Philosophy of Medicine

An Introduction

R. Paul Thompson, Ross Upshur

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351660747
• Edition: 1
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

What kind of knowledge is medical knowledge? Can medicine be explained scientifically? Is disease a scientific concept, or do explanations of disease depend on values? What is "evidence-based" medicine? Are advances in neuroscience bringing us closer to a scientific understanding of the mind?

The nature of medicine raises fundamental questions about explanation, causation, knowledge and ontology – questions that are central to philosophy as well as medicine. This book introduces the fundamental issues in philosophy of medicine for those coming to the subject for the first time, including:

• understanding the physician–patient relationship: the phenomenology of the medical encounter.

• Models and theories in biology and medicine: what role do theories play in medicine? Are they similar to scientific theories?

• Randomised controlled trials: can scientific experiments be replicated in clinical medicine? What are the philosophical criticisms levelled at RCTs?

• The concept of evidence in medical research: what do we mean by "evidence-based medicine"? Should all medicine be based on evidence?

• Causation in medicine.

• What do advances in neuroscience reveal about the relationship between mind and body?

• Defining health and disease: are explanations of disease objective or do they depend on values?

• Evolutionary medicine: what is the role of evolutionary biology in understanding medicine? Is it relevant?

Extensive use of empirical examples and case studies are included throughout, including debates about smoking and cancer, the use of placebos in randomised controlled trials, controversies about PSA testing and research into the causes of HIV. This is an indispensable introduction to those teaching philosophy of medicine and philosophy of science.

1 Philosophy of medicine

Its scope and subject matter

Three domains of philosophy are principally embraced by philosophy of science: epistemology (i.e. how knowledge is acquired and what it is to “know” something), metaphysics (i.e. the role and nature of cause and effect, and space and time) and logic (i.e. the nature of scientific reasoning and the logical structure of models and theories). The examination of some aspects of science draws on more than one of these domains; examining the role of models and theories, for example, involves exploring their logical structure as well as their role in knowledge acquisition and expression. Philosophy of medicine, like philosophy of biology and philosophy of physics, is a branch of philosophy of science and, hence, also embraces these three domains of philosophy.

The fourth domain of analytic philosophy is ethics. During the last 50 years or so, increasing attention has been paid to ethical issues in medicine with an attendant increase in articles and books on ethical aspects of medicine. This enterprise is known as bioethics. Opinions differ about whether bioethics is a full-fledged discipline or a sub-discipline of ethics. Its practitioners include lawyers, theologians, sociologists, physicians, philosophers and others. Given the array of backgrounds of its practitioners, the lack of a common set of requirements and no common methodology, we suggest that it is not a discipline.

Whatever the resolution of that issue, in this book, we treat philosophy of medicine as a branch of philosophy of science. Consequently, ethics does not play a large role. There are occasions, however, where it does have tangential relevance; values may be influencing research methodology or medical knowledge may have obvious ethical implications. Fortunately, there are a large number of books and articles on these matters; hence, we need not digress from the central foci of philosophy of science. Where appropriate, we refer readers to the existing literature.

This description of the philosophical domains involved in philosophy of medicine is somewhat abstract. Examining two historically important medical events will illustrate the nature of a philosophical analysis of medicine in a more concrete way and will more sharply characterise the matters with which philosophy of medicine is concerned.

In 1753, James Lind, a Scottish physician, described his experiment on the treatment and prevention of scurvy. Today, scurvy is known to result from a deficiency of vitamin C (ascorbic acid); the name ascorbic derives from the Latin name for scurvy, i.e., scorbutus. It is a debilitating and ultimately fatal disease if not treated. In Lind’s time, it was the scourge of seamen on long voyages. The symptoms include inflamed and bleeding gums, bleeding into the skin, joints and body cavities, weakness and fatigue.

Lind described his experiment in his (1753) A Treatise of the Scurvy. In Three Parts. Containing An inquiry into the Nature, Cau∫es, and Cure, of that Di∫ea∫e (the “∫” today is rendered “s”). The relevant passage, in more modern English, with italics as in the original, is:

On the 20th May, 1747, I took twelve patients in the scurvy on board the Salisbury at sea. Their cases were as similar as I could have them. They all in general had putrid gums, the spots and lassitude, with weakness of their knees. They lay together in one place, being a proper apartment for the sick in the fore-hold; and had one diet in common to all, viz., water-gruel sweetened with sugar in the morning; fresh mutton-broth often times for dinner; at other times puddings, boiled biscuit with sugar, etc.; and for supper barley, raisins, rice and currants, sago and wine, or the like. Two of these were ordered each a quart of cyder a day. Two others took twenty-five gutts of elixir vitriol three times a day upon an empty stomach, using a gargle strongly acidulated with it for their mouths. Two others took two spoonfuls of vinegar three times a day upon an empty stomach, having their gruels and their other food well acidulated with it, as also the gargle for the mouth. Two of the worst patients, with the tendons in the ham rigid (a symptom none the rest had) were put under a course of sea-water. Of this they drank half a pint every day and sometimes more or less as it operated by way of gentle physic. Two others had each two oranges and one lemon given them every day. These they eat with greediness at different times upon an empty stomach. They continued but six days under this course, having consumed the quantity that could be spared. The two remaining patients took the bigness of a nutmeg three times a day of an electuray recommended by an hospital surgeon made of garlic, mustard-seed, rad. raphan. balsam of Peru and gum myrrh, using for common drink barley water well acidulated with tamarinds, by a decoction of which, with the addition of cremor tartar, they were gently purged three or four times during the course. The consequence was that the most sudden and visible good effects were perceived from the use of the oranges and lemons; one of those who had taken them being at the end of six days fit for duty. The spots were not indeed at that time quite off his body, nor his gums sound; but without any other medicine than a gargarism or elixir vitriol he became quite healthy before we came into Plymouth, which was on the 16th of June. The other was the best recovered of any in his condition, and being now deemed pretty well was appointed nurse to the rest of the sick.

(pp. 192–193)

Lind’s experiment has a sample of 12 scurvy sufferers. He was satisfied that their cases were sufficiently similar that any outcome of his interventions would not be due to differences in the severity, duration and so on of the disease. He also attempted to ensure that the physical environment was the same for all and the general diet was the same for all. The only thing that varied was an addition to their diet. He created six groups of two people. Each group had a different dietary supplement. His, now famous, result was that the group whose diet was supplemented with two oranges and one lemon improved quickly and dramatically.

The obvious immediate question is, was he just lucky? Twelve is not a large sample size; two individuals per group is very low; assessing the similarity of disease conditions was a subjective judgement by one person. Moreover, the choice of two oranges and one lemon for one group seems fortuitous. Why did he try that supplement and why in those quantities? These questions probe the adequacy of his experimental design, his methodology and his conclusions. Assessing the adequacy of these falls within the scope of philosophy of medicine. Other issues need probing as well. Does the experimental result justify any claims about causes of scurvy or the efficacy of this “cure”; if it does, then what kind of causal claims are they? The experiment seems to provide some “evidence” of a link between citrus fruits and amelioration of the symptoms of scurvy. What kind of “evidence” is it and how adequate is it for drawing conclusions regarding treatment? Surely, dose and timing of the treatment will matter. If so, what further work is needed to reveal the answers? Would subsequent treatment of those with symptoms of scurvy be important? Would similar remarkable recoveries strengthen the belief that this is an effective treatment? Given that differential diagnosis (distinguishing diseases based on symptoms) is complicated, and more so in the eighteenth century, some people with symptoms of scurvy may have some other ailment. That they will likely fail to respond to the therapy is not surprising but how should the data be interpreted? Examining these matters also falls within the domain of philosophy of medicine.

Then there are some larger matters that arise from Lind’s discovery that fall within the scope of philosophy of medicine. Can his discovery – the link between citrus fruit and recovery from scurvy – be integrated with other knowledge in medicine at the time? Does it need to be? Can a model be developed that quantitatively describes features of the relationship Lind uncovered; for example, the relationship of the quantity of citrus fruit ingested and the speed of recovery? Are such models useful? Given the importance of models in modern science, it would be surprising if a model, even a simple model, were not to be important here. To underscore this point, consider a twentieth-century example, one that one of us has used before (Thompson 2011a): Bolie’s model (1960) of the relationship of glucose and insulin. The model is important in the understanding and management of diabetes.

The principal role of insulin is to mediate the uptake of glucose into cells. A deficiency of, or a decreased sensitivity of cells to, insulin results in an imbalance of glucose uptake, resulting in severe physiological problems, which if untreated lead to kidney, eye and nervous system deterioration and ultimately to death. In some cases, treatment can be based on a dietary regime; in others, daily doses of insulin are required. Insulin is a protein. The sequence of DNA that codes for the production of the human insulin protein has been mapped and constructed. This DNA segment is inserted into a region of a plasmid in a bacterium; the bacterium then becomes a bio-factory for the production of insulin. Today, virtually all insulin used in rich countries is produced by genetically modified bacteria. Understanding the dynamics of the regulatory system allows considerable refinement to a therapeutic regime of insulin.

Bolie’s model is very simple; it assumes only three entities (glucose, insulin and extracellular fluid) and identifies nine variables:

Extracellular fluid volume	V
Rate of insulin injection	I
Rate of glucose injection	G
Extracellular insulin concentration	X(t)
Extracellular glucose concentration	Y(t)
Rate of degradation of insulin	F1 (X)
Rate of production of insulin	F2 (Y)
Rate of liver accumulation of glucose	F3 (X, Y)
Rate of tissue utilisation of glucose	F4 (X, Y)

F ₁ (X, Y) through F₄ (X, Y) are functions of X and Y at specific times. Bolie’s dynamical system has equations:

Insulin: dX/dt = (I – F₁(X) + F₂(Y))/V [the expression dX/dt = the change in X with respect to change in time – change in X per unit time]

That is, the change in extracellular insulin concentration with respect to time equals the rate of insulin injection minus the natural rate of its production minus the rate of its degradation, all divided by the volume of extracellular fluid. The division by the volume of extracellular fluid means the change in insulin is expressed as a change per unit volume of extracellular fluid.

Glucose: (dY/dt) = (G – F₃(X, Y) – F₄(X, Y))/V

That is, the change in extracellular glucose concentration with respect to time equals the rate of glucose injection or ingestion minus the rate of liver accumulation of glucose minus the rate of tissue utilisation of glucose, all divided by the volume of extracellular fluid.

Lind’s discovery of the connection between citrus fruits and the prevention of scurvy would have been enhanced if a mechanistic account such as Bolie provides for the dynamics of insulin were known. Today, of course, we know the effective agent, L-ascorbic acid (aka vitamin C), and its function and the dynamics of its action. Although this knowledge confers significant benefits with respect to the prevention and treatment of scurvy, Lind’s works demonstrates that simple experiments can yield successful medical interventions.

Turning to a different event in the history of medicine – the discovery of a smallpox vaccine – provides an additional illustration of the foregoing philosophical matters arising in medicine and also draws out others. Smallpox (variola) inflicted misery and death on hundreds of millions of people; those who survived the horrors of the symptoms were left disfigured and often disabled, with loss of vision for example. Jennifer Lee Carrell in her historical fiction, The Speckled Monster: A Historical Tale of Battling Smallpox (2004), captures this eloquently:

For all our current fears, we are inestimably lucky to live in a world in which the threat of smallpox has shifted from ordinary to extraordinary. Paradoxically, in the absence of smallpox as an everyday enemy, it is hard to realise just how lucky we are. Sheer numbers may help. By the time the disease was vanquished in 1977, it had become far and away the most voracious killer ever to stalk the human species. With a victim count in the hundreds of millions, smallpox killed more people than the Black Death and all the bloody wars of the twentieth century put together.

(p. xiv)

Jared Diamond in, Guns, Germs, and Steel (1999), holds that smallpox arrived in Rome around 165, presumably from Asia, so it is also a very old disease:

Another bonanza [for microbes] was the development of world trade routes, which by Roman times effectively joined Europe, Asia, and North Africa into one giant breeding ground for microbes. That’s when smallpox finally reached Rome, as the Plague of Antoninus, which killed millions of Roman citizens between A.D. 165 and 180.

(p. 205)

In 1980 the World Health Organization declared smallpox eradicated, although the report of the last case was sent to it two years earlier from Nairobi, Kenya. The road to eradication was long and began at some point in the 1600s in lands to the east of the Mediterranean Sea known as the Levant.¹

The first western reports of a practice in the Levant of inoculating people with pus from the pustules of those with smallpox appeared in the Philosophical Transactions of the Royal Society in 1714. In two separate communications that year Emanuel Timoni and Jacob Pylarinius reported on the practice and its successes. Timoni’s letter was reported by John Woodward who conveyed in English the main points of the letter (published in Philosophical Transactions; see Timoni and Woodward 1714):

V. An Account, or History, of the Procuring the SMALL POX by Incision, or Inoculation; as it Has for Some Time been practised at Constantinople

Being the Extract of a Lett...

Table of contents

• Cover
• Title
• Copyright
• Dedication
• Contents
• List of Illustrations
• Preface
• Introduction
• 1 Philosophy of medicine: Its scope and subject matter
• 2 Defining health and disease
• 3 Theories and models in medicine
• 4 Materialism and reductionism in science and medicine
• 5 Probability and randomness
• 6 Causality and induction
• 7 Randomised controlled trials, other study designs and meta-studies
• 8 Some central measures in clinical medicine
• 9 Reasoning in clinical practice: Prevention, diagnosis, therapy, prognosis, rehabilitation and palliation
• 10 Medicine from first-person perspectives: Phenomenology, narrative of knowledge and qualitative approaches to knowledge creation and use in medicine
• 11 Neurosciences and diseases of the mind
• 12 The varieties of modern medicine: Evolutionary medicine, evidence-based medicine, precision and personalised medicine and alternative medicine
• Bibliography
• Index