The clinical limits of Occam's razor

During the 20th century, remarkable developments in epidemiology and public health, combined with advances in knowledge about human physiology and pathology, resulted in major improvements in health and longevity, at least in rich countries. The development of vaccines and antibiotics led to the control of many infectious diseases. The emergence of sophisticated diagnostic technology, together with advances in surgery and the production of an increasingly powerful armamentarium of effective drugs, ensured that something could be done for the control, if not the prevention, of at least some common diseases.

The Cartesian view of illness as a breakdown of the body's machinery that lay behind these advances has had its downsides, however. As medical practice became increasingly technological, doctors were perceived to have lost their former skills of communication and many other aspects of good pastoral care. Increasing criticism of the profession along these lines has led to soul searching and endless reorganisation of the pattern of medical practice and education.

Another problem emerged after the Second World War. The virtual disappearance of communicable disease as a major killer in developed countries suggested that, if medicine could perform this miracle, the control of non-infectious diseases would follow; premature death would be a thing of the past and everybody would have the right to good health and longevity. Unfortunately, the diseases that replaced infectious disorders proved more intractable, and progress towards the control of disorders such as heart disease and cancer was much slower. For many common conditions - including "functional" disorders that repeatedly took patients to their GPs but had no apparent rational basis - little could be done. Because conventional medicine seemed to be failing, there was an increasing tendency to seek out those who offered hope and symptomatic treatment.

The growth in alternative, or complementary, medicine has been staggering.

A survey in the US in 1990 showed that patients made more than 425 million visits to unconventional therapists, compared with 388 million to primary care physicians. By the mid-1990s, there were 30,000 practitioners of complementary medicine in Britain. However, the divide between orthodox medicine and rival systems remains almost as wide today as it was in 1518, when the Royal College of Physicians gave its president the power to fine unorthodox healers. Hence, the almost simultaneous appearance of two books dealing with these diverse approaches to medical practice offers an opportunity to determine whether they will ever come closer together for the benefit of patient care.

Michael Sargent offers an extremely thorough account of the scientific background to improvements in healthcare that followed achievements in clinical research and drug discovery in the 20th century. He rounds off the story with a discussion of recent medical developments following the Human Genome Project and the hopes for advances in clinical care raised by stem-cell biology. Although he sometimes underplays the complexity and timescale of the evolution of the clinical fallout from the genome project, this is one of the best accounts of the development of scientific medicine that is available for the general reader.

Toby Murcott's story of the rise of alternative medicine, although much shorter, is equally valuable. Beginning with an account of a few of the numerous alternative therapies currently available, he goes on to point out that there is not a shred of scientific evidence about how any of them might work or whether they are genuinely effective. He goes on to describe the rediscovery of evidence-based medicine, first developed in the mid-19th century through the work of Pierre Charles Alexandre Louis in Paris, or possibly earlier, and its holy grail, the controlled clinical trial.

Discussing the problems of clinical trials for both conventional and unconventional medicine, he underlines the extreme difficulties of using this approach in trials of alternative remedies.

Murcott rounds off his story with a description of several clinical trials that are evolving in the field of alternative therapy, which bring together expertise in design from a wide range of fields including conventional medicine. Although it will be some time before the results of these studies are available, he ends on a note of optimism, suggesting that the two faces of medicine are at last attempting to come together with a common objective. This is by far the most balanced account of this field and should be read by every doctor and clinical scientist, as well as the general audience to whom it is addressed.

The juxtaposition of the messages from these two excellent books offers food for thought about the evolution of medical research and practice. As conventional medical science continues to reduce the frequency of premature deaths, the problems still to be faced reflect the complex multiple pathology of ageing. It may be a long time before conventional medicine gets to grips with the causes of many disorders of old age, if it ever does. And it has yet to make a start in trying to understand the pathological basis for the many ill-defined chronic ailments that fill our GPs' surgeries. But at least it has increasingly powerful tools to tackle these problems.

The physiological basis for some of the apparent successes of alternative medicine is also becoming amenable to modern research technology.

Neuroscientists have recently provided some fascinating evidence about the physical basis for the placebo effect, for example. Hence, while much of the value of alternative practitioners' work reflects the time they spend talking to their patients, there may well be more to it than this - a possibility that is starting to be explored by behavioural sciences.

When historians look back on the beginning of the 21st century, they may well conclude that this was the moment when the biological and medical sciences finally began to appreciate the multi-layered complexity of all living things, and of sick people in particular. As Francis Crick put it:

"While Occam's razor is a useful tool in the physical sciences, it can be a very dangerous implement in biology. It is thus very rash to use simplicity and elegance as a guide in biological research." If nothing else, this realisation should breed a more healthy level of humility, lacking for so long in those who practice biological and medical research and in those who apply its fruits to the care of sick people.

Sir David Weatherall is emeritus regius professor of medicine, Oxford University, and chancellor, Keele University.