A Universe Of Consciousness

PART ONE
The World Knot

With this simple example, in 1940, the great neurophysiologist Charles Sherrington illustrated the problem of consciousness and his belief that it was scientifically inexplicable.

A few years earlier, Bertrand Russell used a similar example to express his skepticism about the ability of philosophers to arrive at a solution:

No matter how accurate the description of the physical processes underlying it, it is hard to conceive how the world of subjective experience—the seeing of blue and the feeling of warmth—springs out of mere physical events. And yet, in an age in which brain imaging, general anesthesia, and neurosurgery are becoming commonplace, we are aware that the world of conscious experience depends all too closely on the delicate workings of the brain. We are aware that consciousness, in all its glory, can be annihilated by a minuscule lesion or a slight chemical imbalance in certain parts of the brain. In fact, our conscious life is annihilated every time the mode of activity in our brain changes and we fall into dreamless sleep. We are also aware that our own private consciousness is, in a profound sense, all there is. The flattened dome of the sky and the hundred other visible things underneath, including the brain itself—in short, the entire world—exist, for each of us, only as part of our consciousness, and they perish with it. This enigma wrapped within a mystery of how subjective experience relates to certain objectively describable events is what Arthur Schopenhauer brilliantly called the “world knot.”³ Despite the appearance of mystery, the best hope of disentangling this knot will come from a scientific approach that combines testable theories and well-designed experiments. This book is dedicated to this end.

CHAPTER ONE

Consciousness: Philosophical Paradox or Scientific Object?

The subject of consciousness has not lacked for human attention. In the past, it was the exclusive domain of philosophers, but recently both psychologists and neuroscientists have begun to attack the so-called mind-body problem or, in Schopenhauer’s suggestive phrase, “the world knot.” In this chapter we briefly review classical and modern approaches to consciousness. We point out various positions taken by philosophers, psychologists, and neuroscientists, rejecting some of the more flagrant ones, such as dualism or extreme reductionism. We suggest that consciousness can be considered a scientific subject and that it is not the sole province of philosophers.

Everyone knows what consciousness is: It is what abandons you every evening when you fall asleep and reappears the next morning when you wake up. This deceptive simplicity reminds us of what William James said of attention at the turn of the century: “Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.”¹ More than one hundred years later, many think that neither attention nor consciousness is understood in any fundamental sense.

This lack of understanding is certainly not because of lack of attention in philosophical or scientific circles. Ever since René Descartes, few subjects have preoccupied philosophers so consistently as the riddle of consciousness. For Descartes, as for James more than two centuries later, to be conscious was synonymous with “to think”: James’s stream of thought, for example, was nothing but the stream of consciousness. The cogito ergo sum, “I think therefore I am,” which Descartes posed as the foundation of his philosophy in his Meditationes de Prima Philosophia,² was a direct recognition of the centrality of consciousness with respect to both ontology (what is) and epistemology (what and how we know).

If taken too seriously, “I am conscious, therefore I exist” can lead to solipsism, the view that nothing exists but one’s individual consciousness, evidently not a view that can appeal to two authors who are sharing the writing of a book. More realistically (pun intended), that starting point leads to idealistic positions that emphasize mind over matter—ideas; perception; thought; or, in one word, consciousness. By taking mind as a starting point, however, idealistic philosophies must take pains to explain matter—which is not necessarily a better predicament than starting from mere matter to derive mind.

Descartes argued that there is an absolute distinction between mental and material substance. The defining characteristic of matter, he thought, is to be extended, to occupy space, and thus be susceptible to physical explanation, whereas the defining characteristic of mind is to be conscious or, in a broad sense of the term, to think. In this view, mental substance exists in the form of individual minds. In this way, Descartes inaugurated dualism, a position that is unsatisfactory scientifically but appears intuitively simple and appealing until one attempts to explain the connection between the mind and the body (see figure 1.1). Since the days of Descartes, philosophers have suggested versions of dualism or related alternatives. For example, a related theory is epiphenomenalism, which agrees with other theories in holding that mental events and physical events are different but maintains that the only true causes of mental experiences are physical events, with mind as a causally inefficacious by-product. In the words of Thomas Huxley, “consciousness would appear to be related to the mechanism of [the] body simply as a collateral product of its working, and to be as completely without any power of modifying that working as the steam whistle that accompanies the working of a locomotive engine is without influence upon its machinery.”³

In more recent times, philosophers have taken a materialistic stance, holding that the mind and consciousness are identical to the operations of the brain or, at least, to certain of these operations. Some materialistic positions go so far as to deny any ontological or epistemic validity to conscious- ness; they insist that there is literally nothing else beyond the functioning of brain circuits or, at least, that there is nothing else that needs to be explained. Several philosophers have suggested that once we understand the workings of the brain sufficiently well, the concept of consciousness will evaporate just as the concept of phlogiston (a hypothetical volatile constituent of all combustible substances that was thought to be released as a flame in combustion) evaporated when oxidation was understood. The mind-body problem is thus made to disappear by denying or explaining away the consciousness side of it. Other materialistic positions insist that although consciousness is generated by physical events in the brain, it is not reduced to them but, rather, emerges from them, just as the properties of water emerge from the chemical combination of two hydrogens and one oxygen but are not directly reducible to the properties of hydrogen or oxygen alone. Such positions come in various flavors, but, in general, they grant consciousness some residual status, at least from the point of view of explanation. Nevertheless, they insist that there is no “consciousness” substance separate from a “brain” substance.

The philosophical debate on the mind-body problem is by now extremely sophisticated and, in their variety, some current disputes rival those that flourished among post-Cartesian philosophers. As we had Spinoza’s dual-aspect theory, Malebranche’s occasionalism, Leibniz’s parallelism and his doctrine of preestablished harmony, we now have the identity theory, the central state theory, neutral monism, logical behaviorism, token physicalism and type physicalism, token epiphenomenalism and type epiphenomenalism, anomalous monism, emergent materialism, eliminative materialism, various brands of functionalism, and many others.⁴

Despite the profusion of philosophical positions, it appears unlikely that philosophical arguments alone will lead to a satisfactory solution to the mind-body problem. In the words of Colin McGinn,⁵ a philosopher who takes an extreme position: “We have been trying for a long time to solve the mind-body problem. It has stubbornly resisted our best efforts. The mystery persists. I think the time has come to admit candidly that we cannot solve the mystery. [We still have no idea of how] the water of the physical brain is turned into the wine of consciousness.”

There is indeed a fundamental limitation on philosophical efforts to discern the origins of consciousness that arises, in part, from the presumption that the sources of conscious thought can be revealed by thinking alone. This presumption is as patently inadequate as efforts in previous times to understand cosmogony, the basis of life, and the fine structure of matter in the absence of scientific observations and experiments. In fact, philosophers have excelled not so much in proposing solutions to the problem but in pointing out just how intractable the problem is. What many philosophers are reiterating amounts to this: No matter what scientists do, the first-person and third-person perspectives of conscious individuals will not be reconciled, the explanatory gap will not be bridged, and the “hard” problem—the generation of sensations, of phenomenal or experiential states out of the buzzing of neurons—will not be solved.⁶

How have scientists fared in explaining the mystery? If we look at psychology, we find that the “science of the mind” always had trouble in accommodating what should be its central topic—consciousness—within an acceptable theoretical framework. The introspectionist tradition of Titchener and Külpe⁷ was the psychological counterpart of idealistic or phenomenological positions in philosophy; it attempted to describe consciousness viewed by the individual exclusively from the inside, hence the term introspection. Many introspectionists were psychological atomists; not unlike some present-day neurophysiologists, they postulated that consciousness was made up of elementary parts that could be catalogued (never mind that the American school came up with more than 40,000 sensations and the German school with just 12,000). By contrast, behaviorists notoriously attempted to eliminate consciousness completely from scientific discourse, a position not unlike that of some contemporary philosophers.