A Picture of Health

On the search for conceptual biological models of disease and health, and beyond

Since we are now to give, as I understand it, at least one seminar each year, I thought that I would use this opportunity to try to give some sense of the problems in which I am interested. As such there may be an element of musing, as I go along, but I shall also introduce some of the things I concluded while on sabbatical – even though there are still gaps and weaknesses.

I should, therefore, begin by referring to my sub–title – which is the descriptive rather than the catchy part of my overall title – and point out that I shall be talking about trying to find conceptual models that help us put the ideas of disease and health into some biological perspective – and why I believe this to be important. To be clear, there are models other than conceptual ones. For example, I will not be talking about descriptive or predictive mathematical models of such things as epidemics or other supposed phenomena – about which I, like others, have certain reservations.

The conceptual models with which I am concerned here relate to disease and health but, as will become evident, the issue goes beyond this. What has become very evident to me is that there is more to be gained from the process of trying to understand these terms than from actually succeeding in producing some form of definition of each and then moving on. When I started this work, my focus was on trying to contribute to the problem of defining what we mean by disease and health but, while this continues to be an element, the work is now done within the context of using disease and health as a lens through which an understanding of something more fundamental can be obtained – that is, trying to understand the idea of the organism.

Surprisingly, the terms 'disease' and 'health' receive relatively little attention as concepts from those who use them most, that is, those engaged in clinical or clinically-related activities. The result is that these terms can be applied in a careless and even cavalier fashion. But what is perhaps worse is that many fail to see that these words even need attention. At times, some in the medical profession object that they can manage well enough without having to worry about precise meanings. This is in stark contrast to the usual raison d'être given for such analysis: that it is central to the conduct of ethical medical practice to have a concept of disease – which, after all, prompts medical intervention – and a concept of health – which prevents intervention or leads to its cessation.

Furthermore, although the terms 'disease' and 'health' are applied primarily to biological objects, there seems to have been very little serious attention given to these terms by biologists. Instead, biologists have been largely content to adopt notions that either diffuse across from medicine or arise intuitively. This is perhaps not surprising if, as I have just said, the raison d'être for such analysis is the conduct of ethical medical practice. The ethics of medical practice is, after all, not central to the conduct of biological science. However, when it comes to trying to understand biological organisms more fully, we must study them under different conditions and in different states – and that includes what we might call 'diseased states' and 'healthy states'.

We are accustomed to the careful laboratory manipulation of physiological parameters and the division of subjects – human and animal – into control and experimental groups and studying the differences that ensue, but we can go further. The so-called environmental physiology pioneered by Joseph Weiner (1915-1982) in the mid-twentieth century included studying subjects in the variety of their native habitats. In so doing, the differences between subjects drawn from different geographical and genetic backgrounds were highlighted and a more complete picture of our species was developed than could have been gained via laboratory approaches alone.

An extension of this – which has been largely missed – is to study organisms in the way the philosopher Imre Lakatos implies when he suggests that …

'[I]f we want to learn anything really deep, we have to study it not in its 'normal', regular form, but in its critical state, in fever, in passion. If you want to know the normal healthy body, study it when it is abnormal, when it is ill.' (Imre Lakatos, 1976)

However, to do this we need to be able to differentiate between such states. It is only through conceptual analysis that we can begin to do this.

At the end of his book 'Talking about Health', in which Lennart Nordenfelt presents a dialogue between a philosopher (who is, in fact, Nordenfelt himself) and an imaginary inquirer, the philosopher states that 'Philosophical reflection never reaches a final goal, and for that reason it must [also meaning can] never cease. Fresh angles of approach always await us, and improvement is always possible when we attempt to answer all the large and difficult questions'. Importantly, he goes on to point out that … '[t]he fact that we never reach an absolute final point … does not mean that we do not make progress.'

A key aim of trying to understand disease and health conceptually then is 'to make progress' in understanding 'from fresh angles of approach' the object to which the terms 'disease' and 'health' are applied. Noticeably, Nordenfelt suggests that 'improvement is always possible when we attempt to answer … the large and difficult questions.' In response to this, one must ask whether our most pressing biological questions are sufficiently large and difficult enough to help us understand biological objects more fully or whether biology as a discipline has become a means to an end in some other agenda.

Conceptual difficulty, to be clear, has nothing to do with technical difficulty – in the sense that special practical skills or specialized equipment are necessary. Because a question is technically difficult to solve does not mean that it is also conceptually difficult. The conceptual framework within which one is working is not necessarily advanced or altered appreciably because the process of coming to a solution involves sophisticated practices.

A conceptually difficult biological question, on the other hand, may be addressed without the need for any special techniques – other than intellectual ones. For example, no biologist has yet given a complete answer to the question 'What is Life?' and no experiment that is likely to answer this question has been proposed only to fail due to lack of technical expertise. Instead, this question has largely disappeared from mainstream biology due, largely, to its conceptual difficulty. We seem now to be able to manage in biology without an answer to this question and so it is left largely to those interested in the possibility of extra–terrestrial life and those engaged in computer–based artificial life, to ponder. Arguably, biology as a science has come to be formulated in such a way that the question of what life is is not allowed to be a 'pressing question'.

But this leaves us, those who call ourselves 'biologists' – people who study life – without knowing precisely what life is. This, in turn, leads to the rather absurd suggestion that if asked what it is that characterizes what we are studying, we ultimately reach a point of having to say that we can not say precisely what it is, but that we know it when we see it.

A similar conceptual difficulty applies to disease and health. As alluded to above, for most in the medical profession the conceptual meaning of disease and health is not a pressing question. This is largely because they think they know disease and health when they see them.

Interestingly, we all seem to know what disease and health are when we see them. That is, until it comes to giving a precise statement of exactly what we mean. It then becomes a much more difficult proposition. To illustrate this, look at this list taken from the BMJ, pick a few conditions at random and ask yourself which you would call a disease – and why? I shall reveal all at the end.

Scientifically, we are left in a rather awkward position – were we to realize it. Scadding (1988), one of the few medical men to have been concerned with concepts of disease and health, noted that …

'Popper points out that essentialist definitions, depending upon intuitive acceptance for their validity, have no place in science.'

An essentialist position holds that not all of an object's properties are of equal signification – that is, some are essential to its being what it is, whereas others are accidental. For example, one might argue that the possession of pages is an essential feature if we are to call something a book, whereas the precise colour of those pages is accidental. The main problem with an essentialist position is that of establishing the grounds upon which to base the distinctions one makes between essential and accidental features. It does not necessarily follow that what one 'knows' intuitively can be easily supported by a rational argument. There are always 'what ifs' to contend with.

When it comes to disease and health, this is much the position in which we find ourselves. Often when comparing examples of conditions that have been medically labelled 'disease', we find no single common characteristic – no essential feature – that all share. Disease seems to defy definition in strictly essentialist terms. The same is true for health. However, at least part of the reason for these difficulties lies, I believe, in the tendency for disease and health to be treated as if they were distinct entities when, in fact, they cannot be said to exist in any sense without being associated with an organism that is usually described as having a disease or being healthy. Both disease and health have become reified – that is, they are abstract concepts that have taken on a more concrete persona. (And I use the term 'persona' for deliberate effect.) Disease is commonly thought of as tantamount to being a circumscribed, measurable entity. This way of thinking has been traced back to, and indeed blamed upon, Rudolf Virchow.

The psychiatrist Frederick Kraupl Taylor – another of the few medical men concerned with concepts of disease and health – notes how 'Virchow … towards the latter part of his life, was most outspoken in … declaring that a disease was a living physical entity, an ens morbi:

"In my view the disease entity is an altered part of the body; in principle, an altered cell or cell aggregate … In this sense I am a thoroughgoing ontologist and have always regarded it as a merit to have brought into line with genuine scientific knowledge the old and essentially justified assertion that disease is a living entity … [which has] a parasitic relationship with the otherwise healthy body to which it belongs and at the expense of which it lives."' (Taylor, 1980)

As a result, it has now become customary, Taylor noted, to refer to a patient as having a gastric ulcer, having a mitral stenosis, having a pneumonia etc. Implicit in this kind of thinking is a dualism between a mind-based person and a body that simply conveys that person around. Whether this is a direct product of Cartesian dualism, I do not know, but I suspect that there is an innate human tendency to separate the experience of living from the body that does the living. To give a quite vivid example, just three weeks ago (5th Jan 2006) on the 6 O'clock News on Radio 4, of Ariel Sharon's suffering a stroke, it was stated that he was 'brought down by his body not by his enemies.' He and his body are spoken of here as if they were essentially separate things. But, the fact is that it is quite clear that none of us know of our personal existence without our having a material existence – certainly, none of us existed before we had bodies.

The effects of such dualist views are significant. Virchow's influence in reifying disease combined with our innate tendency to 'dualize' means that we have come to adopt a view of persons (or minds) possessing bodies which, in turn, have discrete disease entities situated within them. This is unfortunate because I suspect it obfuscates what could have been a more accurate picture – one I shall explore later on.

Another particularly unfortunate effect of Virchowian thinking has been to forget the etymology of the word 'disease': that it is literally dis–ease – 'a loose of ease'. Originally, it was not one of Virchow's physical entities belonging to the physical body alone but referred to an experience belonging to the personal part of the dualism. The starkest examples of this amnesia – or muddled thinking – are seen when the terms 'disease' and 'pathology' are used interchangeably. One of the biggest perpetrators of this has to be the BMJ where examples are not difficult to find. (This is probably the most obvious of which I am aware.)

Much that is written about disease and health uses the language of the reified entity when it should be addressing the organism that displays different states that we label 'dis-eased' and 'healthy'. Unfortunately, our understanding of organisms is not as good as we usually assume.

One approach we see very commonly in textbooks of anatomy and physiology these days is that of dividing the organism into different 'levels' of organization.

This approach certainly has its uses. Without doubt, it allows teaching to be broken down into coherent chunks. However, we now find that this approach is so commonly used that nobody, it seems, would dream of criticizing it. Unfortunately, the only person I know to have done so, only ever published in Italian. But, although the division of the organism into different levels of organization seems to have intuitive merit, questions remain. To give just one, why, in the three examples given here, does 'system' – or 'organ system' – appear when all the other divisions are distinctly structural? A system, in this context, is a construct – a way of trying to relate different parts with each other – and takes a fundamentally functionalist approach. Purely structuralist approaches, as adopted by Gray's Anatomy, generate quite different divisions.

Intellectually, these diagrams represent what might be called 'Reversed Reductionism' – or Reductionism Reversed. To sell, such texts must portray themselves as being about the health of whole individuals. The teaching is, however, fundamentally reductionist – which does not sit well with the prevailing ethos within many parts of the healthcare fraternity. Therefore, the arrows in these diagrams have been surreptitiously reversed to present the necessary guise.

The personal health emphasis followed by such texts means that Lakatos's suggestion – that 'to know the normal healthy body, [we must] study it when it is abnormal, when it is ill' – is given a low priority. These books are really about fostering health – not understanding human biology.

More importantly for today, however, it is necessary to point out that there is nothing in these textbooks about what whole organisms are or what it is to be one. The early chapters of such books describe the way the human organism is to be divided for didactic purposes, but having done so, there is never a concluding chapter that brings these divisions back together again to give any sense of how these parts constitute or produce an object that has distinct and peculiar properties. Occasionally, one might see a diagram such as this – which I have called 'constructionism' – but it doesn't really get us very far.

The question of understanding the organism is also conceptual. It is, perhaps, one of the large and difficult questions of biology but, for most biologists, it is not a very pressing one. In the textbooks that use this levels of organization approach, it seems to be assumed that we know what it is to be an organism since that is what each of us happens to be. If this is indeed the assumption, it is quite mistaken and it is important to spell this out. In terms of the dualism of which I spoke above, our primary experience is of our self. We know what it is like to be our self, not, I suggest, what it is to be an organism. The organism of which I speak is somatic. Although the nature of the latter obviously has a bearing on the former, our self and our soma are not identical. Significantly, this fact forms the basis for a common criticism of the prevailing model in western medicine: the so-called biomedical – or, sometimes, just medical – model. So far as I am aware, nobody ever deliberately proposed this model. It appears to represent a way of thinking that has emerged since the Enlightenment, rather than something deliberately contrived. That being the case, one cannot point to a single formulation but numerous, often passing, references. One of the most fundamental characteristics of the biomedical model, however, is that it holds that all illnesses and associated symptoms arise from some underlying condition or state of the body – in effect, from some anatomical or physiological lesion.

Illness, I should point out, has a clearly defined and technically acceptable definition – 'Illness … is a feeling, an experience of unhealth which is entirely personal, interior to the person of the patient.' (Marinker, 1975)

The biomedical model has proved to be unsatisfactory for a variety of reasons. It is clear, for example, that not all experiences of illness can be traced back to some underlying physical cause. Neither do all lesions give rise to symptoms of illness in the same way, or on all occasions. For some, the biomedical model has proved to be unpalatable simply because it adopts the reductionist approach – that we saw so carefully skirted around a few moments ago – and appears to reduce all personal experience to mere physical properties. Whatever one's views, it is clear that this model is in need of revision.

One alternative to the biomedical model is the 'Biopsychosocial model' proposed by the late George Engel. Engel's idea was not to replace the biomedical model, but to enhance it by prompting a careful analysis of the factors and events acting at different levels of organization within the organism and around it.

As suggested by its very name, this model seeks to combine bio–logical, psycho–logical and socio–logical perspectives pertinent to a patient's well-being, all at the same time. By so doing, Engel sought to take a more complete, whole-patient-as-a-person type approach.

The biopsychosocial model owes a debt to Ludwig von Bertalanffy's 'General Systems Theory' and has much in common with the levels approach to the organism mentioned above. However, although it continues to have its devotees – different groups of whom have recently produced a couple of significant volumes about its potential usefulness – it has, however, met with limited success. Despite initial optimism when first proposed in the late 1970s, it has failed to find the key role in somatic medicine that was intended.

There are various criticisms of this model but, without going into undue detail here, at least one hinges on our lack of a theory of the organism. In particular, there is a problem about how the prescribed levels really interact. As can be seen from these figures – which represent just two selected from a time series using myocardial infarction as an example – this model can accommodate a good deal of complex detail but its explanatory and predictive capabilities are quite limited.

Engel's model begs the question of whether it is necessary to have such detail to begin to understand disease and health and of whether to do so, we need to know what is going on at all these different levels. Instead of trying to answer these questions directly, I shall see what happens if we assume the answer to be: No. I feel justified in this approach because I am suggesting that the terms 'disease' and 'health' only properly apply to organisms per se.

To understand organisms in this way, most would assume it necessary to adopt some form of holistic approach. Such an approach emphasizes the interrelationship between the parts and the whole but that is not going to be my approach here – especially not since, for Engel, it proved problematic. It is possible to take the organism as an entirety in an atomistic way. Just as school chemistry taught that an atom is the smallest part into which an element can be subdivided before losing its distinct chemical properties, so one can think of the organism as that which cannot be subdivided without losing its own distinctive properties. What we need to do is select appropriate characteristics that describe the organism. I think, the lens of disease and health that I mentioned at the beginning, can help us do this.

Returning to the biomedical model, I noted that one of its fundamental features was that it holds that all illness arises from some underlying condition or state of the body. From this, we can infer two properties of organisms which are that they have a physical state that is variable and that there is some way of recognizing or monitoring this state so as to ensure survival. In humans, for example, this latter process manifests itself as the presence or absence of an experience of 'illness' which can be associated with a range of physiological and behavioural responses.

We could depict these properties graphically allocating physical state to the x-axis – because it appears to be an independent variable – and illness to the y-axis – because it appears to be a dependent variable. The most simplistic assumption of the biomedical model predicts that a linear relationship exists between the experience of illness and the physical state of the organism. Given this relationship, one would expect to be able to read off one in terms of the other: either the illness experienced in terms of the physical state of the organism or the physical state of the organism in terms of the illness being experienced.

Before pointing out the need to improve upon this formulation, it is worth noting that this graph prompts some interesting ideas. Although the biomedical model likes to predict a linear relationship between illness and physical state, the nature of that linear relationship is far from clear. Any number of lines with different gradients or shapes may be feasible depending on the constitution of the individual in question. Thus, there is scope for the notion of individual uniqueness to be accommodated and even portrayed within such a model.

Somebody we might describe as having a 'robust constitution' and another we might describe as having a 'frail constitution' might be represented thus:

However, a simple linear relationship between illness and physical state does not strictly apply. There can be situations where there are symptoms without signs and signs without symptoms and situations in between. Drawing things out in this two-dimensional format allows us to consider departures from the supposed line. So, instead of assuming that such lines are the only ways of linking physical state with illness, the idea of a space representing an individual's personal experience of their physical being is suggested. For this I shall use this as a representation. I have left an indication of a supposed linear relationship between physical state and illness just to give some feel for the constitution of the individual in question. Now, we may think of other associations of physical state and illness off of the line.

Also, since an individual's personal experience of their physical being is obviously finite, this representative space must also be limited and to represent this, two limiting boundaries are added to the axes such that the bounded space can be said to depict the entire existential experience that is open to a given individual.

But as I said, this current formulation needs improvement. As it currently stands, the x-axis represents progressively inferior states of the organism to go with worsening illness. The simple x-axis label 'physical state' is clearly inadequate. We could think of what this axis represents in terms of the entropy of the organism as a distinct system. So we could re-label this axis 'Organismal Entropy' so that this, as a measure of disorder, can increase as one moves along the x-axis in the positive direction. My fear is that putting the word 'entropy' in a new context may cause confusion given its other uses. I should note, however, that the idea of entropy applied to biological systems is not new. It occurs in Erwin Schrödinger's influential work 'What is Life?' – first published in 1944 – where he too talks about entropy in a biological context and goes so far as to refer to 'negative entropy' as the way in which organisms, in maintaining themselves, run contrary to the third law of thermodynamics. So we can talk of entropy in relation to organisms but for the time being, I am going to keep 'Physical State' but sub-title it 'Degradation' such that, as one moves along the x-axis in the positive direction, the general degradation of the physical state of the organism increases. It is important to note that by 'physical state' I am referring to one unified, and therefore hypothetical, descriptor of the organism as an entirety.

Perhaps more problematic is the fact that currently, this diagram uses an increasing scale of illness – as one moves up the y-axis, the measure of illness increases. That being the case, we have no real baseline against which to operate.

I noted above that organisms have ways of recognizing or monitoring their variable physical states and that in humans this process can manifest itself as the presence or absence of an experience of 'illness'. Illness is only part of a wider reflexive process. So instead of 'illness', I intend re-labelling this axis 'Reflexive State' as an indication of all the ways in which the physical states of the organism are referred back and made known to itself consciously and unconsciously. Thus, these two axes represent physical and informational aspects of the organism.

If we then flip the y-axis, we can have, as our baseline, the cessation of this reflexivity: the point where – at a y value of zero – organismal death is represented. To be clear, this is organismal death, the death of the organism as an entity in its own right. It is not synonymous with the serial or parallel death of its component organs and tissues. This, I think, is a conceptually satisfactory baseline because above it the organism can be said to exist as an organism per se.

As given, this represents a diagram or model for one individual. All can be said to share the same 'baseline' but no two individuals can be expected to share the same diagram. No two people will share the same bounded space which, after all, represents the entire existential experience that is open to an individual. No two people have the same existence as they are materially and constitutionally different

This is perhaps a good time to return to the list I showed earlier when I asked you to say which was a disease and why. This list comes from a study reported in the BMJ in 2002. Four groups were asked to say whether they thought each of the conditions on the list was a disease or not. The percentage of those in each group who thought a given named condition was a disease is indicated

Although opinion converges towards the top, we notice that there are differences of opinion within groups and between groups throughout. Clearly, deciding whether something merits being called a disease is not an easy proposition. However using the diagram I have just outlined we can now take a different approach entirely: we can now look to the organism. Instead of trying to say what disease or health are – by trying to characterize their essential features – and instead of trying to say whether a given condition is or is not a disease – from what we know of their signs and symptoms – we can try to map a subject's state onto this diagram. We cannot do this numerically – this is, after all, a conceptual approach – but we can make informative distinctions. For example, if we were to ask people whether they thought cancer in general was a disease, the majority, I think we can agree, would said: 'Yes'. In fact, they might even preface their answer with 'What a silly question' – hence, my choice of this example. The philosopher Georges Canguilhem posed an enduring puzzle. A man is walking along the road one day when he is attacked and murdered. Upon autopsy, he is found to have cancerous lesions about which nobody – not even the dead man – had previously been aware. Did that man have a disease?

The man had lesions – that is not at issue. He may have benefited from medical attention to prevent later problems had he lived – that is not at issue. The question is whether we can say that somebody has a disease – or is diseased – based upon the presence of lesions alone. Clearly, an organism's response to a lesion cannot be predicted from a knowledge of the lesion alone. Much depends upon the nature of the organism and how it responds to what lies within. In a real sense, rather than simply asking whether something is or is not a disease, we should, I think, look to the organism to tell us what it makes of the situation.

Using the diagram I have just outlined, we might map the condition of Canguilhem's murder victim, thus:

The overall measure of his physical state may be assumed to be shifted somewhat to the right but, noticeably, his 'reflexive state' is not significantly diminished. His body is able to accommodate the lesions without obvious signs of distress. Significantly, up until the point of his death, his ability to continue to exist – to survive - as an organism was not appreciably impaired. To put it another way, 'Whatever it is that organisms are supposed to do, he was able to do it.' So, whatever the clinical view, the biological view has to be that, as an organism, he was 'successful'. Thus, we are able to point to a fundamental conceptual difference between clinical and biological understanding of disease and health.

One theory of health that I have chosen not to go into today – called the Bio-Statistical Theory – holds that disease can be considered from a statistical point of view as 'statistically species-subnormal biological functioning'. Because of the way it has been formulated, it tends to be favoured by those from a more scientific background. However, I choose to close with mention of it because it has prompted an interesting remark from the philosopher William Stempsey (2000) who suggested that for the bio-statistical theory to survive 'it must live by the considered usage of someone other than pathologists'. The major task of pathologists, he thought, was 'to find morphological correlates and biological explanations of phenomena that clinicians and patients call disease.' Someone better was needed and, Stempsey suggests, biologists 'would be the most likely candidates.' In saying this, he implies something very subtle. If the role of pathologists is 'to find morphological correlates and biological explanations of [various] phenomena' then there must be something extra that biologists should be able to bring to the party. However, so far as I can see, most biologists interested in disease do little more than what Stempsey saw pathologists as doing – that is, focusing on lesions. In so doing, what inevitably follows is a continued Virchowian confusion of lesion with disease.

However, in suggesting a role for biologists – or at least the more enlightened ones – Stempsey suggests that this 'has the implausible consequence of holding that disease is best understood by people who are not physicians' (Stempsey, 2000). I do not find this in the least bit implausible. In fact, I would argue quite the opposite; it is biologists, I believe, who are potentially best situated to deal with the issue. Biologists can deal with organisms instead of persons; therefore they should be able to take a less value–laden and more dispassionate view of the conceptual biological basis of the human physical condition. They should also be able to take a wider – less anthropocentric – view in that there are organisms other than humans to which the terms disease and health are often applied and that these too have to bear the consequences of their own existence in their own way. Furthermore, if the notions of reflexivity and physical degradation (or entropy) that I have outlined here do apply to organisms – and I am confident they do (although work remains to be done in testing the idea) – then the consequences of these should be describable in fundamentally biological – that is, evolutionary – terms. For this, the biologist is certainly best equipped.

Acknowledgements:

I would like to thank the trustees and fellows of the Konraad Lorenze 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.