Consciousness is a multifaceted phenomenon, and many terms are used to describe its facets. Consciousness, conscious, aware of, experience (noun), and experience (verb)— all these words have different meanings in different contexts and for different people, so generalizations about their meaning will necessarily have limited validity. Considerable discrepancies also exist between the conceptual tools available in different languages for classifying consciousness and related phenomena. So, for example, the French conscience encompasses both "consciousness" and "conscience," as the latter words are used in English; in German the subtle difference between the meanings of the English words "consciousness" and "awareness" is lost when both these words have to be translated as Bewusstsein.
BASIC DEFINITIONS AND PHILOSOPHICAL ISSUES
Because of these linguistic and conceptual problems, every systematic treatment of consciousness has to start with a set of distinctions and definitions for the purpose at hand. The task of formulating these in a way that makes them useful for people with different mother tongues is far from simple. However, aspects of consciousness and related phenomena can be classified in three basic categories: cognitive consciousness, phenomenal consciousness, and control consciousness. All are the subject of ongoing philosophical debates.
Cognitive Consciousness Also referred to as intentionality, consciousness-of awareness-of and transitive consciousness, cognitive consciousness entails a mental relation to an object (not necessarily an existing one), and encompasses phenomena such as thinking of a dragon, becoming aware of the presence of another person, attending to a problem and knowing facts about a certain field. In English, awareness is often a more natural choice than consciousness when the cognitive aspect of consciousness is intended. However, the term "consciousness" is not seldom used in an exclusively cognitive sense—for example, the sociological and political terms class consciousness, gender consciousness, and environmental consciousness. Here consciousness stands for habitual attention to, and knowledge about, the issues in question.
The common denominator of all cognitive consciousness is its directedness toward an object, which may be concrete or abstract. It is an important conceptual fact that a person can properly be said to be cognitively conscious although she is in another sense (phenomenal consciousness, as discussed below) not conscious at all. For example, an environmentally conscious person is still environmentally conscious when sleeping dreamlessly. Similarly, since a person in dreamless sleep knows her mathematics, she is cognitively aware of mathematical facts while sleeping. On the other hand, there are forms of cognitive consciousness that cannot plausibly be ascribed to a dreamlessly sleeping subject, for example, thinking of or presently attending to the facts that she knows.
In this context it should also be mentioned that self-consciousness, which is not seldom given a fundamental role in conceptual schemes for handling matters of consciousness, can plausibly be argued to be a species of cognitive awareness (namely, of oneself). The same holds for reflexive consciousness.
Phenomenal Consciousness A good alternative term is experiential consciousness ; sentient consciousness is often given a similar sense but can also have other connotations. A dreamless sleeper does not have any present experiences (or we may suppose so for the sake of this discussion), and is therefore not conscious in the phenomenal sense. An awake person, on the contrary, usually has sensory and perceptual experiences, feels emotions, and entertains mental imagery; all these belong to her phenomenal consciousness.
Two long-standing controversies in philosophy of mind primarily concern phenomenal consciousness: the mind-body problem and the problem of other minds. What is the relation between the brain and phenomenal consciousness? The philosopher David Chalmers (1996) has called this "the hard problem of consciousness." The problem of other minds is, can we ever know what another person’s, or another animal’s, experiences are like?
The relations between cognitive awareness and phenomenal consciousness have been the topic of many philosophical debates. One classic debate concerns whether cognition is necessarily rooted in phenomenal consciousness, or whether one could give an explanation of it in purely nonphenomenal (for example, physical) terms. Philosophers in the so-called phenomenological school argue for the first position, whereas most present-day analytical philosophers and cognitive scientists, not only those of a strictly materialist bent, defend the second.
Today this discussion is usually presented as an issue about the nature of mental representations. Another important controversy concerns whether phenomenal consciousness depends on cognition: Is a pain or a thought phenomenally conscious only by virtue of one’s being conscious of it, or is phenomenal consciousness rather an intrinsic quality of experiences that can be possessed independently of any reflexive consciousness?
Control Consciousness The meaning of this term, for which there are no common synonyms, partly overlaps with that of what Ned Block (1994) calls access consciousness. In our commonsense understanding of ourselves and other people, as well as in many psychological, psychiatric, and neuroscientific theories, consciousness is given a role for initiating and/or controlling behavior. We talk about doing things with or without conscious intention. Psychologists and neurophysiologists speak about automatic versus consciously controlled behavior. A good example of the latter distinction is given by our ordinary, unconscious control of bodily posture versus conscious attempts not to fall when the automatic control fails for some internal or external reason. In some psychiatric theories, consciousness is even given the role of the super-ordinate controlling instance of mental life, and all mental disturbances are seen as results of more or less deep-seated disturbances of consciousness.
A philosophically controversial issue here is: How can consciousness have a causal role to play in behavior, if all our behavior stems from processes in the brain (as neuro-science seems to say)? This problem is sometimes taken as a motive for a materialistically reductive analysis of control consciousness. Control consciousness is then explained in terms of physical or biological regulatory processes. However, such an approach also has to explain the fact that many paradigm cases of conscious control (e.g., consciously regaining posture) also have a phenomenal aspect.
HISTORICAL CONCEPTIONS OF CONSCIOUSNESS
The French philosopher and mathematician Rene Descartes (1596-1650) formulated a philosophical conception of consciousness in which the concept was differentiated from conscience, with which it was previously conflated. Descartes’s dualism is well known, and already in the seventeenth century it posed an embarrassing philosophical issue, the body-mind problem. He regarded body and mind as two separate but interacting substances, body (or matter) being essentially characterized by spatial extension whereas mind is characterized by thinking. For Descartes the presence of conscious states was a mark of human beings, in contrast with animals, which he thought were mechanical automata.
Although a clear emphasis on cognitive consciousness can be discerned in Descartes’s writings, the cognitive, phenomenal, and control dimensions of consciousness cannot really be disentangled in them. In seventeen th-and eighteenth-century British empiricist philosophy, phenomenally conscious processes and our consciousness of them are the main concerns. However, the problems of cognitive consciousness are still of central concern. For the British empiricists, ideas are experiential states that are accessible by means of introspection, but they are also themselves essentially about things.
John Locke (1632-1704) formulated the distinction between an outer sense—our experiential access to material objects—and an inner sense, reflecting on one’s own experiences. His theory of inner sense can be regarded as the first systematic treatise of introspection. By consciousness Locke meant all ideas that passed in a man’s own mind and his self-consciousness about them. Consciousness, not bodily continuity, was regarded as constitutive of personal identity.
The famous principle of association of ideas can be traced to Aristotle, but it was the British empiricists who made it the foundation of a whole new science. Locke’s formulation of the principle became of utmost importance for the development of psychological ideas in later centuries. Our understanding of the world and of ourselves was seen as built up from associations between ideas that are similar or contrasting, or that just happen to be contiguous in our experience. Later schools of association-ist philosophy and psychology (as exhibited in the work of David Hartley, David Hume, James Mill, John Stuart Mill, and Alexander Bain) took it for granted that conscious experience is built up from elements and processes that are discernible to the self-conscious mind. Simple ideas are copies of sensations, and complex ideas are construed from simple ideas according to the laws of association. Mental elements and the principles according to which conscious thoughts—or ideas—are built up and interact can be investigated by introspection.
In the late eighteenth century the German philosopher Immanuel Kant (1724-1804) questioned the program of the British associationist philosopher-psychologists. According to Kant, a science in the strict sense requires both mathematical measurement and experimental procedures. None of this is possible in the case of consciousness, as thoughts do not exist in a spatial continuum and as man cannot divide himself into one observing subject and one observed object.
THE BIRTH OF EXPERIMENTAL PSYCHOLOGY
Trying to overcome the obstacles put up by Kant, German philosophers in the nineteenth century formulated several programs for a science of psychology defined as the study of conscious processes. Based on the psychophysical methods the physicist Gustav Theodor Fechner (1801-1887) had devised in 1860, the German physiologist and philosopher Wilhelm Wundt (1832-1920) institutionalized the new science in Leipzig in 1879 as an experimental laboratory discipline. Wundt and his students defined psychology as the study of immediate experience. They held that it was a proper scientific discipline and that mental processes can be measured provided that one uses controlled experimental methods. Simple introspection was therefore replaced by experimental self-observation, a method that required a painstaking training before the subject could correctly describe the phenomena in his consciousness.
In his Principles of Psychology (1890), the American physician and philosopher William James (1842-1910) described psychology as "the science of mental life." He tried to give a holistic description of consciousness, stressing consciousness as personal, intentional, selective, shifting, and continuous. James’s discussion of consciousness as "a stream of thought" is very similar to the understanding of consciousness in the theories of Franz Brentano, Carl Stumpf, and Edmund von Husserl. During the late nineteenth and early twentieth centuries, the latter philosophers developed what Husserl (1859-1938) in his 1900-1901 work named phenomenology. Phenomenology is a philosophy that emphasizes the intentionality of consciousness and the importance of investigating the detailed intentional structure of consciousness. This should be done by means of a certain method, which, although systematically related to introspection, is not identical to it.
In opposition to the British associationists, the phenomenologists stressed the fact that conscious ideas need not be similar to that which they are ideas of. In other words, it is not essential to ideas that they are images of their objects. At the beginning of the twentieth century, the psychologists of the so-called Wurzburg school (Narziss Ach, Karl Buhler, Oswald Kulpe, and others) took an interest in deeper descriptions of phenomena of consciousness. They found in the experimental subjects’ introspective reports instances of "imageless" conscious phenomena (Bewusstseinslagen) that in their opinion questioned the traditional associationist psychology.
BIOLOGICAL, FUNCTIONALISTIC, AND BEHAVIORIST PERSPECTIVES
During the late nineteenth century there was widespread interest in the possibility of unconscious mental phenomena. Sigmund Freud (1856-1939) famously formulated a systematic theory, or rather several theories, about the unconscious mind. Such an enterprise requires a theory of consciousness. In a crucial paper written in 1915, Freud distinguishes between a "systematic" and a "descriptive" sense of "consciousness." The systematic sense is close to what is here called control consciousness. The descriptive sense has essentially to do with knowability, but Freud also speculates that a descriptively conscious mental state is conscious by virtue of its possessing a certain intrinsic quality. In Freud’s later thinking, control consciousness is instead described in terms of the mental systems named ego and super-ego.
Within the American school of functionalism that William James was part of, the aim of studying consciousness was regarded with suspicion. In 1904 James even stated that consciousness did not exist, but he meant that it did not exist as an entity, only as a function. With the behaviorists of the early twentieth century, however, the interest radically shifted from consciousness (now often regarded as a metaphysical concept) to behavior. Humans should be understood through their actions and not their thoughts. The idea of finding the basic laws of mental elements using introspective methods was abandoned. The alternative, nonassociationist approaches, such as phenomenology and Gestalt psychology, were also relegated to a minor role in the psychological community. The behaviorists took diverse philosophical positions: Some took the strong metaphysical position that consciousness does not exist, whereas others only defended a moderate methodological statement to the effect that introspective methods should be abandoned as unscientific in favor of behavioral observation.
Behaviorism was to dominate the behavioral and social sciences from about 1920 to 1960. During this time the Gestalt psychologists, who thought in ways related to both phenomenology and the Wurzburg school, kept up a keen interest in the study of perception and other forms of experience and did much valuable research on the structure of consciousness. In many respects the thrust of their work was biological, and they were much opposed to explanations of experience by means of mental laws. In Gestalt theory, immediate experience is a direct result of brain processes and cannot be explained by any association of mental elements.
Consciousness research continued throughout the behaviorist era in the fields of psychiatry and neurology. Karl Jaspers (1883-1969), a psychiatrist and philosopher in the phenomenological tradition, in 1913 created a classification scheme for pathological disturbances of consciousness that is still in use. During the whole of the twentieth century, the understanding of consciousness and its pathology was generally regarded as essential for the psychiatric understanding of patients. Around mid-century, the French psychiatrist Henri Ey (1900-1977)— who was also influenced by phenomenological thinking—formulated a new theory about consciousness, stressing its functional and controlling aspects. In most present-day psychiatric theories, however, consciousness is not given such a central explanatory role.
The Cognitive Revolution In the 1960s an important methodological and theoretical shift in the behavioral and social sciences occurred that is often referred to as the cognitive revolution. It was partly inspired by the possibilities offered by computer modeling of rational processes, and it is no coincidence that the main focus of cognitive psychology is memory and thinking. Consciousness was no longer a forbidden territory. Since the 1960s, cognitive psychologists have also shown a renewed interest in unconscious mental processes such as implicit memory, subliminal perception, and other forms of perception without phenomenal perceptual consciousness (e.g., blindsight).
Although consciousness and several different kinds of introspective procedures have once again been admitted into psychology, the terms introspection and consciousness are not used as frequently by psychologists as they were in the early twentieth century. This may not be of any importance in itself, but it reflects the more serious circumstance that there is a fundamental break of tradition between the old psychology and the new. This break also means that several philosophical and methodological issues, which were common knowledge in the psychological community in the early 1900s, seem to be little known by many behavioral and social scientists of the twenty-first century.
However, there are signs that this situation is changing. Since the 1990s a large amount of interdisciplinary work on consciousness has been accomplished, partly under the auspices of independent organizations such as ASSC (Association for the Scientific Study of Consciousness), but also within the academic programs of many universities around the world. Neuroscientists and philosophers, as well as behavioral and social scientists, participate in this effort. The body-mind problem occupies one focus under the name of a search for "the neural correlate of consciousness." The role of consciousness in perceptual and motor processes is another much researched and hotly debated topic. Finally, "mentalizing" (ascribing mental states to other people) is a third area of central concern for today’s interdisciplinary study of consciousness.
