If you haven't read Section 1, you may like to read that first:
The idea that matter is the ultimate reality has been the mainstay of modern science. The great strength of this view is that it cuts radically through all forms of religious hypocrisy, dogmatism and superstition. As a collective enterprise, it appears to have contributed to our incredibly detailed and fast-increasing knowledge of the physical domain. There is an ontological and an epistemological side to it.
At its extreme, ontological physicalism holds that the physical reality is all that exists. As mentioned earlier, the great difficulty for ontological physicalism is how to account for experience, love, truth, beauty, ideas and all those other things that do not appear to be physical in any ordinary sense of the word. Much of this non-physical stuff is in some way or another related to the subjectivity of consciousness, and physicalists tend to have a serious problem with subjectivity as well as with consciousness. Watson, the father of behaviourism, bundles everything not directly physical away as "the trouble". Skinner, who according to many is one of the greatest psychologists of the twentieth century, claims it is "functionally irrelevant"5. And David Chalmers, one of the founding fathers the Consciousness Studies movement, calls the way consciousness arises out of matter "the hard problem"(1995) . Only few amongst the adherents to this theory bother to write about consciousness, and when they do, they have different ways of explaining its (apparent) presence. There are two main groups. The first claims that mind and consciousness are nothing more than chemical reactions in the working brain. Daniel Dennet, for example, says that we are our neurons and Patricia Churchland compares consciousness to heat, which, at least in her eyes, is nothing beyond the kinetic energy of moving molecules. The second group claims that consciousness is a different, higher order phenomenon that "emerges" out of material reality at a certain level of physical complexity. John R. Searle compares it to fluidity, which does not exist in a single water molecule but comes into being when you put enough of them together. On both sides, the majority takes it for granted that the brain "causes" consciousness, in the strong, exclusive sense that you cannot have consciousness unless you have a working brain (or at least a physically existing functional equivalent of a brain). There are many different positions within this camp, but there is none that has not come under attack by the others. Churchland and Dennet have been accused of explaining consciousness away, and Searle stands accused by Dennett of confusing subjective illusion with objective reality.
Though ontological physicalism is philosophically hard to defend since it denies or trivialises everything that really matters to people,6 the physicalist concept of consciousness is unlikely to disappear anytime soon. The reason is that it is so eminently useful in medical practice, and especially in emergency care: if a person is "unconscious" there is an increased likelihood that the brain is physically damaged or the brain-chemistry is seriously off balance, and immediate specialist attention may be required. Moreover, a number of tasks that are otherwise taken care of by the patient, like providing information and making decisions about treatment, will have to be taken over by others. Even in less life-threatening situations, medical professionals are confronted on a daily basis with the fact that even small changes in blood chemistry or minor damage to the physical brain tend to have a dramatic effect on a person's consciousness. The opposite, situations where the consciousness seems to operate normally in spite of a seriously impaired brain-function are far more rare; they are moreover often somewhat subtle and easy to miss. Though there is an increasing interest in them, there is still a widespread tendency to dismiss them as anomalous or freak phenomena for which science will find a "proper" physical explanation in due time.
Epistemological physicalism does not bother about deep metaphysical questions regarding the essential nature of reality, but argues that, whatever the world may be made of, the physical reality is all that we can know scientifically. Within psychology, classical behaviourism comes closest to this view: It looks at the human mind as a black box, about which nothing can be known, or needs to be known, as long as one knows the rules that connect purely physical input (the stimulus) to purely physical output (the response). As we have seen in the chapter "What is Psychology", the serious difficulties with this view have become more and more apparent. It does not work in the simple, pragmatic sense that knowing the stimuli a person receives does not reliably predict his response except in the most trivial of laboratory situations. It is third-person and thus intrinsically manipulative. And it is not really impartial because of the degree to which the researcher's questions and observations are determined by social, cultural and political influences. In spite of all this, classical behaviourism reigned in psychology for over 40 years. Since then psychology has widened its horizon considerably, but physicalist influences are still far more pervasive than those within the system seem to realize.7
In mainstream psychology, consciousness and the inner states and processes that take place within it are hardly ever studied directly. In order to allow the researcher to remain objective, almost all psychological research consists at present of sophisticated statistical analysis of unsophisticated self-observations by representative members of the general public. This arrangement allows the scientist to deal in an objective manner with subjective issues, but he can do so because he has outsourced the crucial job of exploring the subjective inner realities to the public. Research about more rare spiritual experiences tends to be booked under cross-cultural, religious or spiritual studies which focus on the cultures that support them or the scriptures in which they have been described, but not on the inner reality that these experiences refer to. Here too the researcher stays objective by inserting a layer that can be studied objectively between himself and the subjective reality he is supposed to be studying. Whether he creates a "quantitative" statistical surveys or a "qualitative" description of what others say about themselves, he can not progress much beyond what his subjects already know, and it is hard to see how such research could ever lead to the kind of cumulative progress we see in the hard sciences.
For the issue-wise comparison in the next Section, I will focus on the physicalist position as it is used in medicine. It is anthropocentric in the sense that it limits consciousness to the type of consciousness we humans have in our ordinary waking state, and it takes it for granted that consciousness is produced by the brain, but beyond this it does not deny or trivialise consciousness. In science, this position deserves to be called mainstream not only because it plays such a crucial role in the day-to-day practice of medicine, but also because it informs almost all neurological and psychological research. Even those authors who have a different position still tend to take it as the "given view" from which they subsequently differentiate their own standpoint. And finally, it is a view that is based on common experiences and lines of thought that everybody can understand. In contemporary Consciousness Studies, the most prominent protagonist of this view is probably John R. Searle.
For the exclusive spiritual concept of consciousness:
6. One might object that in the end, food, health and survival are more important to people than the relative luxuries of beauty, love, meaning etc, but without consciousness, even food, health and survival would not exist for us.
7. Strangely this is true even for research following the constructionist paradigm, which, in theory, is ontology independent: in practice, the majority of those working in the constructionist field also tend to take the physicalist view of reality for granted.