay much attention to deep philosophical questions, but as empirical researchers they do in fact pay quite a lot of attention to concrete phenomena and might consequently be less apt to underestimate the richness, complexity, and variety of the phenomena than the standard arm-chair philosopher. To put it differently, phenomenology has traditionally studied various aspects of consciousness (including perception, imagination, body-awareness, attention, intentionality, social cognition, self-experience and recollection) that are also open to empirical investigation, and, as it is claimed, it would be wrong for phenomenology to simply ignore empirical findings pertaining to these very aspects. On the contrary, it should be informed by the best available scientific knowledge. Empirical science can present phenomenology with concrete findings that it cannot simply ignore, but must be able to accommodate; evidence that might force it to refine or revise its own analyses. At the same time, phenomenology might not only contribute with its own careful descriptions of the explanandum, but might also question and elucidate basic theoretical assumptions made by empirical science, just as it might aid in the development of new experimental paradigms. Thus, as a recent proposal entitled front-loaded phenomenology Footnote ³⁸ has it, rather than focusing on the training of experimental subjects, insights developed in phenomenological analyses might also inform the way experiments are set up. To take a concrete example, consider the issue of self-consciousness. Within developmental psychology, the so-called mirror self-recognition test has occasionally been heralded as the decisive test for self-consciousness. From around eighteen months of age, children will engage in self-directed behaviour when confronted with their mirror-image, and it has been argued that self-consciousness is only present from the moment the child is capable of recognizing itself in the mirror.Footnote ³⁹ Needless to say, this line of reasoning makes use of a very specific notion of self-consciousness. Rather than simply letting phenomenological insights guide our interpretation of the results obtained through the testing of mirror self-recognition, one possibility would be to let the phenomenological account and analysis of pre-reflective self-consciousness guide our design of the experimental paradigm. It would no longer involve the testing of mirror self-recognition – which phenomenologists would typically consider evidence for the presence of a rather sophisticated form of self-consciousnessFootnote ⁴⁰– but, for instance, aim at detecting the presence of far more primitive forms of proprioceptive body-awareness. To front-load phenomenology, however, does not imply that one simply presupposes or accepts well-rehearsed phenomenological results. Rather it involves testing those results and more generally it incorporates a dialectical movement between previous insights gained in phenomenology and preliminary trials that will specify or extend these insights for purposes of the particular experiment or empirical investigation.Footnote ⁴¹

So on this proposal, the naturalization of phenomenology wouldn't merely consist in stressing the usefulness of phenomenological analyses and distinctions for, say, cognitive science. The point wouldn't merely be that phenomenology might prove indispensable if we wish to obtain a precise description of the explanandum – a sine qua non for any successful attempt to identify and localize the relevant neurobiological correlate. It wouldn't merely be a question of employing phenomenological insights in the empirical investigation of the mind. Rather, the idea would be that the influence goes both ways, i.e., it would also be a question of letting phenomenology profit from – and be challenged by – empirical findings. That is, the latter could help us improve and refine the classical phenomenological findings. This is why it is entirely appropriate to speak of a mutual enlightenment as Gallagher has done.Footnote ⁴² But to anticipate an obvious objection: How can analyses pertaining to various sub-personal processes and mechanisms possibly influence and enrich phenomenological accounts that attempt to do justice to the first-person perspective and seek to understand the experience in terms of the meaning it has for the subject?

Two things can be said in response. First, we shouldn't overlook the fact that disciplines such as psychopathology, neuropathology, developmental psychology, cognitive psychology, anthropology etc. can provide person-level descriptions that might be of phenomenological relevance. The examples are legion, but if one were to mention a few, one could single out:

1. (1) neuropsychological descriptions of various disorders of body-awareness, Consider, for example, Jonathan Cole'sFootnote ⁴³ careful analysis of Ian Waterman, who at the age of 19, due to illness, lost all sense of touch and proprioception from the neck down; compare Cole's analysis of how dramatic and disabling this impairment is, with the classical phenomenological investigation of the lived body that we find in Husserl and Merleau-Ponty.

2. (2) psychopathological descriptions of schizophrenic disturbances of self-experience and intentionality. Psychiatrists and clinical psychologists, like Minkowski, Blankenburg, Parnas and Sass, have provided careful analyses of the disturbed self- and world-experience we find in schizophrenic patients; compare such accounts to the phenomenological discussion of natural evidence and non-objectifying pre-reflective self-awareness.

3. (3) developmental descriptions of social interactions in early childhood. Compare, for example, the careful analyses provided by contemporary developmental psychologists of primitive but fundamental forms of social understanding found in infants and young children to the work on empathy, pairing and intercorporeity that we find in Scheler, Stein, Husserl and Merleau-Ponty.

Second, not only person-level accounts, but sub-personal accounts may have relevance for phenomenological analysis. For example, assume that our initial phenomenological description presents us with what appears to be a simple and unified perceptual phenomenon. When studying the neural correlates of this phenomenon, however, we discover that not only areas associated with perception, but also areas associated with episodic memory are activated. This discovery might motivate us to return to our initial phenomenological description in order to see whether the phenomenon in question is indeed as simple as we thought. Assuming that phenomenologists are not infallible and that their first attempts are not always perfect, it is possible that a more careful phenomenological analysis will reveal that the experience harbours a concealed complexity. It is important, however, to emphasize that the discovery of a significant complexity on the sub-personal level – to stick to this simple example – cannot by itself force us to refine or revise our phenomenological description. It can only serve as motivation for further inquiry. There is no straightforward isomorphism between the sub-personal and personal level, and ultimately the only way to justify a claim concerning a complexity on the phenomenological level is by cashing it out in experiential terms.

Let me emphasize that although the role assigned to phenomenology on this proposal has little to do with introspective data gathering – phenomenology is obviously also taken to have a genuine theoretical impact – its distinctive transcendental character is somewhat downplayed or even bracketed. It is therefore also relevant to point to a distinction made by Husserl himself between two rather different phenomenological approaches to consciousness. On the one hand, we have transcendental phenomenology, and on the other, we have what he calls phenomenological psychology.Footnote ⁴⁴ What is the difference between these two approaches? Both of them deal with consciousness, but they do so with quite different agendas in mind. For Husserl, the task of phenomenological psychology is to investigate intentional consciousness in a non-reductive manner, that is, in a manner that respects its peculiarity and distinctive features. Phenomenological psychology is consequently a form of descriptive, eidetic, and intentional psychology which takes the first-person perspective seriously, but which – in contrast to transcendental phenomenology, that is, the true philosophical phenomenology – remains within a pre-philosophical attitude and stops short of effectuating the reflective move needed in order to attain the stance of transcendental philosophy. The difference between the two is consequently that phenomenological psychology might be described as a local regional-ontological investigation which investigates consciousness for its own sake. In contrast, transcendental phenomenology is a much more ambitious global enterprise. It is interested in the constitutive dimension of subjectivity, that is, it is interested in an investigation of consciousness in so far as consciousness is taken to be a condition of possibility for meaning, truth, validity, and appearance.

Why is this distinction relevant? Because the first alternative we have just considered seems rather neatly to match Husserl's conception of phenomenological psychology. But what then might the second alternative amount to? The second alternative would argue that we shouldn't overlook an issue that so far has remained somewhat in the background, namely the task of really understanding what naturalism and the transcendental amount to. Let us not forget that Hume vis-à-vis the concept of nature once declared that ‘there is none more ambiguous and equivocal’.Footnote ⁴⁵

The volume Naturalizing Phenomenology had four editors. The programmatic introduction to the volume had four authors, and there are some indications in the text that they might not all have been in perfect agreement. Next to the view I presented earlier, according to which the philosophical clarification that phenomenology has traditionally offered was sought to be replaced with an explanatory account, we also find places in the introduction where the editors explicitly describe their own project as entailing a reexamination of ‘the usual concept of naturalization in order to lay bare its possible limitations and insufficiencies’.Footnote ⁴⁶ They also speak in favour of recasting the very idea of nature, and of the need for modifying our modern conception of objectivity, subjectivity, and knowledge.Footnote ⁴⁷ They explicitly reject the claim that scientific objectivity presupposes a belief in an observer-independent reality, and referring to quantum mechanics and to Heisenberg's uncertainty principle they argue that physical knowledge is about physical phenomena which are then treated in an intersubjectively valid manner.Footnote ⁴⁸ Most revealing of all, however, is perhaps a reply given by Varela to a question that I posed to him at a meeting in Paris in 2000: The volume Naturalizing phenomenology was only intended as the first part of a larger project. The second complementary volume, which unfortunately was never realized due to Varela's untimely death, was planned to carry the title Phenomenologizing Natural Science.

In his most recent book, Mind in Life, Varela's collaborator Evan Thompson has tried to take up the challenge by arguing that a naturalization of phenomenology will lead to a renewed understanding of the nature of both life and mind.Footnote ⁴⁹ Indeed, on his view, phenomenology provides a way of observing and describing natural phenomena that bring out features which would otherwise remain invisible to science; features such as selfhood, normativity, subjectivity, intentionality and temporality. Thus, one of the decisive ambitions of Mind in Life is precisely to show how phenomenology might enable us to appreciate the inner life of biological systems.Footnote ⁵⁰

A core concept at work in Thompson's account is the concept of self-organization or autopoiesis. Insofar as an organism is self-organizing, things will have significance or valence for it, and this means that it qua living being rather than being a sheer exteriority, embodies a kind of interiority. Even at the bacterial level, one can consequently distinguish an internal identity and an outside world. This interiority of life is a precursor to the interiority of consciousness (which should be viewed as a structure of engagement with the world). Life and mind share a set of basic organizational properties. The properties distinctive of mind are an enriched version of those fundamental to life. Mind is life-like and life is mind-like.Footnote ⁵¹ Thus, Thompson's general idea is that by articulating a biologically based conception of cognition that gives a natural place to the significance things have for an organism, one might connect biology to subjectivity and phenomenology, where other theories are left with an explanatory gap.

So far the point being made is simply that in discussing the relation between phenomenology and naturalism one shouldn't make the mistake of letting the concept of nature remain unexamined. One might say the same regarding the notion of the transcendental. Indeed, when assessing whether and to what extent naturalism and transcendental philosophy are compatible, it is important to remember that although Husserl's phenomenology is undoubtedly a form of transcendental philosophy, it differs rather markedly from the traditional Kantian conception of the transcendental. As I have argued elsewhere, the phenomenology of the later Husserl is characterized by its attempt to modify the static opposition between the transcendental and the empirical, between the constituting and the constituted.Footnote ⁵² It is for instance against this background that one should understand Husserl's claim that transcendental subjectivity must necessarily conceive of itself as a worldly being if it is to constitute an objective world, since objectivity can only be constituted by a subject which is both embodied and socialized.Footnote ⁵³ This was not an insight that Husserl only reached at the very end of his life. In an earlier text written around 1914–15, Husserl argues that actual being, or the being of actual reality, doesn't simply entail a relation to some formal cognizing subject, but that the constituting subject in question must necessarily be an embodied and embedded subject. Thus already in this period, Husserl is claiming that in order to constitute the world the subject must necessarily be embedded in a bodily manner in the very world that it is seeking to constitute.Footnote ⁵⁴ And as he then continues, the constitution of an objective world also requires that the subject stands in an essential relation to an open plurality of other embodied and embedded subjects.Footnote ⁵⁵ I cannot on this occasion, elaborate further on Husserl's notion of the transcendental. Suffice it to say that one of the characteristic features of phenomenological thought has been its attempt to make the co-existence of the transcendental and the empirical perspective less paradoxical. Rather than conceiving of the two as mutually incompatible, they are seen as intertwined and complementary perspectives.

According to the proposal currently being considered a naturalization of phenomenology would entail a reexamination of the usual concept of naturalization and a revision of the classical dichotomy between the empirical and the transcendental. In short, according to the current proposal, a naturalization of phenomenology might not only entail a modification (rather than abandonment) of transcendental philosophy, but also a rethinking of the concept of nature – a rethinking that might ultimately lead to a transformation of natural science itself. Regardless of how theoretically fascinating such a proposal might seem, it should, however, be obvious that the task is daunting and that there is still a long way to go.

The two alternative takes on what a naturalized phenomenology might amount to that I have just presented should not be seen as incompatible alternatives that we have to choose between. They differ in their radicality, but they might be pursued simultaneously. However, they both differ from the more traditional conception of a naturalized phenomenology that the classical phenomenologists opposed. To simply repeat what I wrote in the beginning, if we want to assess whether or not a naturalized phenomenology is a desideratum or a category mistake, we need to be clear on precisely what notion of phenomenology and what notion of naturalization we have in mind.