Illness, in its various forms and intensities, is something we have all, no doubt, experienced and, no doubt, have all disliked. So having a title that speaks of 'Putting Illness in its Place' might suggest that I have found a place where it can be put so that we need have nothing more to do with it. A sort of reversed Pandora's box. However, this is not my aim. If anything, my aim is quite the reverse. I want to explore the idea of illness as a beneficial biological phenomenon and to consider giving it a more significant biological role than it currently enjoys.
Reason
However, before I start, you may be wondering why a biologist such as myself should be interested in illness – or indeed any medical concept. Although medicine and biology have certain similarities, usually they are separate enough that the one does not worry about the concepts used by the other. The reason for my interest is quite straight forward.
I am increasingly finding that biology as an academic discipline is becoming concerned with things that were previously considered to be the preserve of medicine. It is not that the two fields are getting closer; rather it is that medical topics are entering biology. There are, perhaps, two main reasons for this: one intellectual and the other more pragmatic.
Over the last decade and a half, for example, evolutionary (originally Darwinian) medicine has emerged as a serious scientific discipline. To cite what is perhaps the most commonly used definition, '[evolutionary or] Darwinian medicine is the enterprise of trying to find evolutionary explanations for vulnerabilities to disease'. In this respect, rather than being simply concerned with the currently prevailing (or proximate) human condition, evolutionary medicine is concerned with what has gone into making us what we are and into making our situation what it is. This includes trying to explain our medical problems and trying to inform best practice accordingly.
As originally envisaged, evolutionary medicine was to be a way of applying the ideas of evolutionary biology to clinical medicine. It still is. However, the greatest enthusiasm for evolutionary medicine has not come from the medical profession but from those already engaged in the study of humankind from an evolutionary perspective: biological anthropologists, human biologists and the like.
That was the intellectual reason; the pragmatic reason is that at the same time as the emergence of evolutionary medicine, there has been an expansion of higher education – at least in the UK – where somewhere in the region of 40% (I think it is) of school leavers are now undertaking degree level study. One of the most popular areas of study at this level is that of health – even when the student has no career aspirations in that direction. One finds that those of a more humanistic leaning do courses in 'Health Studies' whereas those of a more scientific leaning do courses in 'Health Science'. At the same time, 'Sports Science' with its emphasis on fit and healthy bodies also attracts large numbers of students. Biologists are among those who are now called upon to teach on such courses.
Thus, one finds people who are not medically qualified having to address things that have traditionally been considered to be the objects of medicine. Here, there is none of the vigorous debate about biomedical concepts found elsewhere. Instead, one finds rather imprecise, ordinary language being used. A precise understanding of terms like disease, health and illness, has not, so far, been derived or arrived at scientifically. This makes for potential difficulties and ambiguities when using these terms. For example, the words 'illness' and 'disease' sometimes get used interchangeably. Similarly, so do 'disease' and 'pathology'. This leads to the following syllogism which must surely be false:
if illness = disease
and disease= pathology
then illness = pathology
[A false conclusion due to one or more false premises.]
The problem is how to rectify this situation. How do we arrive at a more precise scientific usage of those terms that are currently being used so imprecisely? There is, of course, the existing debate about such terms as 'disease' and 'health' but rather than simply entering this, predominantly humanistic, debate mid-flow, I believe that to gain a scientific account of such concepts, we, as biologists, must undertake our own form of conceptual analysis. We must not rely upon medical usage and we cannot simply adopt the ethical or humanistic formulations currently found in the philosophy of medicine. We must find our own understanding that suits our own particular world view. (Even if this makes for ethically unpalatable conclusions.) That is not to reject what others have to say or to ignore what can be drawn from what has already been presented and debated. There is much valuable thought we would do well to draw upon – but this we need to interpret in our own terms.
However, this leaves one with the question of how we are to begin such an enterprise.
How?
The approach I believe biologists should not take is that of starting by trying to define for themselves what disease and health are. Instead, I believe that we should begin with illness.
This may sound surprising. After all, if biology is concerned with the substance, organization and processes involved in biological entities – including those associated with our own bodies – then one might have expected me to have suggested a more physical – that is, anatomical, physiological and/or pathological – approach probably focusing on ideas not very different to those found in Christopher Boorse's biostatistical theory. However, this would be to limit biological interpretation; it would overlook a host of different forms of biological explanation.
There is much in biology that is not about substance, organization or process. There is much which is not tangible and which cannot be quantified in the usual scientific sense. There is what might be considered to be a qualitative dimension to biology. This is expressed, not least, in the area of evolution. While the survival of numbers of individuals can be quantified, what ensures the survival of one individual rather than another has much to do with the differential quality of those individuals in relation to each other, the habitat in which they live and, it must not be forgotten, pure chance.
I started by stating, rather deliberately, that '[i]llness, in its various forms and intensities, is something we have all, no doubt, experienced and, no doubt, have all disliked.' Here, I have made two universal statements when I suggested that we have 'all … experienced' and 'all disliked' illness and, to add emphasis, I even used the phrase no doubt twice! Making such universal statements and claiming that there is 'no doubt' is something that philosophers usually find inherently unacceptable. However, on this occasion, in relation to illness, I suspect that they would be more accommodating. And yet, in a biomedical context, illness is frequently treated as being of secondary importance.
Why start with illness?
If we consider a typical medical consultation, the clinician will ask the patient how they feel, if they are in pain or discomfort and, if so, where that sensation is localized etc. In light of these subjective impressions, the clinician will go on to seek explanations for these experiences in more objective terms. Various anatomico-physiological parameters will be investigated for what they can add to the diagnosis.
In this scenario, illness is merely the subjective experience which leads a person to consult their doctor. Thereafter, it largely recedes from view as medical investigations aimed at obtaining more objective data take over.
Various definitions of illness have appeared in the philosophical literature. These, I think it is correct to say, have drawn largely similar conclusions. The definition given by Marshall Marinker (1975) perhaps allows us to explore some of the background to the clinical context. And see how starkly this differs from a purely biological perspective. Marinker defined illness as:
'Illness … is a feeling, an experience of unhealth which is entirely personal, interior to the person of the patient.'
He goes on to add '[o]ften [illness] accompanies disease [which Marinker defined in a somewhat pathological sense, elsewhere in the same article] … Sometimes illness exists where no disease [that is, pathological process] can be found. Traditional medical education has made the deafening silence of illness-in-the-absence-of-disease [again meaning a pathological lesion] unbearable to the clinician. The patient can offer the doctor nothing to satisfy his senses – he can only bring messages of pain to the doctor, from an underworld of experience shut off for ever from the clinical gaze.'
This, he goes on to state, causes the doctor (rather than the patient) some distress which usually results in a resort to, what he calls, vague 'psychiatric language'. From what Marinker has to say, it almost sounds as if the doctor is in greater need of his own profession help than the patient.
Marinker also goes on to add:
'The advent of the behavioural sciences in the curriculum of the undergraduate may help him to understand the nature of … [the] dialogue between doctor and patient, but they do not pierce the silence and so they cannot frame for the doctor a meaningful reply.'
This 'silence' which cannot be pierced by the application of the behavioural sciences is that of having nothing to satisfy the doctor's senses; no way of directly accessing the patient's subjective experience of illness. The emphasis here is clearly on the doctor's problem with verifying the genuineness of illness rather than the patient's problem of feeling ill.
This is, in part, why I suggested earlier that biologists should go their own way and not simply rely upon medical usage. There is a sense in which illness is a very human thing but not a very medical one.
Importantly, what Marinker sees as a problem for the medical profession is quite the reverse biologically. The key feature of illness is undeniable: it is an entirely subjective experience. It is literally part of our being aware of ourselves. This is part of being biologically human.
Although it may be impossible to know what others are experiencing, it is not unreasonable to assume that others also experience this entirely personal, interior feeling called illness. Indeed, by virtue of its very subjectivity and because we have all experienced this feeling at one time or another, we have a more direct appreciation of what illness is than perhaps any other biomedical concept. If somebody describes a feeling associated with illness, one may be able to say that one has had the same or a similar experience; one may, therefore, be able to empathize. However, if somebody were simply to say that they had 'such-and-such disease' without adding how it felt, one would be much less likely to be able to identify with this. Experience here is central. Yet, as I have already said, illness seems to be given something of a secondary status precisely because of this.
Biological existence is typified by a daily struggle for survival. A key factor which influences how we go about this is how we feel in ourselves – not our knowledge of our anatomico-physiological processes. Knowledge of the interior of the body is a recent thing. We could not look inside the living body until Roentgen discovered X-rays at the end of the nineteenth century and it was not really until the last few decades that various other forms of medical screening have become commonplace for the more fortunate.
All that most humans still have to go on in the daily business of survival is how they feel. How one feels has numerous effects. It influences whether we are active or choose to get more sleep; it influences whether we eat or not, what we eat and how much; it influences whether we make ourselves warmer, cooler etc. These and a range of other experiences of our own bodies all contribute to ensuring our individual survival.
We all know what the experiences of hunger and thirst are like and what it is like to be hot or cold. We may not be able to provide a complete verbal description of these experiences; we may not be able to describe, for example, what thirst is like to a fish (who, spending all its life submerged in water, is rather unlikely to have any such notion) but we all know what thirst is like. Likewise, we all know what it is like to be hungry, to be hot, to be cold and to be ill.
Furthermore, we also know that these feelings require of us a response so that these feelings can be nullified. The implications of feeling hungry or thirsty are that one must adapt one's immediate behaviour with a view to satisfying these needs – one must obtain food and drink. Similarly, one must also ensure a comfortable body temperature by cooling or warming oneself (indeed, we rely more on behavioural means of maintaining a comfortable body temperature than on physiological mechanisms such as sweating and shivering). Not satisfying these feelings may result in one becoming not just undernourished or dehydrated, too hot or too cold, but increasingly distressed physically and mentally. This can be to the detriment of the individual and, in extreme cases, can even lead to death.
Canguilhem's problem
In 1943, the medically trained French philosopher, Georges Canguilhem, posed an important problem that continues to be relevant to this day. Take a man, he suggested, who complains of no ailments and whose life is suddenly cut short by being murdered or dying in a car crash. For various French legal reasons, an autopsy is performed and the dead man is found to have a serious cancerous tumour – in Canguilhem's example, of the kidney. The point of the story is to ask, what are we to make of the man – did he have a disease or didn't he? Answering this question is not simple. Fortunately, this is not my aim today.
However, I would like to look at the problem in a slightly different way to that in which it is usually considered. A less frequently explored dimension to Canguilhem's problem is revealed in looking at the man's experience of life and asking whether it was, in terms of its biological outworking, impeded in any way. The answer to that question is quite straightforward: there was no such impedance. The man felt fine; he was unaware of any (literally) ill-effects from the tumour; he got on with life as usual.
If one takes a medical perspective where there is particular emphasis on lesions – irrespective of whether they give rise to symptoms at an experiential level or not – one certainly finds that the dead man had a lesion that would cause a clinician concern. Frequently these days, medical screening brings to light asymptomatic lesions of this sort. (Indeed – and with some relevance to Canguilhem's problem – just a matter of weeks ago, a famous Manchester-based figure in the British entertainment business died of the effects of a kidney tumour having first had it discovered during its asymptomatic phase on routine screening about a year ago.) Nowadays, individuals with these lesions are frequently labelled medically as 'diseased' without the need for the traditional step of having first experienced any overt illness associated with these lesions.
However, biologically, any individual who is not ill is one who is potentially able to go about the daily business of individual survival and performing reproductive acts. These are the two biological imperatives for which every higher organism seems to be innately geared. The man in Canguilhem's problem was able to do all that was necessary to perform these biological imperatives.
Towards a bigger biology of illness
By starting with illness, rather than disease or health, biology can seek not only to define what illness is, it can seek to understand it in the broadest of senses. 'What is illness?' is not just a question about which physiological processes are involved or how these are interpreted by the brain as negative feelings. Biology can ask 'Why is there illness at all?' If illness has not been lost through natural selection, does it offer the individual something in terms of survival advantage? Indeed, the very commonality of illness – its being a fundamental human characteristic that all seem to share – is in need of scientific explanation. Why have we evolved as organisms with the ability to feel ill?
The lack of overt illness – even in the face of a potentially serious lesion – enabled the man in Canguilhem's problem to continue with life unhindered. So one might have assumed that actually feeling ill would tend to impede one's capacity to survive and to reproduce and, therefore, run contrary to the basic tenets of evolutionary biology.
That we have an ability to experience illness and that this hasn't been lost through natural selection suggests that there is greater reproductive advantage to be had from the ability to be ill than otherwise. Illness appears to offer a reproductive advantage.
Before going further, perhaps the idea of reproductive advantage needs a little clarification. By reproductive advantage, I refer here to the relative success of individuals at producing offspring. An individual that produces more offspring relative to another can be said to have a reproductive advantage. Those offspring will, of course, resemble their parents in sharing many of their inherited characteristics. Sometimes, one says that the former has a greater biological fitness in comparison to the latter. The ability to produce offspring does not only depend on the state of a person's reproductive system, it can be a product of the quality of the individual as a whole organism. Also, the longer an individual is able to stay alive – the longer that individual is able to survive – the more opportunities there will be to engage in reproductive acts and the more opportunities there will be to produce offspring. So, having the quality of being able to stay alive longer, can have reproductive consequences. (Here, I am, of course, talking in general biological terms; clearly humans now exercise greater reproductive choice but this was not the case during our evolution.) The point is that a mechanism which helps an individual live longer inherently contributes to potential reproductive advantage.
The question that follows from this is 'Does illness contribute to one's life in this way?' – that is; 'Does illness have an effect that can lead to a prolongation of life and so to reproductive advantage?' Unfortunately, I cannot answer that question categorically since the necessary work hasn't been done to test this idea yet but my guess would have to be 'Yes'. The following example certainly points in that direction.
The importance of illness – The example of pain
Consider pain. This is sometimes an aspect of illness; it is certainly one of the ways in which we experience ourselves and, in response to it, we certainly modify our behaviour to ensure continued survival.
At a human level, pain is something that most people dislike intensely. This, in fact, is its most important feature. Without pain, strange as it may seem, life is virtually un-liveable.
There are people who do not have the ability to experience pain – the condition is known as congenital insensitivity to pain or congenital analgia. Rather than being the lucky ones who live a comfortable life devoid of the aches and pains that we may dislike and grumble about so much, they are among the least fortunate for they tend to die much younger than the rest of us.
In those who have no sense of pain, injuries – from tiny cuts and scratches to serious bony fractures – all go unnoticed. One typically finds damage to the tissues of the mouth. Lips may be bitten unwittingly; the tip of the tongue may even be bitten off as one chews one's food. The cornea of the eye is easily damaged by grit that gets blown in and not got rid of. Infections can also go unnoticed.
The situation has certain parallels with leprosy. It was once commonly believed – and may still be believed by some – that the infective agent in leprosy (Hansen's bacillus) caused the infected person's flesh to rot, thereby giving the characteristic effects such as loss of fingers, toes etc. However, this is not the case. In leprosy, there is a loss of peripheral sensation which tends to result in injuries and wounds going unnoticed and lasting damage occurring because immediate remedial action is not taken.
In these examples, it is striking how severe the effect of supposedly minor injuries can be. Indeed, even failing to relieve the pressure on one's tissues brought about by sitting or lying too long in one position can lead to pressure sores (or what used to be called in British hospitals 'bed sores'). The elderly and frail can be particularly susceptible to these lesions which, if left untreated, can lead to severe tissue damage and even prove fatal.
If in medically advanced societies, those with congenital analgia die relatively young, a life without pain in the worlds inhabited by our ancestors – the worlds in which we literally evolved – would have been impossible. There the ability to experience pain was necessary for survival.
So, if the ability to experience pain is advantageous, then there is a strong suggestion that the ability to experience illness may also be advantageous.
If those who are unable to notice minor injuries fair so badly, conversely those of us who are flourishing must be attending to ourselves rather well – albeit unwittingly. It appears that we are constantly monitoring ourselves at conscious and non-conscious levels and constantly responding to how we find ourselves to be. The lesson we learn, especially from those who cannot do this so well, is that constant self-monitoring and response is essential for individual survival.
A significant feature to note about this is how it seems to occur at both conscious and non-conscious levels. Even when we are asleep, there is something about us that is aware – if not awake. In our sleep, we shift our body positions as need arises. Failure to do so can lead to the pressure sores mentioned earlier. If this self-monitoring occurs at both conscious and non-conscious levels, this suggests that illness might not be a simply conscious phenomenon. There may be sub-conscious or non-conscious aspects involved too. Indeed, there may be a lesson to be drawn from animals.
This sense of monitoring oneself is certainly not confined to human beings with their elaborate sets of mental attributes. Matthew Kluger (at the University of Michigan) found that when experimentally infected with aeromonas hydrophila, fish actively sought out warmer parts of their tanks and lizards warmer places in which to bask. These animals cannot raise their body temperatures in order to combat infections as we can; they have no fever mechanism. If there is a need to alter body temperature, they must rely upon behavioural responses. By seeking out warmer places, the fish and lizards were able to raise their body temperatures artificially and were found to combat these infections more successfully than those kept confined to cooler surroundings. Furthermore, it has been suggested that even insects, when exposed to certain fungal infections, respond by seeking out warmer places too. Thus, there appears to be some sense of self-awareness involved even in creatures with very limited intellectual capacity.
The important point here is that this 'feeling, [this] experience of unhealth which is entirely personal, interior to [one's] person' (to refer back to Marinker) is not confined to human beings. There is something in the way animals are constructed as complex systems that contributes to self-preservation, to individual survival. These require mechanisms for conscious and non-conscious self-reference. Given that something like this is present in fish and lizards, one may perhaps surmise that this is, in evolutionary terms, a very old and fundamental mechanism and that our sense of illness may be an experiential extension of this more basic capacity.
An interesting feature about the experience of illness is that it can be over-ridden to a certain degree. Even when we are feeling ill, some sudden urgency may make us leave our sickbed. If our illness is not too debilitating, we may have sufficient capacity to temporarily leave our sense of illness behind and respond to some more pressing matter that may be threatening our survival. That there is a means whereby illness can, in effect, be over-ridden suggests that illness is something other than what simply results when things go wrong with our physical bodies; it appears not to be simply what results from some accumulation of problematic organismal events which then happen to reach conscious level. Illness appears to be something more organized or co-ordinated than this.
What is Illness?
If, at this point, we briefly return to the question 'What is illness?' we will find that Marinker's definition, although in keeping with other such definitions, is not very specific. When he says that '[i]llness … is a feeling, an experience of unhealth which is entirely personal, interior to the person of the patient', we have to ask what feelings in particular? Is there a particular feeling that is illness or is illness a composite or constellation of a number of different feelings? For example, I considered pain earlier. Is pain entirely distinct from illness or do illness and pain intersect or overlap in some way?
There are a number of experiences that one can say are associated with illness. This list may be worth considering – although it is not intended to be complete:
General malaise
Looking for a term that might best describe illness, I came across this one. It means simply a general sense of unease. It may not actually describe illness but it may serve as an alternative form of expression.
Tiredness
… is a common characteristic of illness. We might think that this comes about due to a lack of energy but this is unlikely to be the case.
Loss of libido (in both senses)
There are two senses to the word libido – the more commonly recognized sense of sexual drive and the less commonly used sense of a 'will (or urge) to go about living'. Loss of libido parallels 'tiredness' to some extent.
Loss of appetite
This can be envisaged as a deliberate physiological mechanism. During an infection, loss of appetite can serve as a way of preventing certain substances that the infective agent needs to flourish from getting to it.
Bodily discomfort or overt pain
We have already considered this to some extent. Aches and pains and feelings of discomfort are sometimes localized and associated with the site in the body where attention is required. However, this is not always the case. Appendicitis, for example, commonly begins with discomfort in the centre of the abdomen rather than over where the appendix is situated.
Fevers/Chills
Changes in the way the body regulates its temperature are an aspect of illness. Again, we have already touched upon this.
Gastro-intestinal 'awareness' ('hyper-awareness')
Especially if something we have eaten is a potential source of harm, the gut will react to propel it out – either more rapidly in the usual direction or by vomiting in the opposite direction, in which case, this is usually preceded by a sense of …
Nausea
… the feeling that we are going to vomit.
Headache
Just having a headache can be enough to make somebody say that they are unwell or ill.
Sensitivity to light (photophobia)
One may wish to avoid light and rest in a darkened room.
Visual disturbances (aura)
Here I am thinking more specifically perhaps of migraine where during these intense headaches, visual disturbances in the form of different patterns of light etc may be experienced.
Auditory disturbances (tinnitus)
One may experience a ringing or whistling sound. (It would not be strictly correct to call this 'ringing in the ears' as, although it may be perceived as coming from or being in the ears, what causes the experience may not actually originate there.)
Disturbance of balance/sense of imbalance
Where one does not feel comfortable in an upright position or changes in posture lead to exaggerated feelings of motion, or there are feelings of motion when one is, in fact, still.
However, no one of these on their own is illness per se nor do we have to experience all of them in order to consider ourselves as being ill.
However, although it appears that illness is a feeling that is difficult to identify precisely, it also appears that it can exist in combination with one or more of the other, more specific experiences listed above.
This is an interesting finding in itself. Hunger and thirst are not like this. Neither, it appears are feeling hot or cold. Each of these is a quite distinct feeling signalling a specific need. Illness, on the other hand, appears to be both combinable with other negative experiences and to be something in its own right; it can signal that attention to a specific part of the body is necessary and it can signal a more general, non-specific (perhaps whole organism) need.
If I am on the right lines here, I think it reasonable to suggest that this, perhaps, highlights and emphasises the significance of illness as a biological phenomenon that has evolved as an aid to our individual survival.
Conclusion
Thus, I would like to suggest that illness – that subjective experience we all dis-value so greatly – has an important biological role. What we dis-value experientially is beneficial biologically. Without it, we might not be able to survive; certainly not as well as we do.
That one can be ill at all is, in a sense, a positive sign. If we could not feel pain, if we could not feel hunger or thirst, if we could not feel too hot or too cold, or any of the other experiences that contribute to the way in which we go about ensuring our individual survival via behavioural modifications, we would be more likely to perish.
Furthermore, perhaps we should find ways of responding constructively to illness and not merely try to block out its message. Perhaps actually being ill should be construed in a positive light. There may even be scope to consider illness as a dimension of health. Being ill may be the out-working of a health-enhancing reaction in that it brings about responses which can lead to a return to optimal activity.
Perhaps, to be healthy, a person must have the ability to feel pain amongst a range of other experiences. In short, to be healthy – or at least maintain a healthy state – a person must be able to feel ill and suffer in various ways.
The impression I have given of illness may be unlike descriptions that appear elsewhere. I am not concerned about illness in terms of welfare issues as they relate to humans – or indeed to animals. I am concerned about illness as a fundamental biological phenomenon in its own right; a phenomenon which has a bearing upon the way the individual responds to his or her different bodily states and the effect this has on the survival chances of that individual. Because it has been seen as an experience to be dis-valued and avoided and because it has only been allowed a limited medical role, illness has not yet been adequately explored or fully appreciated – at least not, I believe, from a biological perspective.
And so, by way of a reference to what I believe to be the importance of illness as a form of self-monitoring, or self-awareness (in all its various forms) and remembering the problems doctors have with other people's illnesses, let me conclude with this quotation:
'In the end, one only experiences oneself.'
Friedrich Nietzsche
Acknowledgements:
I would like to thank the trustees and fellows of the Konrad Lorenz Institute, Altenberg, Austria, where, as a Visiting Fellow, I was able to develop the ideas expressed here. I would also like to thank Annette Lewis for her help in the preparation of this transcript.