Healthcare theory
Last updated: October 17, 2025
What theory underlies the delivery of healthcare? The design of hospitals, services, policies, and almost every other aspect of healthcare in the UK occurs without reference to any theories. Yet, as Priscilla Alderson stressed in 1998, theories are crucial: “… theories are at the heart of practice, planning, and research. All thinking involves theories …” She emphasised that all planning involved theories, whether acknowledged or not, saying, “… when theories are implicit, their power to clarify or to confuse, and to reveal or obscure new insights, can work unnoticed.” In this post, I examine the implicit theory underlying healthcare, considering whether it is suitable for rehabilitation services in contrast to acute services, and why a new theory is necessary for rehabilitation.
If you think theories are an unnecessary luxury, consider how you approach a breakdown in your car, a problem with your computer and printer, or a discussion about the best way to set goals. In each case, you will use an implicit theory about how the car, computer, or setting of goals achieves its purpose. Your response might be better if you made your theory explicit in each case.
Table of Contents
Introduction
Humans solve problems. Initially, this likely involved random trials to see what happened; we may still do the same if faced with a new situation. Early philosophers in Ancient Egypt, Greece, and Persia soon developed more systematic methods of investigation. These involved understanding the phenomenon and identifying similarities to problems that had already been solved.
Over time, a more systematic approach developed, collecting sufficient data to determine the type of problem for further analysis. One way to characterise a type is to ask, What model is appropriate for this problem? For example, is it a logical puzzle, a linguistic problem, a mechanical issue, a behavioural problem, etc.?
Ill health is a common problem, and people with expertise in helping people with ill health emerged in most cultures; some were priests, others wise people, etc. Their common feature was that they depended on an explanatory model when deciding what to do.
For example, if the explanatory model concerned offences against gods, some action to appease the gods would be recommended. Homeopathy is another example of an explanatory model, its key features being:
- A substance that produces similar symptoms in healthy people will cure the problem.
- The lower the dose of the treatment, the greater its effectiveness.
Using these principles, a treatment is recommended.
Considering current healthcare, I distinguish two components. Individuals use their personal explanatory model to manage illness; they have a private healthcare theory. Simultaneously, any socially supported system adopts a widely accepted model, which forms the basis of public healthcare theory. I am examining public explanatory models.
Emergence of a public model.
The primary public model of illness is the biomedical model, which I have described. I will recapitulate its evolution here.
Throughout most of history, people and societies have employed various explanatory models to understand illness. One example is the model based on the balance of four humours, which Hippocrates may have developed from Empedocles’s theory about the elements of matter. It influenced healthcare for centuries. It differed significantly from most earlier models by attributing illness to a natural phenomenon rather than a mystical or spiritual cause. Another influential model is the Yin-Yang theory of balance, which forms the basis for Traditional Chinese Medicine.
Until the end of the fifteenth century, the theories were not supported by evidence; they were eminence-based, not evidence-based. With the gradual development of the scientific method, starting with the idea of discovery, models began to be based on evidence about the relationships between events or different factors. Consequently, investigators began to identify the causes and consequences of specific diseases.
In the mid-nineteenth century, the method for identifying the specific agent responsible for an infectious disease became well-established – Koch’s postulates. These are still used, although modified and improved, to incorporate new knowledge, as described, for example, in a paper by David Fredricks and David Relman.
Over about 150-200 years, many syndromes (i.e., a collection of similar symptoms, signs and other phenomena) were disaggregated into specific disorders with a known cause and natural history. Though new disorders continue to be identified, most progress now concerns refining diagnoses or identifying subdivisions within a disease, such as grading malignant tumours.
As progress was made, the public explanatory model became refined and simplified and was increasingly recognised within healthcare and by the public. It was never named, described, or even identified as a model, as it slowly emerged without any sudden change. Furthermore, change continued, albeit at a slower rate, after 1950.
The healthcare theory and model.
By about 1950, the scientific and public explanatory model for understanding sickness was well-established and widely used. It is now called the medical model; a better name is the biomedical model of illness.
Although not stated, this model is the intellectual basis for many aspects of the UK National Health Service. However, the model is not a theory that expounds on the provision and purpose of healthcare services. It is a strong foundation on which a healthcare theory can be built.
The biomedical model of health has two fundamental axioms:
- All symptoms are caused by a disease:
- Symptoms mean any change or alteration in bodily functioning (activities) or experiences (sensation, etc.)
- Disease means an obervable structural or functional abnormality of or in the body (pathology)
- Symptoms will only arise in the presence of disease. (i.e. they are symptomatic).
- e. Disease always underlies symptoms; there can be no other explanation.
Although not intrinsic to the model, other clinical assumptions are inextricably associated with the model:
- Bodily experiences and functions are separate from and unrelated to the mind
- The nature of the mind is unclear, but it encompasses emotions, beliefs, attitudes, and experiences, such as auditory hallucinations, with no apparent bodily explanation.
- All symptoms that a person with a diagnosed disease experiences are attributed to that disease.
- Patients only have one disease that explains a set of symptoms
- The model assumes that only one disease is pre-eminent
- The model is challenged by multi-morbidity
- Cure or control of the disease will abolish, or at least reduce, all symptoms.
Last, there are some associated cultural assumptions, first described by Talcott Parsons in 1951 in ‘The Social System’, which introduced the concept of the sick role:
- The sick person has two rights:
- To be temporarily exempt from their usual social roles, such as working or looking after the house. The exemption is proportionate to the severity of the sickness.
- They are not to be blamed or held responsible for their sickness and will consequently be supported by others until they recover.
- The sick person has two obligations. They must:
- Consider the sick role undesirable and get well as quickly as possible.
- Seek expert healthcare help and cooperate fully with any treatment or advice offered.
The biomedical model underpins all healthcare services, even though, for instance, mental health issues are not included within it. Nevertheless, the design, management, and funding of mental health services share similar assumptions; all mental health symptoms are attributed to a single ‘diagnosis’ (assumed abnormality of mental function), and every symptom signifies an underlying ‘diagnosis’.
The resultant biomedical healthcare theory is that a person’s symptoms should be investigated until the underlying, causal disease has been established, when a disease-modifying treatment or advice should be given to achieve the best control or cure possible.
To the best of my knowledge, no one has explicitly stated the theoretical underpinning of the healthcare model that is used almost universally.
Difficulties in biomedical healthcare.
The theory has yet to be made explicit because everyone grew up with the biomedical model and just accepted the healthcare system based on it. As Priscilla Alderson stressed in 1998, “when theories are implicit, their power to clarify or to confuse, and to reveal or obscure new insights, can work unnoticed,” and, precisely as she said, difficulties arise which are not recognised as arising from a faulty theory. Peter Halligan and I drew attention to this 20 years ago, but despite 899 citations (Google Scholar, October 2025), it has not altered practice!
Before considering the weaknesses in the theory, it is essential to acknowledge its successes. When a previously healthy person becomes sick and visits a doctor, healthcare based on this theory is often effective. The theory has:
- Identified a huge number of specific disorders, often also establishing specific treatments; the size of the International Classification of Diseases (WHO ICD) illustrates this.
- Stimulated advances across a range of specialities such as genetics, pharmacology, and surgery.
- Justified effective public health measures such as vaccination, provision of clean water and effective sewage systems, and, to a limited extent, avoidance of harm from alcohol, smoking, and other lifestyles.
- Benefited many millions of people.
Still, its success rate is declining, and its weaknesses are becoming more troublesome. Some examples are:
Over-investigation.
The expectation of a single disease diagnosis encourages and almost enforces over-investigation. This may cause harm, increase patient concern, and cause anger or other emotions when no disease is found. At the same time, it prevents considering alternative explanations such as a functional disorder, anxiety or depression, or a ‘normal’ experience with no association with disease. It may delay or even prevent appropriate treatment.
The absence of a disease challenges healthcare.
Any patient with a definite illness who presents with health-related problems and attends healthcare services but where no disease is often stigmatised, disbelieved, or treated with less sympathy. Healthcare staff and services cannot manage such patients because they cannot be categorised, there is no specific curative treatment, and no ‘test’ will make a definite diagnosis. On the other hand, this situation is frequent; 20%-25% of all outpatients and maybe 5% of inpatients fall into this group. Potentially effective therapy may not be given.
Treatment failure also challenges healthcare.
The expectation that a treatment will cure the disease and remove symptoms is often unmet for many reasons, such as the disease found was unrelated to the symptoms arising from other factors or the symptoms have become embedded in some way (e.g. nocioplastic pain). The resultant risk is that increasing despair leads to the trial of many treatments, often combined, causing considerable iatrogenic harm.
Disease treatment is equated to the ending of healthcare responsibility.
The patient has significant continuing symptoms after the cure, which is only partial. Yet, the healthcare service states there is no further responsibility on them as they have found and treated the disease. The patient does not appreciate being told they should leave the hospital if they are, for example, significantly disabled. The whole problem of ‘delayed discharge’ arises from this theory interpretation. I have discussed this issue concerning the Reason to Reside criteria and being ready for discharge.
Disease diagnosis data are often misused.
All healthcare data collected and used is centred on the disease diagnosis, yet most diseases have a spectrum of severity from minor to severe. Stroke, for example, covers everything from two days of weakness in the arm to a lifetime of a prolonged disorder of consciousness after a subarachnoid haemorrhage. Basing reimbursement on diagnosis on disease diagnosis is unfair because most of the cost arises from associated disability and dependence.
Failure to collect appropriate data.
The lack of routine data on disability hinders service planning and delivery. There are no data on the number of people discharged from the hospital with incontinence, limited mobility, significantly reduced communication ability, and a need for assistance with dressing or cooking, yet all these factors are critical when planning community services.
It limits perspective
This theory’s most pervasive and insidious consequence is its effect on broader public policy and resource allocation. It fosters an attitude that society (the State) has fulfilled all its duties of care for sick people.
Society now pays little attention to the broader causes of disease and sickness, nor is it concerned with the wider consequences, as it focuses on the individual and their specific illness. Responsibility for everything else is shifted to the person. A person’s obesity is entirely blamed on them, not poverty secondary to inadequate wages and social security, not the low quality of the food they can afford, not the easy and cheap availability of alcohol, not the appalling housing available, not the polluted atmosphere, etc.
This unspoken but widely accepted view needs to recognise the significant influence of social factors that directly and causally increase the risk of ill health. It also neglects the importance of supporting the individual’s adaptation to their new circumstances or maximising their return to their previous activities and social roles. These are vital healthcare responsibilities, but the excessive emphasis on autonomy and freedom to make unwise choices, coupled with a failure to acknowledge the influence of the social environment, leads to the conclusion that society has no responsibility for a person’s well-being.
Thus, as predicted, the implicit theory of healthcare services causes harm, and one particularly significant area of harm is the devaluation of rehabilitation; we are not entirely overlooked, but we are only given a small proportion of the attention and resources needed.
Conclusion
One solution is to develop a comprehensive General Theory of Rehabilitation that challenges the implicit general theory of healthcare, which focuses solely on the diagnosis and treatment of disease. This now exists, but it is unlikely to influence policymakers.
A better approach is to shift the culturally dominant theory underlying healthcare from the biomedical model to the holistic biopsychosocial model, as the biomedical model is also unsuitable for other services, including mental health and psychiatric services, services for people with learning disabilities, services for older adults, and palliative care services. The long-term solution is to develop a biopsychosocial theory of healthcare that covers the entire spectrum of health, not just disease. This would be a holistic, person-centred healthcare theory, and I have published an initial proposal here.