An Introductory Philosophy of Medicine

Chapter 2. Medical Causation and Realism

Causation and realism are two important notions that are essential for understanding any worldview, especially medical worldviews. The notion of causation refers to the act of bringing about or producing an effect (Horner and Westacott, 2000). In other words, causes are responsible for the fabrication or creation of events and entities within a given world. Causation is based on the principle that natural phenomena may have sources other than themselves, i.e. they need not be necessarily self-originating or self-generating. The notion of causation has had a tumultuous history in philosophical thought, especially with Hume's accusation that there is no necessary connection between cause and effect. Be that as it may, causation still plays an important role in almost any medical worldview with respect to knowledge and practice. Physicians and patients are both interested in the causes of diseases and poor health, as well as good health and wellbeing. Identifying a disease's cause is the first step often towards the possibility of treating a patient's diseased state or illness.

Realism, as a metaphysical notion, has also been vigorously contested during the history of western philosophy (Horner and Westacott, 2000). Today it pertains to the belief that there are real objects, especially at the level of the unobservable, which exist independent of the mind. In other words, reality is not reducible to a universal mind. Contemporary realism is a reaction to Kant's transcendental idealism, which claims that we cannot know reality in and of itself apart from our cognitive capacities, and to Hegel's absolute idealism, which asserts that mind is the supreme source for all knowledge and understanding. Although there are a variety of realistic positions, they are broadly divided into direct and indirect realism.' The different forms of realism share a fundamental belief in the existence of objects that exhibit mind-independent properties or qualities.

Antirealist positions deny one or both of these two fundamental features of realism: existence and/or mind-independence. Two important antitheses to contemporary realism are instrumentalism and constructivism. The former claims that reality is limited to entities observable to the unaided senses and that theories about unobservable entities are simply predictive or useful tools, while the latter claims that reality is simply a social construction based on a professional community's consensus of what constitutes reality. Like causation, realism also plays an important role in contemporary worldviews of medicine. Just as physicians and patients are interested in the cause of disease, so they are also interested in the actual or ontological status of disease and of the entities that cause them. A patient wants to know if he or she is really sick, as does the physician. In other words, can the disease-causing entity be identified and eradicated? In this chapter, the notion of causation is examined first, followed by the notion of realism.

2.1 Causation

Any discussion of causation in the western tradition must begin with the Greeks. In Metaphysics, for example, Aristotle (2001) distinguished four causes responsible for natural phenomena: material, formal, efficient or artificer, and final or teleological. His list represents a culmination of the pre-Socratics' and Plato's discussion of causation. The material cause involves the substance or matter out of which an object is made, while the formal cause pertains to the plan or design by which it is made. The efficient or artificer cause represents the agency or primary source responsible for making the object, while the final or teleological cause is the purpose or function for which it is made. For example, a table may be made out of wood by a carpenter. It may have a design of a flat square surface from which four legs are attached at each corner perpendicular to the plane's surface and is used to eat meals or to play cards. Francis Bacon (1561-1626) trimmed Aristotle's four causes to two, material and efficient, at the beginning of the scientific revolution in the sixteenth century (Bacon, 1994). By the seventeenth century moral philosophers debated issues concerning efficient causation, while natural philosophers were interested in material or mechanistic causation (Crane and Farkas, 2004).

Besides the trimming of the Aristotelian causes, the notion of causation became a contested issue in philosophy beginning with the seventeenth century. David Hume (1975) was responsible for initiating the debate over the notion among moral philosophers. Although Hume recognized that causation is "the cement of the universe," he claimed that there is no "necessary connection" between two events in terms of cause and effect. Rather, there is simply a "constant conjunction" between two events such that we impose a causal connection, with one being the cause and the other the effect. Thus, causation reflects cultural or social indoctrination. Immanuel Kant (1998) responded to Hume by situating causation as one of the principal categories responsible for "pure" understanding, especially natural or scientific understanding. For Kant, this category ensures the validity of scientific laws, in that human understanding imposes a causal relationship on scientific evidence in which phenomenal events are associated.

2.1.1 Contemporary Causation

Contemporary philosophers continue to debate the nature of efficient causation with no clear resolution in sight. They address two major questions with respect to efficient causation (Crane and Farkas, 2004). The first involves the type of entities that serve as causes and effects. For example, Donald Davidson (2004) claims that these entities are events that unfold or happen over time. "Much of what philosophers have said of causes and causal relations," argues Davidson, "is intelligible only on the assumption (often enough explicit) that causes are individual events, and causal relations hold between events" (2004, p. 410). However, David Mellor (2004) proposes a more expansive explication of causation and claims that causal entities are facts, which represent actual states of affairs, or particulars, which represent things or events.

The second question concerning causation involves the types of relationships between causes and effects. Contemporary philosophers discuss the nature of these causal relationships in terms of natural laws, as well as in terms of singular and probabilistic causation (Sosa and Tooley, 1993). Finally, the relationships between causes and effects are also discussed in terms of sufficient and necessary conditions, i.e. a cause may be adequate or required for an effect to occur (Humphreys, 2000).

Mellor (2004) identified four important "connotations" or criteria of causation, including temporality, contiguity, evidential, and explanatory. The temporal connotation or criterion involves the notion that causes generally precede the effects they evoke. The contiguous criterion includes the connection of the causes with the effects. The evidential connation pertains to the confirmatory support of the causes and the effects for each other. Finally, the explanatory criterion attests to the fact that causes serve to account for effects.

For Mellor, then, theories of causation must address both the temporal and spatial issues as to why causes must proceed and be contiguous with their effects. Also, such theories must "combine with our theories of evidence and explanation to say what makes causes and effects evidence for each other and how causes explain their effects" (Mellor, 2004, p. 424). Only by this means can a theory of causation be robust enough to account for causal relationships.

The nature of causation is also important to philosophers of the natural sciences, especially in terms of the discovery of causal relationships or connections among natural phenomena; for it is imperative that scientists distinguish between those entities that cause natural phenomena and those that do not (Humphreys, 2000). For philosophers of science, especially those advocating a "new experimentalism," controlled experiments represent a valid means of discovering causal relationships (Ackermann, 1989). By restricting independent variables, an investigator can determine not only the causal status of a dependent variable in terms of a natural phenomenon under investigation but can also determine the nature of the relationship between the cause and effect, i.e. whether it is linear or geometrical. But even this approach to efficient causation remains problematic for many contemporary philosophers.

Practicing scientists, however, do not concern themselves directly with the issue of efficient causation but rather with material causation, especially in terms of natural phenomena, which they take to be unproblematic. For example, Kenneth Rothman provides a typical definition for causation from a biomedical perspective: "A cause is an act or a state of nature which initiates or permits, alone or in conjunction with other causes, a sequence of events resulting in an effect" (1976, p. 588). Causation, in the natural sciences, is concerned with identifying the natural or physical acts or states that produce an effect. Moreover, a cause may be either sufficient or necessary. A sufficient cause is capable of eliciting the effect, while a necessary cause is required for educing it.

2.1.2 Medical Causation

Although a few diseases may be the result of a single sufficient and necessary cause, the majority of diseases are generally not the result of any single cause but rather of multiple causes (Rizzi and Pedersen, 1992). As Rothman states: "Most causes that are of interest in the health field are components of sufficient causes, but are not sufficient in themselves" (1976, p. 588). In other words, there is a constellation of causes that is responsible for a disease.

The causal relationship is not generally a simple linear relationship between cause and effect. That relationship is often complex and multifaceted (Montgomery, 2006). Sufficiency and even necessity in terms of disease causation are generally only partial. In other words, "we never have a full causal network or tree, but only a partial one" (Rizzi and Pedersen, 1992, p. 240). Many causes, whether sufficient or necessary, can be assigned a percentage in terms of their "etiologic fraction" for causing a disease. Thus, biomedical causation is seldom strictly deterministic but rather it is often probabilistic (Giere et al., 2006).

Causation within the biomedical model is generally attributed to physicochemical mechanisms.'- As noted earlier, mechanisms are composed of entities and forces that involve changes in the entities over time. As such, a mechanism is made up of entities and forces that interact with one another. Employing Machamer and colleagues representation of a mechanism, A-B-C, in which the letters represent entities and the arrows represent activities that provide the continuity in change or process of the mechanism from start to finish, a mechanism is a linear unfolding of one event after another. In this schema, the preceding letter, A, is often considered the cause of the proceeding letter, B, which is considered the result, with the arrow indicating the change or transition that takes place in the causal relationship or transformation. Moreover, mechanisms may be much more complicated with branching structures and feed-back and feed-forward loops. For example, the production of C may either amplify (feed-forward) or inhibit (feed-back) the production of B through A.

Finally, Rizzi and Pedersen (1992) proposed a useful taxonomy of causal factors in disease etiology, especially for diseases with multifactorial causes. The first category is the avoidable cause. In a causal nexus there are a variety of causal factors that are operative, which could be avoided or compensated for. They provided an example of a patient who after contracting mononucleosis, with an associated enlarged spleen, is counseled not to engage in strenuous physical activity but fails to heed the counsel and consequently suffers a ruptured spleen. Often many of these avoidable causes are the result of human error, whether in terms of skill or knowledge.

The second category is the impervious cause (Rizzi and Pedersen, 1992). This type of cause is unavoidable and usually the result of a pathophysiological process. With the above example, the enlarged spleen associated with mononucleosis is often unavoidable with respect to current medical practice. The final category is the susceptible cause. This type of cause includes examples of "potential and actual candidates for achievable therapeutic or prophylactic measures, factors that can be prevented or obliterated by intervention, factors that impede, impair or jeopardize the patient and are the declared objective of medical practice" (Rizzi and Pedersen, 1992, p. 252). In terms of treatment, for example, bed rest is a cause for recovery from mononucleosis. These categories of causes help, according to Rizzi and Pedersen, the biomedical practitioner to analyze the interactions involved in multifactorial disease causation. Henle-Koch Postulates

A classical example of biomedical causation in terms of mechanism is infectious disease. In the late nineteenth century, Jacob Henle (1809-1885) provided postulates, which were later modified by his pupil Robert Koch (1843-1910), needed to establish that a microorganism or parasite causes a particular disease (Evans, 1976). These postulates include: (1) the microorganism or parasite is present in every case of the disease; (2) it must be isolated from the host and grown under in vitro conditions; and (3) after being isolated and grown under in vitro conditions it must then be shown to produce or cause the disease by direct exposure to a healthful organism. In terms of a mechanism then, the causal relationship can be schematized as follows: A-B, where A is the microorganism that is responsible for B, the disease state, while the arrow represents the transition of the organism from a state of health to one of disease through the pathological agency of the microorganism.3

However, the above causal relationship is never quite as straightforward or simple, on first pass. According to Alfred Evans, "even at the time they were presented, the Henle-Koch postulates were never recommended as rigid criteria of causation and failed to apply to many diseases at the time when a causal relationship seemed almost unequivocal" (1976, p. 177). For example, a debate arose several decades ago over the application of these postulates to establish the causal agent for acquired immune deficiency syndrome or AIDS (Fujimura and Chou, 1994). Peter Duesberg (1988, 1997) claimed that the evidence for establishing human immunodeficiency virus or HIV as the causative agent of AIDS does not satisfy or fulfill the Henle-Koch postulates. Other researchers, however, argued that HIV does cause AIDS and that the evidence for it as the causative agent of AIDS does satisfy or fulfill the postulates (Cohen, 1994; O'Brien and Guider 1996). Hill's Criteria

Another problematic area of biomedical science in terms of establishing causation is epidemiology. For example, although cigarette smoking is considered a cause of lung cancer based on epidemiological evidence it is neither sufficient, in that not all smokers contract lung cancer, nor necessary, in that non-smokers contract the disease. Austin Hill (1965) proposed nine "aspects" or "viewpoints"-as he called them-or criteria-as they are called in the literature-for whether an association between two events is causative, based on epidemiological evidence. The first criterion is the strength of the association, i.e. the rate of increase in the appearance of the disease in the experimental group compared to the control group. The next criterion is the consistency of the association and involves the repeated observation of the disease by multiple investigators at different times and locations using different methodologies. The third criterion is the specificity of the association, i.e. the agent gives rise to a specific disease only and not to multiple diseases.

Hill's fourth criterion is the correct temporal relationship of events in the association between the agent and the appearance of the disease, i.e. the causative agent must precede temporally the appearance of the disease. The next criterion involves a biological gradient or dose-response relationship for the association between the agent and appearance of the disease. The sixth criterion is the biological plausibility of the association, especially in terms of current theory concerning the disease's mechanism. The next criterion is the coherence of the association with other known biological facts in the history of the disease. The eighth criterion is the availability of supporting experimental evidence, especially production of the disease in an animal model. The final criterion is the appeal to an analogous situation in which a causal relationship is previously established for the disease or a similar disease.'

The above "aspects" or "viewpoints" are standard criteria, although Hill cautioned against this term, to establish causation for many chronic diseases that have multiple causative factors or agents. For example, in the 2004 Surgeon General Report, Health and Smoking, the above "criteria" are used to judge that the association between cigarette smoking and lung cancer is causal (Carmona, 2004, p. 24). Consistency, for instance, pertains to a large number of retrospective and prospective studies that constantly demonstrate a link between smoking and lung cancer, while the biological gradient, for instance, involves a positive dose-response curve between the number of cigarettes smoked and the incidence of lung cancer in those who smoke cigarettes. Although the report acknowledges that judgments concerning causality under such circumstances are "always uncertain to a degree," still such judgments can be made "based on the totality of scientific evidence"' Evolutionary Causation

Nesse and Williams have recently championed a notion of evolutionary causation for disease, which answers the question of "why" concerning disease origins. Evolutionary causes are used to demonstrate "why humans, in general, are susceptible to some disease and not to others" (Nesse and Williams, 1996, p. 6). They contrast their notion to the notion of proximate causation, which answers the questions of "what?" and "how?" concerning disease origins. There are six categories of evolutionary causation, including defenses, infections, novel environments, genes, design compromises, and evolutionary legacies. These categories often intersect in terms of disease causation: "Novel environments often interact with previously invisible genetic quirks to cause more variation in phenotypes, some of it outside the normal range" (Nesse and Williams, 1996, p. 144). For example, a disease such as scurvy is a civilization disease in which vitamin C is absent from a modern diet.

According to Mel Greaves (2002), evolutionary causation of diseases revolves around the fact that genes that were at one time beneficial in terms of adaptation to the environment are no longer so because of changes in the environment. This is particularly true for cancer causation. Although the molecular and genetic components of cancer causation are important, they represent the proximate causal components; a fuller causal accounting requires historical and evolutionary components. "A key part of this argument," claims Greaves, "rests on the premise that certain normal (nonmutant) genes and gene variants or alleles selected in the past because they encoded functions that endowed survival or reproductive advantage now have the potential indirectly to increase cancer risk because of a change in the physiological context in which these same genes are now required to operate" (2002, p. 246). For example, breast cancer incidence is higher in western society, especially among Roman Catholic nuns, because exposure to estrogen is not broken by multiple pregnancies.' Humanistic Concerns

Although determining a distinct cause or causes of a disease is central for biomedical practitioners, humanistic or humane practitioners are less sanguine about it. For example, Cassell argues that the attempt to find a unique, mechanistic cause for a disease is ill founded or wrong headed: "although the desire to find a unique cause is natural, it stems from an incomplete view of how illness occurs" (1991, p. 109). Rather, illness results from a disruption in a living system. Cassell invokes insights gleaned from general systems theory to contend that efforts to determine a specific cause for an illness are ineffectual: "The contribution of general systems theory has been important in the growing understanding that illness cannot be viewed from the perspective of disease alone" (1991, p. 111). Illness is simply more than a disruption in the patient's physiology; rather, it also includes the psychological and social. He illustrates this point with an elderly man who is brought to the hospital with pneumonia. Recently widowed and suffering from a dysfunctional knee, he is unable to obtain the necessary nourishment and succumbs to the bacterium. The issue here is that the cause of this person's illness is multifactorial with no single cause predominating.

Stephen Toulmin also advocates an expanded notion of causation in medicine, to include not just the somatic but also the psychological and the social: "Philosophically speaking, there is no particular reason to select somatic factors as any more immediately relevant to or causative of human illnesses than all other kinds of factors and conditions involved" (1979, p. 68). For example, he cites the futility of treating a business person's ulcer through somatic intervention but ignoring the stress that comes along with the person's job. He then challenges physicians to include in their causative notion of illness the social issues that are responsible for illness: "if they are to develop a broader view of medical causation, they must also widen their ideas about the legitimate loci and modes of intervention, and so about their professional responsibilities: they may accept happily, for instance, the need to counsel their patients about their employment, styles of life, personal temperaments, and so on" (Toulmin, 1979, p. 68). Only then, can modern medicine overcome its myopic view of disease causation to address the suffering patient's experience of illness.

2.2 Realism and Antirealism

Just as the Greeks can be utilized to initiate a discussion on causation, so they can be used to begin one on the notion of realism (Horner and Westacott, 2000). Realism has its roots in the debate between Aristotle, who believed that investigations into the world reveal how the world really is independent of us, and Plato (427-347 BC), who believed that such investigations could not reveal the world as it is independent of us but only a copy of it. During the Medieval Ages, the debate centered on the distinction between realism, which involves mind-independent universals and their primary properties, and nominalism, which involves minddependent universals that exist in name only.

During the Enlightenment, however, realism was contrasted with idealism, the notion that there are only ideas formulated in the mind (Horner and Westacott, 2000). For idealists, such as George Berkeley (1685-1753), physical objects are simply a collection of sense perceptions and do not exist apart from those perceptions. Kant held that there is indeed a mind-independent world that can be known empirically (empirical realism) but that it is dependent on our way of knowing (transcendental idealism).'

Today, especially after logical positivism, realism is the philosophical notion that real entities exist independent of us and our perceptions of them. In other words, reality depends on the direct correspondence of facts with the way the world is. The notion of antirealism denies that there is a world independent of us and our perceptions of it or that there is a direct correspondence between facts and the way the world is.'

The two contemporary champions of these positions are Hilary Putnam (1977, 1990) and Michael Dummett (1978, 1991). Although Putnam began as a realist, he changed his mind and now advocates a notion of "internal realism," in which the real is bounded by a theoretical framework. Reality then is dependent upon such a framework, especially with respect to linguistic terms, and all talk outside this framework is suspect.' In contrast to Putnam, Dummett argues that realism is the position in which a statement's meaning is understood in terms of those conditions in which that meaning is true or real. Antirealism, the position he advocates, holds that a statement's meaning is understood in terms of the conditions that would simply warrant its assertion-nothing more.

Besides Putnam's internal realism and Dummett's antirealism, there are a variety of other realist and antirealist positions that play a significant role not only in philosophy but in other disciplines as well. The debate is important in the fine arts, for instance, with a variety of realist and antirealist positions. Realism, especially its absolute version, is rejected because criteria for determining representation are relative to cultural values. Recently, Dominic Lopes (1995) has proposed a pictorial realism that takes into consideration this cultural relativity. For Lopes, realism depends on the cultural system and its commitments to what needs to be communicated in terms of appropriate information: "We may say that systems are `appropriately informative' to the extent that they make commitments of the sort, which satisfy requirements as to the kind of information pictures should convey for the purposes they serve in given contexts" (1995, p. 283). For example, impressionist pictures are realistic to viewers who hold a specific perspective to what sorts of information a picture should represent.10 Although the above forms of the realism/antirealism debate are interesting and instructive, the following discussion is limited to the positions of direct, representative, critical, and scientific realism and to the antirealist positions of instrumentalism and constructivism, after which I discuss realist and antirealist positions in medicine.

2.2.1 Realism Direct or Naive Realism

Direct or naive realism is motivated by common sense, in that when an object is perceived within a definite location there is no need, most of the time, to justify its existence. Proponents of this position state "that our claims about the world are made true or false simply by the way the world is, independently of our cognition of it" (Horner and Westacott, 2000, p. 37). In other words, our senses provide us direct access to or immediate contact with the world. A major appeal of direct realism is that "it denies a foothold to sceptical doubts about the match between our subjective experiences and objective reality" (Horner and Westacott, 2000, p. 37). However, this appeal is not completely warranted or unproblematic.

Although direct realism appeals to a common sense that appears immune to skepticism, uncritical or naive common sense is often deceived. For example, common sense held for centuries that the earth is flat. Moreover, Descartes claimed that although he sees a hooded figure crossing the street he does not know if it is a person or a robot. Consequently, perceptions are subjective and depend on additional evidence to confirm their veracity. Direct realism fails because ultimately there is no immediate access to objects; rather, that access is mediated or determined temporally and spatially by the senses. Representative or Representational Realism

Representative or representational realism takes into consideration the mediation of sense perception when examining reality. Its contemporary roots are in the seventeenth century, in which Descartes and John Locke (1632-1704) distinguished between an object's primary and secondary qualities. The primary qualities are those that really do belong to the object itself, while the secondary qualities are not the object's intrinsic properties. Examples of primary qualities include motion, quantity, shape, and extension in space, while examples of secondary qualities include color, taste, and smell.

Representative realism is the position that "our sense-perceptions are caused by independently existing physical entities possessed of physical properties describable in a language of mathematical physics, and that these properties can be inferred from our sense-impressions" (Horner and Westacott, 2000, p. 42). This realistic position differs from naive realism by holding that our sense perceptions do not give us direct access to the way the world is but are derived or inferred from those perceptions. However, it also differs from idealism in that our knowledge of the world is not simply a mental construct apart from the object.

Although representative realism seems plausible enough, a problem arises as to whether sense perception, even of an object's primary qualities, permits an inference of its existence; hence, as for direct or native realism errors and illusions remain a problem for this type of realism. Specifically, there is no sense-independent means to justify an object's existence. This is no easy problem to resolve, if it can be resolved at all. Critical Realism

Critical realism, a successor to representative realism, is an attempt to resolve its predecessor's problem of errors and illusions. Unfortunately it has many versions, especially in the United States and the United Kingdom, although it is most commonly associated today with Roy Bhaskar.I I Fundamentally, proponents of critical realism propose that mental or cognitive activity plays a mediating role in understanding the world. "One could fashion an account of mental mediation that did not involve the pitfalls of Lockean representationalism," notes C.F. Delaney, "by carefully distinguishing between the object known and the mental state through which it is known" (1999, p. 194).

Roy Sellars, who coined the term in 1916, claimed that the central tenet of critical realism is: "knowledge of external things and of past events is an interpretation of these objects in terms of understood predicates and does not involve the literal presence of these objects in the field of consciousness of the knower" (1927, p. 238). In other words, objects do exist apart from their perceptions but, at the same time, are contingent upon personal and cultural factors.

Critical realism is a philosophical view that asserts a mind-independent world, but a world that changes as our knowledge of it develops-what Sellars called "a reinterpretation of the nature of knowledge" (1927, p. 238). Consequently, error and illusion can be explained in terms of development or reinterpretation. For Sellars and a few other critical realists mental mediation is material in nature, while for others it is not. Although critical realism helps to defend realism, its account of the mental vis-a-vis psychological sciences is problematic since science itself is often undergoing revision. Scientific Realism

Scientific realism, which developed in response to logical positivism's branding of the realism question as metaphysical and therefore a pseudo-question, is the position that "science provides us with a true picture of independently existing reality" (Homer and Westacott, 2000, p. 112). Scientific realism and its antithesis, antirealism, have recently dominated much of the discussion in contemporary science studies, especially in terms of the antirealist positions of instrumentalism and constructivism (Devitt, 2005)."

Richard Boyd (1991) has identified four key features of scientific realism, based on the notion that science's technological or instrumental success depends upon theories in which the terms refer approximately to the real nature of the world. The first is that the theoretical or unobservable terms of a scientific theory represent actual entities. In other words, these terms should be interpreted in a realistic manner. The next feature is that scientific theories can be and often are confirmed by experimental procedures and other observational means. Although the confirmation is not absolute, it is approximate or probable. This leads to the third feature. As evident from the history of science, a mature science's progress may be interpreted as asymptotic, i.e. coming closer and closer to the way the world really is. In fact, theories build upon one another in a march towards unpacking reality in terms of scientific investigations. The final feature is that the "reality which scientific theories describe is largely independent of our thoughts or theoretical commitments" (Boyd, 1991, p. 195).

A traditional defense of scientific realism is the "no miracle" argument (Smart, 1963b). "According to this argument, it would be an extraordinary coincidence if a theory that talks about electrons and atoms made accurate predictions about the observable world-unless electrons and atoms actually exist" (Okasha, 2002, p. 63). In other words, realists claim that antirealists must invoke the miraculous to account for the theoretical and technological success of science. Antirealists, however, claim that the "no miracle" argument is also supportive of their position. They argue that an equally valid-and probably a more parsimonious-interpretation of the success of science, than the truth of theories and their entities, is that science is simply on the right path for empirical success.13

Besides the objection to the "no miracle" argument, antirealists object to scientific realism on two other fronts. The first is that many past scientific theories and their entities are no longer accepted by the contemporary scientific community. This objection is called "pessimistic induction" and relies on the historical record, which is replete with case studies demonstrating the fallibility of scientific theories and the fictional nature of theoretical entities. For example, Larry Laudan (1981) lists dozens of theories that were at one time accepted by the scientific community only to be refuted through later development, with the classic example being phlogiston. Realists accept that the historical record demonstrates that many scientific theories are eventually proved wrong; but they still claim overall that scientific theories that replace the wrong ones more closely approach reality.

Antirealists level another objection against scientific realism-the underdetermination thesis, which asserts that empirical evidence is unable (in principle) to justify a theory vis-n-vis competing theories. Antirealists claim that if evidence cannot justify any one theory, then it is questionable whether one can accept the existence of theoretical entities or the truth of scientific theories. Realists counter by stressing that the underdetermination thesis also applies to observable entities and the criticism is thereby arbitrary.

There are several types of scientific realism, often proposed in response to antirealist criticism, depending on whether the emphasis is on the metaphysical (existence) dimension of the world or on its epistemological (truth content) dimension (Devitt, 2005). A popular form of scientific realism is "entity" realism, especially championed by Ian Hacking. "Scientific realism," according to Hacking, "says that the entities, states, and processes described by correct theories really do exist" (1983, p. 21). In other words, the entities proposed in scientific theories, like atoms, molecules, and genes, are real, especially if these entities can be manipulated experimentally. In a well known passage on altering the charge of a niobium ball by spraying it with either positrons or electrons, Hacking asserts: "So far as I am concerned, if you can spray them then they are real" (1983, p. 23). Antirealists argue that this form of realism relies on the precarious nature of unobservable entities and claim that there is a divide between the observable and the unobservable. Antirealists distrust the unaided senses for populating the world with unobservable entities.

For scientific realists theoretical entities, although unobservable to the unaided senses, are as real as observable entities such as organisms and planetary bodies. Realists claim that the goal of science is to provide an understanding of nature in its entirety, while antirealists claim that that goal is to provide an understanding only of nature that is observable to the unaided senses. Grover Maxwell (1962) criticized the observable/unobservable distinction that antirealists rely on, by arguing that there is a gradation from the observable to the unobservable. Beginning with unaided vision, he progressed from sight through a glass window to more sophisticated aids such as the microscope and asked at what point one should no longer trust unaided vision. His point was that the aided/unaided distinction for the senses is arbitrary and does not automatically preclude scientific realism.

2.2.2 Antirealism Instrumentalism

Although scientific realists claim that scientific theories provide a window into reality, the advocates of instrumentalism counter that theories do not provide such access. An instrumentalist is "one who holds that theories are tools or calculating devices for organizing descriptions of phenomena, and for drawing inferences from past to future. Theories and laws," Hacking adds, "have no truth value in themselves. They are only instruments, not to be understood as literal assertions" (1983, p. 63). Instrumentalists are not concerned with truth but with the pragmatic results of making predictions and either confirming or refuting the prediction through observation. The celebrated physicist, Stephen Hawking, argues, for example, that it is "meaningless to ask whether [a physical theory] corresponds to reality. All that one can ask," he claims, "is that its predictions should be in agreement with observation" (Hawking and Penrose, 1996, p. 4). Instrumentalism is thus a challenge to the very nature of what the world is like and is incommensurable with scientific realism. Constructivism

Constructivists also challenge realism in terms of the nature of scientific theories and their entities. For realists, reality is discovered and there is a causal link between reality and its discovery. It is this causal link that social constructivists object to most.14 For example, Bruno Latour and Steve Woolgar in their pioneering book on scientific practice claim: "we do not conceive of scientists using various strategies as pulling back the curtain on pregiven, but hitherto concealed, truths. Rather, objects ... are constituted through the artful creativity of scientists" (1986, p. 129). Latour and Woolgar do not question the "solidity" of facts, but they do argue that "facts are thoroughly understandable in terms of their social construction" (1986, p. 107). For them, reality is not the cause of scientific facts or knowledge; but rather it is the consequence of this knowledge. Thus, reality as represented in the natural sciences depends thoroughly-or might we say only-on the process of social construction.

2.2.3 Medical Realism and Antirealism

Realism and antirealism are also debated in the philosophy of medicine literature, although few commentators subscribe to direct or representational realism. In discussing the role of the bacterium Helicobacter pylori in ulcers, for example, Paul Thagard defines medical realism accordingly: "By the term medical realism, I mean that disease and their causes are real and that scientific investigation can gain knowledge of them" (1999, p. 81). This notion of medical realism is a subset of scientific realism, because the components of the medical world, such as bacteria, instrumentation, and experimentation imitate scientific practice.

Thagard defends medical (scientific) realism on four counts. The first is the "recalcitrance of experimentation," in which medical scientists often obtain unexpected experimental results that are publicly reproducible. Next is the "reliability of instruments," in which "instruments provide robust results across different social groups" (Thagard, 1999, p. 239). Third is "causal efficacy of theory," in which well confirmed theories have pragmatic consequences for treating diseases. Finally is the "realist nature of scientific discourse," in which medical scientists talk about medical entities and causes in realistic terms.

Thagard also contrasts medical realism with the competing antirealist positions of empiricism, conceptualism, and social constructivism. Empiricism, a species of instrumentalism, is the position that only objects that are visibly observable are real and scientists should restrict reality claims to the visibly observable. So diseases like ulcers are real since they are observable, but the bacterial entities responsible for them are not. Conceptualism, a form of idealism, is the position that the history of the natural and medical sciences reveals that progress is not towards the true or real. Rather, that history reveals paradigm shifts in which the paradigms are often incommensurable with one another (Kuhn, 1996). Finally, social constructivism is the position that medical and scientific knowledge, hence the real, is the result of a social consensus within the appropriate medical and scientific community.

William Stempsey proposes a form of realism-value-dependent realism-for medical practice, particularly diagnosis, that mediates between scientific realism and social constructivism. "The value dependent realism I am advocating," writes Stempsey, "recognizes a reality that exists independent of our theorizing, but a reality that is necessarily dependent upon some particular conceptual apparatus if it is to be described. Reality," he continues, "may allow more than one empirically adequate description of it" (2000, p. 48).

Stempsey is committed to a realist position because people contract diseases and die from them. The reality of the illness experience is foundational. "We want our view of disease to reflect," asserts Stempsey, "the reality of an individual's pain and suffering as much as we want it to reflect the research in the basic sciences that have made Western medicine so empirically successful in treating disease in the twentieth century" (2000, p. 32). To that end, both facts and values are critical for understanding disease process and the patient's illness experience. "Value-dependent realism," argues Stempsey, "bridges the fact-value gap in its recognition that values are necessary for the determination of what the facts are. In a framework adequate to explain the concept of disease, classification of disease, and the diagnosis of disease, values," he concludes, "are as necessary as facts" (2000, p. 33).

Humanistic practitioners may often subscribe to one of the antirealist positions. For example, Cassell advocates a version of conceptualism: "diseases are not real things in the manner they are generally conceived to be. Disease," he continues, "are real in the same sense that ideas are real, concepts are real, and categories are real" (1991, p. 105). In other words, diseases are not independent entities such as bacteria; rather, they are abstractions or concepts that cannot be directly observed by the physician. As abstractions or concepts, diseases represent the complete manifestation of the pathophysiology: "Only the sum total of the expressions of the disease in this instance has actual touch-them-with-your-hands existence" (Cassell, 1991, p. 105). He, therefore, subscribes to conceptual antirealism. His aim is to reverse the overly objectification of disease in the biomedical model, which has made the disease often more real than the patient.

2.3 Summary

Medical causation and realism are notions that entities, such as patients, diseases, bacteria, are real, mind-independent objects, which occupy a medical worldview, and that there are causal connections among them. These notions are generally below the surface of the proceeding philosophical discussions concerning the patient as body or person, disease entities or health states, and diagnosis and therapeutics, which are discussed in the remaining chapters of Part I. The question, for instance, over whether disease entities such as bacteria and the infectious diseases they bring about or cause are real or not is a contested question.

Most biomedical practitioners subscribe to a notion of realism, especially scientific realism, in which the entities of the medical worldview are believed to be real or that there is a direct correspondence or immediacy between what we think the world is and the way the world actually is. Thus bacteria are real entities and are responsible for or cause real diseases.

Many humanistic practitioners subscribe to an antirealist position or, at least, to a weak form of realism, in which either non-visible entities like bacteria and notions like diseases are not real but abstractions and that disease causation does not involve simply an invocation of a single agent but multiple agents. Humane practitioners, like Cassell, subscribe to antirealism in order to reinstate the patient into medical practice. In this sense they address the quality-of-care crisis brought on by biomedicine's realism, which focuses more on the disease rather than the patient's experience of illness.

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