ESTUDIO COMPARATIVO DE CTPH Y DBUSE DE LOS PACIENTES CON ICTERICIA OBSTUCTIVA DE ORIGEN MALIGNO TRAS CPRE FALLIDA

The reflexive model introduced in Chapter 6 differs from conventional models of perception on one fundamental point. In terms of phenomenology, objects and events as perceived and percepts of those objects and events are one and the same. Chapter 7 examined how this insight can be incorporated into a critical realist theory of knowledge. In the present chapter we examine some of the consequences for a science of consciousness.

Public, objective, physical science

Following the implicit, dualist separation of objects as perceived from percepts of objects illustrated in Figures 6.2 and 6.3, it is generally taken for granted within psychology and philosophy that percepts of objects (and other contents of consciousness) are private, subjective and observer dependent (their existence depends on the mind of the observer). This is commonly thought to impede their investigation. By contrast, the physical objects we see around us are public, objective and observer independent (they exist independently of the mind of the observer).1 _{In the words of the philosopher Curt Ducasse,}

In the case of the things called ‘physical,’ the patent characteristic common to and peculiar to them, which determined their being all denoted by one and the same name, was simply that all of them were, or were capable of being, perceptually public—the same tree, the same thunderclap, the same wind, the same dog, the same man, etc., can be perceived by every member of the human public suitably located in space and in time. To be material or physical, then, basically means to be, or to be capable of being, perceptually public.

(Ducasse, 1960, p. 85) Given its grounding in publicly observable events, many also believe that physical science can provide objective knowledge. That there is something to explore which can be known in a public, objective way is supported by the fact

that the edifice of science is constructed by different individuals at different times and in different geographical locations. As the philosopher of science Alan Chalmers notes,

The theoretical structure that is modern physics is so complex that it clearly cannot be identified with the beliefs of any one group of physicists. Many scientists contribute in their separate ways with their separate skills to the growth and articulation of physics, just as many workers combine their efforts in the construction of a cathedral. And just as a happy steeplejack may be blissfully unaware of some of the implications of some ominous discovery made by labourers digging near the cathedral’s foundations, so a lofty theoretician may be unaware of some new experimental finding for the theory on which he works. In either case, relationship may objectively exist between parts of the structure independently of any individual awareness of that relationship.

(Chalmers, 1992, p. 116) In his book Objective Knowledge, the philosopher of science Karl Popper makes the added claim that the logical content of books, and the world of scientific problems, theories and arguments forms a kind of ‘third world’ of objective knowledge,2 _and

knowledge in this objective sense is totally independent of anybody’s claim to know; it is also independent of anybody’s belief, or disposition to assert, or assert, or to act. Knowledge in the objective sense is knowledge without a knower; it is knowledge without a knowing subject.

(Popper, 1972, p. 109)

Public, objective, psychological science

Given the success of physical science, along with its promise of ‘objective knowledge’, it is not surprising that much of psychology tried to mould itself in its image, particularly in the behaviourist period (see Chapter 4). This attempt to ‘objectify’ both the contents and the methods of psychology extended even to areas that dealt directly with subjective experience, such as psychophysics. Psychophysics tries to discover the precise ways in which the stimuli described by physics are mapped into experiences of those stimuli. Physical descriptions of the stimuli can be obtained using standard scientific techniques (instruments that measure intensity, frequency and so on), but these techniques do not allow one to access (let alone measure) conscious experiences. To avoid a return to ‘experimental introspectionism’, twentieth-century psychologists consequently tried to translate conscious experiences into externally observable, quantifiable

responses (to ‘operationalise’ conscious experiences). In some writings this was combined with an attempt to redefine conscious experiences (of subjects) in terms of the operations used to measure them—and, for consistency, this redefinition also had to apply to the experiences of the experimenters. The psychophysicist S.S.Stevens argued, for example, that

The study of sensation divests itself of many tangles, provided the distinction between the experimenter and experimentee is carefully preserved…. Of course, a given experimenter may use himself as a ‘subject’ or as an ‘observer’, but he ought properly to treat his own responses and reactions as he would treat those of another observer…. Under this view, the meaning of sensations rests in a set of operations involving an observer, a set of stimuli and a repertoire of responses. Sensations are reactions of organisms to energetic configurations in the environment. The study of sensations becomes a science when we undertake to probe their causes, categorise their occurrences, and quantify their magnitudes.

(Stevens, 1966, p. 218) According to Stevens, such operationalism makes psychological science like physical science. For example,

We know the temperature of a body only through that body’s behaviour which we note by studying the effects the body produces on other systems. It is much the same with sensation; the magnitude of an observer’s sensations may be discovered by a systematic study of what the observer does in a controlled experiment in which he operates on other systems…. He may, for instance, adjust the loudness in his ears to match the apparent intensity of various amplitudes of vibration applied to his fingertips and thereby tell us the relative rates of growth of loudness and the sense of vibration.

(ibid., p. 225—my italics) Or, in the case of visual sensations,

Perhaps the easiest way to elicit the relevant behaviour from an observer is to stimulate his eye, say, with a variety of different light intensities, and to ask him to assign a number proportional to the apparent magnitude of each brightness as he sees it.

(ibid., p. 225—my italics) In terms of methodology, it is clear what such translations of private, subjective states into public, objective measures achieve. Requiring a subject to adjust the growth of loudness in his ears to match the apparent intensity of vibration

applied to his fingertips enables his judgements of heard loudness and felt intensity of vibration to be expressed in terms of the settings of two dials which control the intensity of the auditory and tactile stimuli. This both ‘externalises’ his subjective judgements and expresses them in the form of numbers on two scales.

But the difficulties of removing conscious experiences from psychophysics or of redefining them in this operational way should be clear from Stevens’ inability to describe what subjects are required to do in a way that avoids reference to what they experience. In the auditory/tactile matching task S is required to match the intensity of what he hears to the intensity of what he feels, a procedure which can hardly be said to have removed his experience from the experiment. When quantifying the relative brightness of lights of different intensities, the subject is asked to assign a number proportional to the apparent magnitude of each brightness as he sees it—which makes it difficult to pretend that the subject is doing anything other than reporting on his visual experience (albeit by assigning a number rather than giving a verbal description). Given this, Stevens’ contention that the ‘meaning of sensation rests in a set of operations involving an observer, a set of stimuli and a repertoire of responses’ (i.e. a set of operations that avoids reference to what a subject experiences) seems more an attempt to assimilate the study of sensations to a behaviour ist preconception of psychological science, than an attempt to describe what subjects in perception experiments actually do.

However, that leaves us with a problem. If physical science relies on public, objective data, how can one establish a ‘science of consciousness’ which relies, at least in part, on subjective experiences? Dualists such as Descartes believed this problem to be insoluble (the nature of consciousness, in his view, is a matter for theologians). Reductionists have tried to deal with consciousness by eliminating it or reducing it to something ‘objective’ such as behaviour or a state or function of the brain. Yet neither dualism nor reductionism gives an accurate description of what many subjects and experimenters actually do. In psychological science there are many areas of research which record or try to manipulate subjective exper iences as such, for example in the study of sensation, perception, dreams, imagery, emotion, thinking and so on. In some cases, thousands of experiments have been devoted to the study of just one aspect of these broad research areas. For example, over the period 1887 to 1998, the PsychLit database lists over 3,500 publications on illusions, which are impossible to describe without some reference to what subjects experience. Over the period 1966 to 1998, the Medline database lists over 148,000 publications on pain and its alleviation. That is, pain has been the focus of extensive medical research, in spite of its being a paradigm case of a private, subjective, mental event within philosophy of mind. While there are many ways to measure the subjective experience of pain,3 _{at the present time no} valid ‘objective’ measure of pain experience (in terms of a physiological index) exists.

In sum, modern science does not exclude or eliminate conscious experiences from study, nor does it always replace their study with measures of behaviour or activities in the brain. So, how are we to make sense of this extensive study of private, subjective experiences within a supposedly, public, objective science?4

A closer examination of physical and psychological phenomena

I want to suggest that the problems posed by a ‘science of consciousness’ are largely artefactual, arising from the misconceived dualist splitting of the world into public, objective ‘physical phenomena’ and private, subjective ‘psychological phenomena’ introduced in Chapter 6. This separation of physical phenomena from psychological phenomena is illustrated in a simple way by the separation of physical objects (in the world) from percepts of those objects (in the mind or brain) shown in Figures 6.1 and 6.2.

To see how this works out in a psychophysical experiment, let us replace the cat in Figure 6.1 by a simple stimulus of the kind used in these experiments, such as the light shown in Figure 8.1. Following usual procedures, the subject (S) is asked to focus on the light and report on or respond to what she

Figure 8.1 A dualist model of perception, showing a clear separation between an

‘objective’ stimulus light out in the world (observed by an experimenter) and a ‘subjective’ experience of a light in the mind or brain of the subject.

experiences, while the experimenter (E) controls the stimulus and tries to observe what is going on in the subject’s brain. E has observational access to the stimulus and to S’s brain states, but has no access to what S experiences. In principle, other experimenters can also observe the stimulus and S’s brain states. Consequently, what E has access to is thought of as ‘public’ and ‘objective’. However, E does not have access to S’s experiences, making them ‘private’ and ‘subjective’ and a problem for science, in the ways noted above. This apparently radical difference in the epistemic status of the data accessible to E and S is enshrined in the words commonly used to describe what they perceive. That is, E makes observations, whereas S merely has subjective experiences.

Although this way of looking at things is adequate as a working model for many studies, it actually misdescribes the phenomenology of consciousness— and, consequently misconstrues the problems posed by a science of consciousness. According to the model in Figure 8.2, when S attends to the light in a room she does not have an experience of a light ‘in her head or brain’— with its attendant problems for science. She just sees a light in a room (see

Figure 8.2 A reflexive model of perception, which suggests that in terms of their phenomenology there is no actual difference in the subjective vs. objective status

of the light ‘experienced’ by the subject and the light ‘observed’ by the experimenter.

Chapter 6). Indeed, what the subject experiences is very similar to what the experimenter experiences when he gazes at the light (she just sees the light from a different angle)—in spite of the different terms they use to describe what they perceive (a ‘physical stimulus’ versus a ‘sensation of light’). If so, there can be no actual difference in the subjective versus objective status of the light phenomenology ‘experienced’ by S and ‘observed’ by E. One can easily grasp the essential similarities between S’s ‘experiences’ and E’s ‘observations’ from the fact that the roles of S and E are interchangeable.

A thought-experiment: ‘changing places’

What makes one human being a ‘subject’ and another an ‘experimenter’? Their different roles are defined largely by differences in their interests in the experiment, reflected in differences in what they are required to do. The subject is required to focus only on her own experiences (of the light), which she needs to respond to or report on in an appropriate way. The experimenter is interested primarily in the subject’s experiences, and in how these depend on the light stimulus or brain states that he can ‘observe’.

To exchange roles, S and E merely have to turn their heads, so that E focuses exclusively on the light and describes what he experiences, while S focuses her attention not just on the light (which she now thinks of as a ‘stimulus’) but also on events she can observe in E’s brain, and on E’s reports of what he experiences. In this situation, E becomes the ‘subject’ and S becomes the ‘experimenter’. Following current conventions, S would now be entitled to think of her observations (of the light and E’s brain) as ‘public and objective’ and to regard E’s experiences of the light as ‘private and subjective’.

However, this outcome is absurd, as the phenomenology of the light remains the same, viewed from the perspective of either S or E, whether it is thought of as an ‘observed stimulus’ or an ‘experience’. Nothing has changed in the character of the light that E and S can observe other than the focus of their interest. That is, in terms of phenomenology there is no difference between ‘observed phenomena’ and ‘experiences’.5

This leaves an unanswered question. If the phenomenology of the light remains the same whether it is thought of as a ‘stimulus’ or an ‘experience’, is the phenomenon private and subjective or is it public and objective? These are subtle matters that we need to examine with care.

There is a sense in which all experienced phenomena are private and subjective

In dualism, ‘experiences’ are private and subjective, while ‘physical phenomena’ are public and objective, as noted above. However, according to the reflexive model there is no phenomenal difference between physical phenomena and our experiences of them. When we turn our attention to the external world, physical

phenomena just are what we experience. If so, there is a sense in which physical phenomena are ‘private and subjective’ just like the other things we experience. For example, I cannot experience your phenomenal mountain or your phenomenal tree. I only have access to my own phenomenal mountain and tree. Similarly, I only have access to my own phenomenal light stimulus and my own observations of its physical properties (in terms of meter readings of its intensity, frequency, and so on). That is, we each live in our own private, phenomenal world. Few, I suspect, would disagree.

If we each live in our own pr ivate, phenomenal world, then each ‘observation’ is, in a sense, pr ivate. This was evident to the father of operationalism, the physicist P.W.Bridgman (1936), who concluded that, in the final analysis, ‘science is only my private science’. However, this is clearly not the whole story. When an entity or event is placed beyond the body surface (as the entities and events studied by physics usually are), it can be perceived by any member of the public suitably located in space and time. Under these circumstances such entities or events are ‘public’ in the sense that there is public access to the observed entity or event itself.

Public access to the stimulus itself

This distinction between the phenomena perceived by any given observer and the stimulus entity or event itself is important. Perceived phenomena represent things-themselves, but are not identical to them (see Chapter 7). The light perceived by E and S, for example, can be described in terms of its perceived brightness and colour. But in terms of physics, the stimulus is better described as electromagnetism with a given mix of energies and frequencies. As with all visually obser ved phenomena, the phenomenal light only becomes a phenomenal light once the stimulus interacts with an appropriately structured visual system—and the result of this observed—observer interaction is a light as experienced which is private to the observer in the way described above. However, if the stimulus itself is beyond the body surface and has an independent existence, it remains there to be observed whether it is observed (at a given moment) or not. That is why the stimulus itself is publicly accessible in spite of the fact that each observation/experience of it is private to a given observer.

Public in the sense of similar private experiences

To the extent that observed entities and events are subject to similar perceptual and cognitive processing in different human beings, it is also reasonable to assume a degree of commonality in the way such things are experienced. While each experience remains private, it may be a private experience that others share. For example, unless observers are suffering from red—green colour blindness, we nor mally take it for granted that they

perceive electromagnetic stimuli with wavelength 700 nm as red and those of 500 nm as green. Given the privacy of light phenomenology, there is no way to be certain that others experience ‘red’ and ‘green’ as we do ourselves (the classical problem of ‘other minds’). But in normal life, and in the practice of science, we adopt the working assumption that the same stimulus, observed by similar observers, will produce similar observations or experiences. Thus, while experienced entities and events (phenomena) remain private to each observer, if their perceptual, cognitive and other observing apparatus is similar, we assume that their exper iences (of a g iven stimulus) are similar. Consequently, experienced phenomena may be ‘public’ in the special sense that other observers have similar or shared experiences.

In sum:

• There is only private access to individual observed or experienced phenomena. • There can be public access to the entities and events which serve as the

stimuli for such phenomena (the entities and events which the phenomena represent). This applies, for example, to the entities and events studied by physics.

• If the perceptual, cognitive and other observing apparatus of different observers is similar, we assume that their experiences (of a given stimulus) are