Yet most people's senses tell them that society is getting less healthy and more dangerous. Every day we find ourselves faced with a new health panic about cancers, allergies or unsafe food. We seem constantly at the mercy of new and often frightening diseases, from Aids to Ebola. Old diseases which we thought had disappeared or been brought under control - such as TB - are back with a vengeance. Medical advances, such as IVF or cloning, often create fear as much as hope.
This paradox of an age in which medicine seems to have triumphed, and yet is seen to have failed, lies at the heart of Roy Porter's The Greatest Benefit to Mankind. To understand the contradictory nature of contemporary medicine, Porter suggests, we have to understand its historical context, and the evolution of the relationship between medicine and society.
This is a monumental work. Nearly 800 pages long, it roves over more than 2000 years of medical history, and over several continents. But Porter's deftness in synthesising both historical and technical material, and his ability to give flesh to his arguments, turns what might have been a stolid narrative into an enthralling story.
He begins his medical odyssey in Ancient Greece with the first attempts to replace supernatural with naturalistic explanations for disease and illness. From Hippocrates to Galen, the great Roman physician of the second century, the medicine of antiquity stressed the correlations between the healthy human body and the harmonies of nature. Illness was an imbalance of the four humours of bodily fluids (blood, phlegm, choler and black bile) and the task of medicine to restore that balance.
The Greco-Roman tradition was transmitted to Islam and then back to medieval and Renaissance Europe. But while Renaissance medicine drew on classical traditions, such as the idea of health as humoural balance, it also helped to undermine them. The finest achievement of Renaissance medicine - William Harvey's demonstration of the circulation of the blood - was in direct contradiction to the claims of Galen.
The new medicine did not simply overturn old theories of bodily function, it postulated a completely different way of understanding illness. At its root was the belief that medical knowledge could be attained by probing ever-more deeply into the body, a belief that laid the foundations for the later edifice of scientific medicine. Rather than understand life in relation to the wider cosmos, as in traditional medicine, Western medicine has concentrated on the individual self and explained sickness in terms of the body itself. While such an approach helped medicine triumph over many areas of illness and disease, Porter argues, it also helped dehumanise medicine, leading eventually to the backlash against orthodox medicine that characterises contemporary society.
Many historians would question the wisdom of such a medical narrative. In recent years, there has developed a backlash against "Whig" history - the idea that history demonstrates an inevitable, linear development to the present. Instead, a more relativist approach has become fashionable. Drawing particularly on the work of Michel Foucault, medical historians have increasingly argued that different theories and practices of healing are not part of a continuous road to ever-increasing knowledge. Rather, each is a distinct product of its own time, and cannot be understood outside its particular historical or social context. Hence, the humoural theory of antiquity is no better or worse than modern physiology, simply different in its understanding of the body. The reason Western medicine has gained such dominance, the relativists argue, is not because it is better than other forms of healing, but because the West enjoys such economic and political power over the rest of the world.
Porter is rightly wary of such arguments. He is certainly sensitive to what E P Thompson called "the enormous condescension of posterity" - the tendency to judge the past using the criteria of the present. But, as Porter puts it, "eschewing history by hindsight does not mean denying that there are ways in which medical knowledge has progressed". Harvey's theory of circulation was right; Galen's was wrong. Hence one is better than the other and demonstrates progress in medical thinking. And while Porter acknowledges that Western power has allowed the "ceaseless spread throughout the world" of Western medicine, equally important, he points out, is the fact that such medicine "works". This is why "what began as a medicine of Europe is becoming the medicine of humanity". Indeed, to talk of "Western medicine" smacks of condescension towards non-Western peoples and societies who have both appropriated and developed modern scientific medicine.
Nevertheless, Porter remains ambiguous about the idea of medical progress. The balance sheet of modern medicine, he writes, is difficult assess because civilisation has at every step brought health costs as well as medical benefits. The agricultural revolution, for instance, allowed humanity to dominate the planet, but also created a "disequilibrium between production and reproduction that provoked later Malthusian crises", and unleashed diseases that were once exclusive to animals. Similarly, industrialisation created urban slums that became breeding grounds for rickets and TB.
It is true that historical development has often brought mixed blessings. But there is a danger here of conflating social change and technical progress. Consider, for instance, Porter's claim that Western medicine has had a double-edged impact on the peoples of the Third World because of the depredations of imperialism. "The good that Western medicine did [for the Third World] was marginal and incidental," he claims. "It formed, however, an integral part of the ideological baggage of empire." "The imperialism latent in Western medicine," Porter adds, "was obvious in its attitudes towards indigenous healing: it aimed to establish rights over the bodies of the colonised."
This seems a somewhat perverse reading of history. Certainly, imperialism ravaged, and continues to ravage, the health of the Third World. The biggest killer of children in the world today is diarrhoea. Clean water supplies could at a stroke solve this epidemic. The lack of Third World development means that even such basic needs remain unmet. But, however much imperialism may have impoverished the Third World, it seems difficult to deny that medical science has brought tremendous gains, for example through vaccination against diseases such as diphtheria and polio.
Ultimately, the debate about medical progress is really a debate about whether one views a glass as half empty or half full. Take what is perhaps medicine's finest achievement this century - the development of antibiotics. Critics of orthodox medicine argue that the evolution of drug-resistant strains of bacteria and viruses shows the failure of medicine to live up to its promises. Half a century ago, however, all microbes were drug resistant, as there were no drugs for them to resist. Whatever the new problems created by drug-resistant microbes, antibiotics are a triumph of medical progress. That such a triumph is now widely seen as a fable about the limits of human intervention surely tells us more about our pessimistic age than about the nature of medical science itself.
Perhaps the least satisfactory aspect of Porter's narrative is his analysis of the "medicalisation" of society. The success of medicine, Porter argues, has allowed it to expand its empire. Traditionally, the physician simply patched up the sick individual. But over the past two centuries, medicine has gradually asserted a more central role in the ordering of society, staking claims for a mission in the home, the workplace and the law courts. Medicine transformed from being a negative enterprise of healing the sick to being a positive project of health promotion - of keeping an eye on the healthy to ensure that they do not succumb to sickness through poverty, ignorance or inappropriate behaviour. The result, Porter argues, has been the creation of a "therapeutic state". This has led to "inflated expectations" of medicine which, when unfulfilled, have created disenchantment. "Medicine," Porter believes, "will have to redefine its limits even as it extends its capacities."
This suggests that medicine can put its own house in order. Yet it seems clear that the roots of the dilemmas facing medicine lie elsewhere. On the one hand, in an increasingly atomised society in which traditional moral standards are breaking down, the promotion of healthiness has become a useful way for the state to reassert social control - witness how panics, from Aids to cigarettes, are used to regulate behaviour. On the other hand, in an anxious and fretful age, many people view social issues in terms of personal survival. The result is what the late Pietr Skrabanek called "a cult of healthism". As he put it, "a dying century and a dying culture makes war against death its main preoccupation".
The predicaments of contemporary medicine, then, are fuelled by wider social developments: that is the central theme of The Greatest Benefit to Mankind. The history of medicine, Porter writes, must be understood as "The symbiosis of disease with society, the dialectic of challenge and adaptation, success and failure". One may not agree with all Porter's answers to the dilemmas facing contemporary medicine, but his magnificent book nudges us towards asking the right questions.
! 'The Greatest Benefit to Mankind: A Medical History of Humanity from Antiquity to the Present' by Roy Porter is published by HarperCollins at pounds 24.99