Consciousness

The middle of the twentieth century witnessed a decline in discussion of consciousness. The research programs associated with the chief intellectual trends of the time had no fruitful implications for our understanding of consciousness: Martin Heidegger (1889–1976) directed phenomenology toward ontology and hermeneutics; structuralism and poststructuralism studied texts and languages; Marxism considered subjective consciousness to be derived from the more basic and objective material relations of production; in psychology, behaviorism ignored consciousness, while in philosophy logical positivism ignored in principle what cannot have immediate operational, empirical, effects. Behaviorism and positivism, the dominant schools respectively in academic psychology and philosophy until the sixties, ignored the study of consciousness because it could not be reduced to observable behavior or empirically verified. Since the study of private consciousness was beyond the methods associated with the research programs of either school, it was left to literature and mysticism.

In the last few decades of the twentieth century several intellectual developments led to refocusing of philosophy, especially in English-speaking countries, on the problem of consciousness. The failure of philosophical positivism to explain actual scientific theories that contain nonobservable concepts such as energy, and the uselessness of behaviorism for the solution of many problems in psychology in comparison with alternative research programs, spurred an academic search for more fruitful research programs and a return to the problem of consciousness.

Advances in neurology; the physical study of the brain, using brain scanning, rare cases of localized brain damage, and so forth; the discovery of genetic causes for a variety of mental illnesses; and research into the effects of drugs on the brain allowed scientists for the first time to offer physiological, material explanations to a variety of states of consciousness. At the same time, advances in computer technology generated advanced forms of artificial intelligence. For the first time, humans created artifacts that appeared more intelligent than themselves. This led to a reexamination of popular conceptions of the distinctive essence of humanity. If not intelligence, perhaps consciousness could distinguish us from our machines?

Philosophers, scientists, and writers wondered about the prospects for conscious artificial intelligence, and hence about the meaning of consciousness. The knowledge acquired about complex information processing through the analysis of systems, such as those of artificial intelligence, prepared expectations for attempting to understand the mind as a complex information-processing system, and consciousness in those terms. These developments have led to the founding of the new, yet controversial, "cognitive science"—"cognitive silence" for its detractors.

The discussion of consciousness in recent philosophy of mind may be traced to Thomas Nagel's (1974) groundbreaking reformulation of the mind-body problem, the relation between the physical and the mental. Nagel asked whether the physical-material external description of brain states could ever explain the mental internal experience of consciousness. Nagel argued that there is and always will be an "explanatory gap" between our consciousnesses and what a science of the mind may explain, however sophisticated it becomes. It will never be able to explain "what it is like" to have specific points of view, for example, what it is like to be a bat, hang upside down from the ceiling, and sense radar rays.

Much of the subsequent debate centered on reasons for affirming or denying the existence of the explanatory gap. Dualists like Nagel and John Searle suggested that though consciousness is a natural phenomenon, we lack the concepts and theories to close the explanatory gap. Eliminativism claims that there is no explanatory gap because consciousness does not exist; it "eliminates" the explanatory gap by eliminating consciousness. Daniel C. Dennett (1991), following Julian Jaynes (1976), claimed that consciousness is a cultural construct that emerged in ancient Greece.

Functionalists such as Australian philosopher D. M. Armstrong and Hilary Putnam proposed to characterize states of consciousness by their causes and effects, rather than by their internal properties. Physicalists claim that ultimate reality is material and described by physics. Both consider the explanatory gap as a problem of reduction of the mental to the physical. They recognize that there is at present an explanatory gap, but they believe that it may be possible to close it through a successful scientific reduction of the mental to physical theories. Some advocated that such a reduction will prove that a type of conscious state such as being in love or seeing red will be reduced to a physical or chemical description of a brain state. Others, such as Patricia and Paul Churchland, envisioned the reduction of what they call "folk psychology" to an advanced neuroscience along the lines of the reduction by chemical theories of ordinary descriptions of chemical interactions to a small number of types of basic elements and the laws that govern their interactions. Such a reduction may demonstrate correspondence between several types of physical interaction and the same conscious state, as the same tune may be played by a variety of different orchestral arrangements.

Frank Jackson (1982) and David Chalmers (1996) argued that scientific material external explanations cannot explain consciousness, since it is possible to conceive of a universe where the descriptions of material states of affairs that explain consciousness are true, but people do not develop consciousness, a world of zombies that act in response to stimuli without being conscious. For example, people may react to hunger by eating and to danger by defending themselves without being conscious of dining or fighting. Such a problem does not exist when scientists reduce water to two atoms of hydrogen and one atom of oxygen. Colin McGinn (1991) went further by suggesting that human beings are forever blocked from knowing the link between physical brain states and consciousness because introspective consciousness provides no immediate knowledge of brains, while neuroscientific knowledge of brains provides no access to consciousness.

Frank Jackson (1982) further attacked physicalism by demonstrating that some qualia, the subjective qualities of conscious experience, cannot be reduced to physical facts. Jackson introduced the following thought experiment: Suppose that a scientist named Mary was locked all her life in a room where everything was in black and white but had access to the world outside through black and white books and television. Mary could learn everything that science can teach us about colors, optics, and wavelengths, how they interact with the eye and transmitted to the brain, and so forth. Still, though Mary would be familiar with the physicalist-scientific explanation of color, it would not prepare her for anything like the actual experience of red, because it is irreducible to scientific physical descriptions.

Physicalist responses to Jackson's thought experiment claimed that Mary's new experience of red would not add to the number of facts she knows, rather it would represent knowledge of old facts in a new way, or a broadening of Mary's imagination. The description and explanation of mental causation of physical effects is a major problem for dualists like Jackson. Eliminativists do not think there is consciousness, only perceptions of it, no qualia, properties of experience, but perceptions of qualia "as if" there were mental objects. So, mental causation of physical events is not a problem for them because they deny the mental. Jackson advocated epiphenomenalism; he considers consciousness to be a side effect of physical processes that connects physical causes with effects. Consciousness is irrelevant for the generation of physical events. Consciousness emerges then from physical interactions, has properties that are irreducible to those of a physical lower level, and so is more than the sum of its parts. A related question is whether the emergence of consciousness may be explained by Darwinian evolution as conveying some sort of adaptationist advantage.