What Is Health?

What Is Health
Most of us think we know what health is, but we are actually more attuned to what it is not. We readily appreciate that health does not, for example, entail pustules, swelling, listlessness, or vomiting, and the term generally excludes states that stem from injury or result in death.

There are features of one’s countenance and behavior that provide diagnostic clues about physical wellbeing--like the swolen capillaries in the nose and cheeks of a man with high blood pressure--and, of course, medical professionals have devised countless tests to evaluate our operational status, even when other symptoms are ambiguous or absent. But do we really know what health is?

In this series, I will explore what health really is, for only in truly understanding our health can we act to maximize it. To understand anything complex, we need precise definitions and a body of theory supported by observation. One would expect these criteria to have been met by our health authorities, but there is more confusion than clarity, even in the professional sphere.

A few authors have pointed out the obvious concerning our definitions of health, but their voices, while relevant, are few and obscure (e.g., Sartorius, 2006; Brüssow, 2013).

The World Health Organization (WHO), defines health as a

"State of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity."

Just read that again and soak in the utter vacuousness. What kind of facile characterization is this? The definition lacks any substance that would make it at all informative, yet this intellectual combover has served as the world's bookmark for referencing health since WHO's founding in 1948!

Bad definitions deserve a proper snuffing and burial:

First, WHO's definition refers to three different states: physical, mental, and social, as though these domains are on equal footing—are they really? Rather, it seems, they are nested in a causal hierarchy, each contingent on the level below it. Social health is a sub-function of mental health, which is contingent on physical health, which depends entirely on environmental health. Is this not obvious?

Second, the definition hinges on the term “well-being,” a word that is too subjective to be of any use. Fundamentally, the term means feeling well, but health is much more than a perception. Health has a physical reality that is minimally monitered by your consciousness. The reality of a headache can be described at molecular, cellular, tissue, or system levels, none of which derives any meaning from the term wellbeing. The term lacks any detail at these levels of analysis because wellbeing is the result of health, not part of its description.

Finally, WHO's definition adds an extra layer of confusion by informing us that health may or may not be the very things that usually come to mind when we think of health.

In future posts, I will discuss at length the distinctions and interactions between the different domains of health, but, for now, I will (for emphasis) repeat confidently that social health is entirely contingent on mental health, which absolutely depends on physical health, which hinges utterly on environmental health. I will, of course, defend these assertions in this series, for those who do not readily see the nesting relationships.

Surely other health authorities have done better than WHO, right?

Sadly, no.

Perhaps the best widely recognized definition of health is that of Georges Canguilhem from his 1943 book, The Normal and the Pathological: "health is the ability to adapt to one's environment" (The Lancet, 2009), . This definition is still too vague, and for the same reason that WHO's definition fails, but it is a step in the right direction. Adaptation is a feature of functioning biological systems, not a description of dysfunction in them. Adaptation relates to health in that when biological systems are functioning properly (healthy), the organism is maximally adaptable to the normal range of environmental changes. If, however, the environment becomes too cold, too hot, anoxic, or acutely toxic, health immediately diminishes.

There are many questions one might ask to highlight the inadequacies of widely-used definitions of health. For example, how does mental health differ from physical health? Does mental health involve only the operation of the nervous system or are other organs (or organisms!) involved (see Brüssow, 2013)? What is social health, and is it different for introverts and extroverts? How are the domains of health interconnected, or are they independent in some ways? Is health, like beauty, all in the eye of the beholder? Is health a relative term, with different meanings for different individuals, cultures, or species?

Some people think that health is relative, but it is so only in a trivial, perceptual sense. Perceptions of health are relative, but health (the process) is not. It is certainly possible for people to percieve that they are healthy when they are not, or to deceive themselves and others about their health, but that does not make health relative in any physical sense. Health is a measurable, quantifiable state that has continuity through time. The fact that we cannot yet measure or quantify it properly does not make it relative, just complex.

Health evolves over the course of our lifetimes and this historical feature makes health seem relative, but it is certainly not relative in the sense that it varies on any dimension governed by opinion.

Here is a definition that gets close to the heart of matters:

"Health is a dynamic state of wellbeing characterized by a physical, mental and social potential, which satisfies the demands of a life commensurate with age, culture, and personal responsibility" (Bircher, 2005).

This definition almost captures the idea that health is a state of optimal functioning of a specific system (an individual) in its present configuration. If this were not true there could be, for example, no healthy aging and no healthy amputees.

It is no wonder we are in a worldwide health crisis, we can't even get a straigh answer about what health is from our health authorities. The intention of this blog is to explore and find answers, to point out misconceptions and errors, and to help reorient current thinking and point out the neglected obvious.

We are beings whose health can be optimized at any given time during a long progression of functional competence that begins at conception, peaks in young adulthood, and declines for many decades thereafter. We have little control over the initial conditions, but we have some influence while we are young, and complete responsibility when we are older. Yes, our health is our responsibility, not some health authority's, so it is important that we focus on reality.

For example, whether you know it or not, there is chemistry behind anger, love, and jealousy. Chemistry is the foundation of thought, emotion, pain, pleasure, intelligence, and everything else our brains do. The love of music is chemical, but not merely so. It is also structural (epi-chemical), relying on the complex process of biological development to tune the nervous system that responds to pitch, tempo, and melody. Yet all of these structures are entirely governed by chemistry. Some people are transported to great emotional heights by music while others experience it without passion. All chemical!

Since I am an evolutionary biologist, I will, of course, discuss health in the context of biological history, an approach that is often overlooked, perhaps avoided. But I recognize that there are other valid ways of conceptualizing the topics I discuss. Be it known that I do not seek to invalidate metaphysical explanations of physical being. That is not my aim. I wish only to draw attention to things we can observe, things which help us interpret our strange and wonderful (sometimes terrifying) circumstances.

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A Useful Definition of Health
I define health as the optimal functioning of a complex, integrated system capable of homeostasis in a circumscribed environment. Such systems are all biological, but I once thought that homeostasis (biological self-regulation) should not be requisite. This omission allowed cars and computers to be described as healthy or unhealthy, but reflection has reoriented my assessment. Reference to the environment is an important inclusion, since living systems require inputs and interactions that regulate health.

The advantage of defining health in this way is that we know how to study optimizable, self-regulating systems. These systems have measurable peaks in the parameters of interest (performance parameters), and they persist under the environmental conditions that fostered them.

Health is a function of systems capable of regulating themselves, given appropriate, persistent, and stable environmental inputs. Good health is a state of operation near the optimum for the system in its present configuration, yet, because biological systems are regenerative, physical constitutions can be improved by maintaining optimal (health-promoting) conditions. Bad health is a functional state that is far enough from optimal to have degradative consequences. Humanity has yet to explore in any detail what optimum means in the context of health. Perfect health is an ideal, especially for very complex systems, but bad health is an unfortunate reality for all at some point.

It is important to recognize that health is not a thing—it has no existence independent of the systems it characterizes. It is a process, or, more precisely, a description of the state of functionality of a set of interrelated processes. A system in good health operates in high congruence with its environment and in accord with its design specifications.

Biological evolution does not require a purposeful designer. Natural complexity results in designs that have a sort of purpose in that they evolve to perform a function. The layers of function build up over vast spans of time until the system wakes up and asks: “What am I?”

Does something have to suffer before we can diagnose it with bad health? No, not at all. Many human conditions considered ill-health are unaccompanied by suffering. In fact, some conditions that result in severe dysfunction are characterized by blissful ignorance of any loss that others might construe. Consider certain cases of Autism or Down’s Syndrome in which the afflicted appears to relish existence. Are these individuals healthy?

As a biologist with a professional background in mental health, I have given these topics considerable attention over the years. This blog will be an ongoing exploration of physical, mental, and environmental health. There is much territory to cover and I anticipate some controversy. As with any exploration, if I don’t learn something, too, the effort is a failure, so I expect feedback from you.

In the next post I will attempt to justify my definition of health and to explore the reasons for adopting it over the popular definition. We have a long way to go, but I am looking forward to the journey. I hope you are, too.



Bircher, J. (2005). Towards a dynamic definition of health and disease. Medicine, Health Care and Philosophy, 8(3), 335-341.

Books, Z. (2009). What is health? The ability to adapt. The Lancet, 373(9666), 781.

Brüssow H. (2013). What is health?. Microbial biotechnology, 6(4), 341-8.

Sartorius N. (2006). The meanings of health and its promotion. Croatian medical journal, 47(4), 662-4.


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