For 5,000 years, doctors healed nothing. Now they can cure almost everything except the soul, argues Amanda Foreman
The Greatest Benefit to Mankind: a medical history of humanity

by Roy Porter

HarperCollins, pounds 24.99

Epidemics and History: disease, power and imperialism

by Sheldon Watts

Yale University Press, pounds 29.95

When the Scottish quack James Graham set up his fertility clinic in London in the 1780s, thousands of women queued to buy his special elixir. He also offered in-house treatment. For 25 guineas, a childless couple could pass the night making love on his celestial bed while music and so-called electromagnetic energy were piped in from an adjoining room. The scheme made Graham rich and, despite the absurdity of his methods, few questioned his claims.

It is tempting to think that the 20th century is free from such nonsense - that science has triumphed and the medical profession, not to mention Western society, has rid itself of superstition and irrationality. But one only has to read the "alternative medicine" advertisements in US health magazines to know this is not true. In New York's Free Spirit magazine, the sick can choose from practitioners who include crystal therapists, holistic dentists and Robert W Johnson, DD PhD, a "celebrated" spiritual counsellor who has made contact with the angels from Alpha Centauri.

The paradox of Western medicine, as Roy Porter points out in his intelligent and highly readable The Greatest Benefit to Mankind, is that bio-medical science can categorise, prolong and clone life, but does not hold the answer to its "deeper" meanings. According to Oliver James, among others, science and capitalism are largely responsible for the Western syndrome of "doing better, feeling worse". That is why Hollywood stars and Seattle housewives are turning in droves to television personality Dr Deepak Chopra. His concoction of cyber-babble and Eastern spiritualism provides the comfort millions find lacking from prescriptions for anti-fungal cream. "Your body is... miraculous," Chopra says in Ageless Body, Timeless Mind. "Every cell is a miniature terminal connected to the cosmic computer."

The confusion over medicine's purpose convinced Porter of the need for a new history of medicine that explored its impact on global society during the past 5,000 years. There have been several recent medical histories, including the excellent Man and Microbes: disease and plagues in history and modern times by Arno Karlen. However, Porter's book is the first to fill a lacuna in the general market. It covers world medicine, including Indian and Chinese, from 3000BC to the present. Porter is not unsympathetic to non-Western traditions, although more than half of the 700 pages is devoted to development of modern medicine.

What is particularly striking is how almost nothing could be cured before the mid-19th century. For 5,000 years, doctors practised medicine by offering patients a bedside manner and an explanation for their illness (wrong in every case) without being able to prevent, halt or eradicate disease. Whether patients were treated in the Hippocratic tradition, which was the first secular approach to medicine, or the Galenic, which promoted the concept of bodily humours, they had as much chance of survival on their own as in the hands of a doctor.

If anything, increased knowledge and confidence during the Enlightenment simply made doctors more proficient torturers. Voltaire would not allow himself to be touched by one, saying that they poured drugs of which they knew little, to cure diseases of which they knew less, into human beings of whom they knew nothing.

Once the nature of disease began to be understood after the 1870s, coupled with the mapping of human anatomy and the discovery of hygiene, doctors ceased to be mere props and became actual saviours. Invasive surgery became possible, vaccines proliferated, such as those for smallpox and rabies, which prevented thousands of deaths.

Yet progress is and always has been double-edged. Porter's major theme is the havoc wrought by civilisation and civilising agents. Cities, trade and foreign travel - the facilitators of knowledge and science - are also the breeding grounds of pestilence.

The Black Death originated in China and spread to Europe in the 14th century via Italian merchants who were fighting the Tartars in the Crimea. In the first known instance of germ warfare, the Tartars besieged the Italians' citadel and catapulted the corpses of plague victims over the walls. It proved a successful tactic: the merchants fled in ships to Genoa. Two years later, a quarter of Europe's population was dead.

European trade and travel famously brought devastation to indigenous peoples. The arrival of the Spanish on the Canary Islands in the 15th century wiped out the entire native population. Smallpox, measles and typhus decimated the Caribbean and the South American Indians, allowing a handful of Conquistadors to enslave a continent. The Hawaiians all but disappeared and the Tasmanian aborigines became extinct.

Although the British did not introduce cholera to India, their well-intentioned road and irrigation improvements helped the disease to kill millions of Indians as well as spread to the rest of Europe. Between 1847 and 1861, over a million Russians died from cholera. At home, the British suffered three cholera epidemics while falling victim to other diseases of industrialisation: TB, scarlet fever, chicken pox and rickets.

The onslaught of these catastrophes led to the social reformer Edwin Chadwick devising the first national public health programmes. Having discovered that the average age of mortality for labourers in Bethnal Green was 16, compared to 45 among the better off, Chadwick made the historic link between poverty and disease.

Colonial administrators in Africa took up Chadwick's campaign with zeal; indeed, some even argued that bringing tropical medicine to the natives justified the British Empire. But close inspection, Porter argues, shows that any benefit brought by Western medicine was largely incidental. War, migration, settlements, roads, railways, crop monoculture and even hospitals led to the deterioration of health and the spread of strange diseases from one tribe to another. Imperialism did not so much contain tropical disease as make it proliferate.

On the other hand, civilisation is essential for good health. In the 19th century, Rudolf Virchow was the first to place health within a socio- political nexus, arguing that the improvement of social conditions prolonged life. Political medicine, he wrote, consisted of education, freedom and prosperity. A century later, the economist Amartya Sen has observed that there has never been a famine in a free society.

Roy Porter would have no difficulty agreeing with Sen, while Sheldon Watts would no doubt reply that "freedom" is itself a political construct, that the notion of health is subject to Western ideology, and medicine is a dangerous tool in the hands of white people. Watts's Epidemics and History is a good illustration of the tyranny of theory, in this case the post-colonial Marxist kind. The late E P Thompson observed in The Poverty of Theory that the truth is the first victim of those who believe that "history can be constructed from a conceptual Meccano set". In any case, bashing the British for everybody else's ills is a perennially popular sport on many campuses.

Sheldon Watts is not coy about his prejudices: the only motivation for British contact with Africa and India was "white greed". There is no place in his ideology for altruism, ignorance, bad luck or ambiguity. Tropical medicine was nothing other than an instrument of empire. Health care in Africa was racist in its ideology, and furthermore executed at the whim of "profit-minded Britons" by the "gentlemanly Grand Assize of England (Parliament)".

Epidemics and History suffers from the monotonous purity of Cold War agit-prop theorising. For example, Watts repeats with total sincerity the Chinese claim that during the 1950s their "bare-foot doctors" eradicated all major diseases from the countryside, including syphilis and cholera. He entirely ignores the famine which accompanied Mao's Great Leap Forward.

If, for Watts, the future of Western medicine heralds further misery for other lands, the path is uncertain although more benign in Porter's view. Breakthroughs in the containment of disease have been offset by the rise of chronic illness. Health care is becoming increasingly expensive and intrusive; ordinary aspects of life such as menopause are being turned into medical conditions.

The impact of medicine on society is greater than ever before, and yet has never been so distrusted or regarded with such disappointment. The answer, Porter seems to say, is in understanding its limitations while never forgetting that, unlike any other approach, it works.