1.  Introduction

In contemporary discussions of disease and illness, two dominant frameworks are typically distinguished: the naturalistic theory and the normativist theory. The naturalistic approach conceives of illness primarily as a form of biological dysfunction, framing health as the proper functioning of bodily systems according to measurable physiological norms. As Brencio notes, since the Enlightenment, the study of health and disease has been excessively reliant on mechanistic and reductionist scientific paradigms. Many contemporary scholars have criticized this approach for two primary reasons: first, it neglects the holistic “human” dimension in clinical diagnosis, treating the body as a collection of isolated parts rather than as an integrated, existential whole; second, it disregards the subjective experience, consciousness, and suffering of the individual, reducing complex existential states to mere biological or statistical phenomena [1].

By contrast, the normativist approach interprets illness and disability as socially and historically constructed phenomena, emphasizing how cultural norms, institutional practices, and societal expectations define what counts as “healthy” or “normal” [2]. While this perspective addresses some limitations of the naturalistic model, it has its own shortcomings. If illness is understood solely as a social construct, it becomes relative to cultural and historical contexts, undermining cross-cultural consistency. It also complicates the establishment of stable criteria for clinical assessment and medical practice, and without integrating the first-person perspective, it risks neglecting the embodied suffering and subjective limitations intrinsic to being ill.

Both approaches thus share a key limitation: they largely overlook the lived, first-person experience of illness. As Sartre observes, being ill is distinct from being diagnosed with a disease: the former constitutes a subjective encounter with one’s own vulnerable body, while the latter objectifies the body under the clinical gaze of modern medicine [3]. Naturalistic and normativist frameworks capture only biological states or social definitions, not what it actually feels like to inhabit a body in dysfunction or pain. It is precisely here that a third approach, the phenomenological account, becomes necessary—an approach that focuses on lived experience and proceeds from the first-person perspective to understand what it means to be ill.

Building on this insight, the paper examines how a phenomenological account of health and illness can be developed from Heidegger’s philosophy, outlining both the explanatory potential and the limitations of a Heideggerian framework. It emphasizes how illness is experienced as a disruption of being-in-the-world and provides a conceptual foundation for therapeutic approaches that remain attentive to the lived body and the existentially situated patient.

Although Heidegger himself never wrote explicitly on illness, his philosophy nonetheless laid the conceptual groundwork for understanding vulnerability, corporeal limitation, and existential disruption. From 1959 to 1969, Heidegger engaged in extensive dialogue with the Swiss psychiatrist Medard Boss through the Zollikon Seminars, addressing physicians, psychiatrists, and psychologists on phenomenology and ontology. These exchanges directly influenced the therapeutic method of Dasein analysis, originally proposed by Ludwig Binswanger in the late 1920s and later developed by Boss in the postwar period, which interprets illness not merely as a physiological dysfunction, but as a limitation in a person’s capacity to relate to their own existence and to exercise care for the various dimensions of being [1].

2.  An overall account: the interdependence of health and illness

There are two contemporary approaches to conceptualizing health and illness: one grounded in Merleau-Ponty and the other in Heideggerian philosophy. This paper will primarily focus on the latter. For Heidegger, health can be described in a way as the fullest humanity, free to pursue all the possibilities of life with the widest possible openness toward the world. It is not an object of direct attention but rather a background condition that makes one meaningfully engage in daily activities and concerns.

Why, then, should health be discussed together with illness rather than in isolation? There are several reasons. First, health is essentially an inconspicuous and transparent state: it is an unobstructed mode of existence which makes its underlying structure difficult to discern on its own. Illness, by contrast, interrupts this transparency and thereby functions as a methodological resource for phenomenology. It creates a distance from the natural attitude and makes room for reflection [4]. Second, illness is not merely opposed to health but inseparable from health in the latter’s definition. Without contrast to illness, the notion of health would remain inarticulate. Since every human life involves inevitable experiences of illness, health can be understood as negotiating and overcoming such disruptions.

3.  Illness as unhomelike being-in-the-world

For Heidegger, human existence (Dasein) is always a kind of being-in-the-world. Dasein never encounters objects in isolation but always perceives them within a network of significance, in which things appear as instruments to ongoing projects. The world discloses itself not merely as a collection of entities but a network of significance which offers a range of possibilities for human action. When a tool suddenly malfunctions—for example, a hammer is broken in the middle of use—it withdraws from the transparency of everyday activity. The disruption shifts the way of perception, so the hammer becomes conspicuous. It is no longer merely “for” hammering but something whose being now demands attention. Practical engagement is interrupted, and the way the world appears to Dasein is altered.

The same holds true when it is not the hammer but the hand itself that fails. The body, like equipment, can be understood as a constituent part of the structure of significance through which the world is disclosed. Where the boundary between “body” and “tool” is drawn is less a matter of biological fact than of what role a human body plays in a person’s existential engagement with the world. When what fails belongs not to the world’s domain but to the very domain in which the self undertakes its projects, the disruption is experienced as illness. In illness, the body appears as alien, as a damaged tool that resists one’s will and undermines one’s capacity for acting. Yet unlike other tools, the body is not external to the self but inseparable from its very capacity to project possibilities. Hence, illness does not merely disable particular functions; it discloses a fundamental vulnerability at the core of Dasein’s being-in-the-world.

Heidegger initially introduced the concept of “unhomelikeness” (unheimlichkeit) to describe existential anxiety. It is the awareness that human existence is finite, that an individual must face death alone, and that everyone bears ultimate responsibility for her choices [5]. Human existence, as Heidegger points out, is characterized by a persistent sense of unease and disquiet. These states stem from the necessity of confronting the finitude and contingency of one’s own being. This existential anxiety often becomes manifest in illness, where the individual must confront the fragility of the body and the inevitability of death [6]. Illness can thus be understood as a related but distinct unhomelike mode of being-in-the-world [7].

While existential anxiety directs reflection toward the ultimate conditions of existence, illness foregrounds the everyday structures of life, which now become difficult, painful, or obstructed. In health, the body typically recedes into transparency, sustaining a background trust that allows Dasein to dwell in the world fluidly. Illness disrupts this familiarity. While being ill, the body becomes obtrusive, ordinary tasks collapse and demand effort, and daily life is paid attention to. To be ill, then, is to experience estrangement within one’s own embodied existence. It is to experience vulnerability, mortality, and the disrupted flow of ordinary life.

4.  Advantages of the heideggerian approach to health and illness

Understanding health and illness as attuned modes of being-in-the-world demonstrates multiple advantages in both the depth of explanation and the relevance to reality.

First of all, this view explains why most of us, despite having some minor physical imperfections such as tooth decay and myopia, do not consider ourselves “sick”. This is because these conditions have not truly disrupted the overall coordination between one man and the world. Heidegger’s ideas explain why such physical defects are often overlooked: the body can still function as usual with these problems unsolved. The body continues to serve as a transparent medium through which people connect with the world, which makes daily actions and intentions to go smoothly. In this sense, health is not a perfect and static physiological state, but a way of being that makes people engage in various tasks [8].

Second, Heidegger’s approach indicates that even in a “true” disease context—such as disability or chronic illness—individuals do not necessarily feel that they are in a typical “sick” state. They can still interact with the world in a familiar and meaningful way. Initially, people who are partially paralyzed or suffer from chronic diseases may be able to interact with the environment even though the interaction can be severely disrupted. However, as time goes by and they gradually adapt, they might establish a new model of living in the world “homelikely” by using assistive devices, adjusting their daily lifestyles, and redistributing tasks. In such a process, they regained a sense of coherence and familiarity with the world, making their existence in the world once again have the meaning of “home”.

In addition, this approach also indicates significant ethical implications. It challenges the traditional stigma associated with illness by emphasizing that physical changes do not prevent the possibility of a meaningful life. Even when one is ill, one can still create a way of existence that coexists with the world. This perspective affirms that Dasein has the ability to cultivate new models of participation and lifestyles. Therefore, patients are no longer merely passive medical subjects, but rather active shapers and practitioners of their own ways of existence in the world.

Lastly, this method is also significant for clinical practice. It shifts its focus from merely correcting physiological disorders to supporting patients by relocating themselves in the real world and interpersonal relationships. Therefore, rehabilitation should not be merely regarded as a process of restoring physical functions, but rather as a way of rebuilding or creating new ways to connect with the world.

In short, understanding health and disease from Heidegger’s perspective is instructive for both the fields of medicine and philosophy [1]. At the medical level, it not only promotes the improvement of scientific and clinical skills, but also emphasizes people-oriented care, paying attention to the way patients live and exist in the world. At the philosophical level, this perspective has opened up a new path for a deeper understanding of the human condition from the perspectives of society and existentialism.

5.  Limitations of the heideggerian approach to health and illness

Although Heidegger’s framework offers a highly persuasive explanation for health and disease - that is, they can be understood as attuned modes of being-in-the-world—problems arise when people attempt to define clear standards for these states. If health is understood as maintaining the greatest degree of open contact with the world, this ideal state is actually rarely fully realized in daily life [9]. Even healthy people often encounter various distractions: minor discomforts, occasional cognitive errors, or situational restrictions—all of which reduce possibilities and hinder transparent communication between people and the world. This reveals a key limitation of Heidegger’s method: To what extent and for how long must a person undergo destruction before being regarded as residing in the world in a way that is “not being at home”?

Imagine a person suffering from intermittent chronic mental illness. On some days, the symptoms may only slightly impede attention and movement, making the task slightly difficult but still achievable. On other days, mental confusion may seriously disrupt one's work and social activities. The question is: When are these restrictions considered illness? Must this kind of destruction be continuous, comprehensive and profoundly affect a person’s existence? Similarly, emotional fluctuations such as fatigue, anxiety and depression, although they may temporarily reduce the possibilities of life, do not necessarily constitute true diseases. Heidegger’s analysis reveals the qualitative difference between health and disease, but fails to provide a clear criterion for distinguishing “ordinary interference” from “truly unhomelike being-in-the-world”.

Moreover, the social and practical aspects of the disease make the problem even more complex. In human society, the definition of disease has descriptive and practical significance. This definition determines who is eligible for care, and who qualifies for exemption from liability and even financial assistance. Therefore, when the boundary between health and disease becomes blurred, there will be inevitable confusion in social practice.

The differences in culture and environment further highlight this ambiguity. What is regarded as a destructive restriction in one culture may be considered adaptable, normal or even insignificant in another context. From this perspective, whether or not feeling being at home depends on specific conditions such as the environment, duration and intensity [10].

In conclusion, although Heidegger’s approach profoundly reveals how disease alters the way one inhabit the world, it still fails to answer a fundamental question: Where exactly is the boundary between health and disease? How many restrictions are needed to make the world “not like home”? And how do these boundaries interweave with the social, cultural and practical aspects of health and disease?

6.  Conclusion

Over the past decade, scholars have increasingly drawn on Heideggerian approach to explore how illness reshapes not only the body but the very structure of Dasein. A disease such as cancer cannot be understood merely as a biological dysfunction of an organism; it also transforms one’s relation to space, time, embodiment, and others. In other word, it alters the original way one inhabits the world in a meaningful way and may urge one to look for a new way to engage with the world.

In this light, health and illness are not opposite states but rather dynamic modes of being-in-the-world. Health may be understood as the capacity to act meaningfully and responsively within one’s bodily and existential conditions, while illness disrupts such homelike being-in-the-world by disclosing its fragility and finitude.

Such perspective of illness offers theoretical and practical advantages. It helps to explain why those (or most of people) who live with minor ailments do not actually feel ourselves in illness, and how people with disabilities and chronic diseases can reestablish another homelike being-in-the-world. Also, such perspective provides insight in ethical and clinical practice because it emphasizes the dimension of the engagement with the world of the patients and stresses the possibility of actively change and create new narratives for themselves.

Yet this Heideggerian framework has its inner drawback. By emphasizing the existential dimension of illness, it leaves unclear where the boundary between health and illness lies. And this conceptual ambiguity may lead to real social and practical implications.