Before embarking on a discussion of the philosophy of public health, it is important to be clear on terminology and scope. "Philosophy" means how and what people think about basic and longstanding human concerns such as knowledge, reasoning, free will, morality, objectivity and rationality, facts and values, and freedom. Although philosophy is often discussed at abstract "high ground" levels, this chapter will provide philosophy at a level much closer to everyday concerns. Call it the userfriendly "middle ground" level (Blackburn, 1999). It is important to make philosophy matter—to connect it—to how we think about and practice public health.
"Public health," like philosophy, is not easy to define. A recent definition states that "public health is the prevention of disease and premature death through organized community effort" (Beauchamp, 1995). This is a good but narrow definition, omitting prevention activities that have been historically important at the individual level, say between physician and patient. It also ignores injuries and other preventable conditions not traditionally considered diseases. However it is defined, public health is a complex force in society.
Combining philosophy and public health is like creating a giant tapestry from an inexhaustible supply of threads. Weaving philosophical concerns into the fabric of public health can look like this: knowledge is generated in the form of objective evidence from studies in biology, epidemiology, and social science; these facts provide a rational basis for undertaking interventions designed to prevent disease, injury, or death; these actions also reflect community values—some communities constrain an individual's freedom in the name of the common good. For example, U.S.-based airlines do not permit smoking, reflecting U.S. health concerns and policies. Other communities do not ask the same of their members—smoking is permitted on many international airlines.
PROBLEMS FOR THE PHILOSOPHER OF PUBLIC HEALTH
Making sense of contradictory community values is only one task for the philosopher of public health. There are conceptual problems, including ontological concerns such as defining health, disease, and causation. There are problems of knowledge, logic and scientific discovery, including epistemological concerns such as the absence of rigorous proof or disproof (underdetermination) and the nature of causal inferences. And there are problems of goodness and action; such as ethical concerns about how public health interventions reflect beneficence and how they address conditions of social and environmental justice. A central ethical problem is the extent to which individual autonomy is constrained in the name of the common good when public health interventions are implemented.
These sorts of problems can be illustrated in real-life situations, such as case studies that reflect the complex context of contemporary society. Public health, for example, is closely connected to both science and medicine.
CASE STUDY
Suppose that a few days after returning from an out-of-town trip, you feel acutely ill. You have a high fever, productive cough, and a vague sense that things will get worse before they get better. You drive to a clinic for treatment where you are examined by nurse and physician alike, who ask and probe and listen to your story and prescribe pink pills that you swallow with water from the drinking fountain. Driving home, you consider the doctor's suggestion to participate in a research study of overweight former smokers. She said that you have an increased risk of cancer and that the research will test whether that risk can be reduced by adhering to a diet high in special nutritional compounds, regular exercise, and screening tests. "Free treatment, if it comes to that," she said. "Why should I participate?" you asked. "Will it prevent cancer? Will I lose weight?" "Hard to say," she replied. "At best, we'll learn how to prevent cancer in our community. We have very high rates here. We do the science so that we know what is the best thing to do for many people."
As you experience these events, you stepped into the Venn diagram—the overlapping intersection—of public health medicine, and science. Medicine and public health both rely upon nearly identical definitions of health and disease.
Medicine and public health rely largely upon the same types of scientific studies. Medicine and public health apply scientific knowledge to individuals and populations, respectively, and thus create both opportunities for doing good and for doing harm.
There are also stark contrasts between medicine and public health. Medicine treats the sick individual; and it has the physician-patient relationship at its core. Public health prevents illness and injury in populations. The conditions under which interventions are undertaken may also be quite different. Public health actions are precautionary in nature, using available scientific evidence as a warrant. Public health involves the diffusion of information through communities empowered to help themselves, often with little input from health professionals.
Making sense out of these complex arrangements between public health and medicine and science is a major task for those who "think" about the philosophy of public health.
WHY PHILOSOPHY MATTERS
Philosophy matters because it helps us to better understand the problems of public health and how they are connected to the problems of medicine, science, and society. It can help to make clear what is meant by health and disease. Centuries ago, some conditions were believed to be the visitations of evil sprits, and today we believe them to be caused by microscopic organisms. And we "know" that our current belief is a better belief, based on using scientific tools and techniques. Philosophy, when connected to history, helps us to understand the significance of these and future changes in knowledge. What we "know" today about genes and cancer, lifestyles and heart disease, and environmental exposures and asthma will evolve, as history indicates, into something different.
What are the causes of disease? How shall we go about discovering them? These are key public health questions with important links to longstanding discussions in science and in philosophy. When is disease prevention a good thing to undertake? How can we best balance the risks and the benefits of intervening? What will society gain (and lose) from successful prevention efforts? These are central questions not only for the public health practitioner but also for the philosopher of public health. Each may start their "think" on these questions at slightly different places, but each has a compelling interest in complementary answers.
The public health practitioner examines the known causes of a disease and the impact of interventions, and then implements appropriate actions. The philosopher examines how the concepts of cause and prevention have evolved over the years, how uncertainty and the relationship between hypothesis and evidence influence the process of discovery, and may also declare a set of guiding general ethical principles that apply when implementing preventive interventions in specific cases. Yet, regardless of where the inquiries of practitioner and philosopher begin, they should be intertwined. It matters how a cause is defined and how we judge it to be present when we decide to intervene to prevent disease. It matters that an intervention designed to control disease or early death may result in harm to some exposed to it; this is a central problem in the ethics of public health screening programs. And it matters that public health relies upon the social fabric of a community—including powerful medical, legal, and political forces—to get much of its work done.
PUBLIC HEALTH'S PHILOSOPHICAL JOURNEY
Causation, ethics, science, and society are some of the signposts along public health's philosophical journey. Imagine three traveling companions— a citizen, a public health professional, and a philosopher—each asked to comment upon a government regulation requiring communitywide testing of a disease marker. The citizen may respond, "How can the government tell me what I must do with my body . . . and how do I know this screening will do me any good?!" The public health professional may respond, "What is the scientific evidence that the test finds early disease, and how certain are we that early treatment is a cost-effective way to reduce mortality in a community?" The philosopher, in turn, may ask, "What moral maxims warrant a decision requiring such screening, and how are they connected to the principles of autonomy and beneficence, theories of justice and utility, and the ever-present uncertainty of scientific knowledge?"
Public health, with its core concepts of prevention, community, methodology, disease, and health, and with its strong ties to science and the humanities, will benefit from philosophical inquiry when these three travelers find ways to help each other answer their respective questions. The precise nature of that extended conversation may include abstract "high ground" general theories, but it can also be conceived as an approach to problem-solving that connects longstanding human intellectual concerns, that connects the goals and activities of communities, that, and most importantly, affects the health of the human population.
THE PHILOSOPHICAL BASIS OF PUBLIC HEALTH
The philosophy of public health cuts across the realms of ontology, epistemology, and ethics as it strives to make sense of what public health is, what knowledge it can claim, and whether efforts to change the determinants and distribution of disease in the name of the common good are warranted. A core concern of a philosophy of public health is the balance between the interests of communities and populations and those of individuals. These interests spring from two complementary and essential public health goals: the prevention of disease and the promotion of health and well-being.
Scientific method, analysis, and synthesis play key roles in a philosophy of public health. Systems, theories, and models of disease causation are among its central explanatory themes. Public health relies upon the creative forces of scientific discovery and the accumulation of objective knowledge that rests upon a foundation of probabilistic events. Uncertainty runs through it like a river. Hypotheses ranging from the molecular constructs of biology to the dynamic forces of society will be tested by quantitative and qualitative methodologies representing distinct yet connected scientific disciplines. Despite the heavy weight of paradigmatic pressures, the methods of public health science are dynamic. Underdetermination, a fundamental state of evidentiary uncertainty, will plague strong inferences. Consensus on reasoned judgments from available scientific evidence will determine when preventive actions should be undertaken and by whom and at what cost.
Public health is soaked with values; and most often, those of the common good will be paramount. The philosophy of public health incorporates the values and traditions of communities and of relevant professions, providing an intellectual foundation for organized action to reduce suffering and promote well-being. The philosophy of public health will provide a guide for understanding how beneficent and precautionary actions can and should occur, tempered as they are by the global diversity of cultures, the complex interactions of human society with natural and constructed environments, and fundamental human rights.
Although a unique entity, the philosophy of public health is closely connected to political philosophy, economics, history, and law, just as it is connected to bioethics, and the philosophies of science, biology, and medicine.
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