Introduction to The Conscious Mind
Consciousness is the biggest mystery. It may be the largest outstanding obstacle in our quest for a scientific understanding of the universe. The science of physics is not yet complete, but it is well-understood; the science of biology has removed many ancient mysteries surrounding the nature of life. There are gaps in our understanding of these fields, but they do not seem intractable. We have some idea of what a solution to these problems might look like; we just need to get the details right.
Even in the science of the mind, much progress has been made. Recent work in cognitive science and neuroscience is leading us to a better understanding of human behavior and of the processes that drive it. We do not have many detailed theories of cognition, to be sure, but the details cannot be too far off. Consciousness, however, is as perplexing as it ever was. It still seems utterly mysterious that the causation of behavior should be accompanied by a conscious inner life.
We have good reason to believe that consciousness arises from physical systems such as brains, but we have little idea how it arises, or why it exists at all. How could a physical system such as a brain also be an experiencer? Why should there be something it is like to be such a system? Present-day scientific theories hardly touch the really difficult questions about consciousness. We do not just lack a detailed theory; we are entirely in the dark about how consciousness fits into the natural order.
Many books and articles on consciousness have appeared in the last few years, and one might think that we are making progress. But on a closer look, most of this work leaves the hardest problems about consciousness untouched. Often, this work addresses what might be called the "easy" problems of consciousness: How does the brain process environmental stimulation? How does it integrate information? How do we produce reports on internal states? These are important questions, but to answer them is not to solve the hard problem: why is all this processing accompanied by an experienced inner life? Sometimes this question is ignored entirely; sometimes it is put off until another day; and sometimes, it is simply declared answered. But in each case, one is left with the feeling that the central problem remains as puzzling as ever.
This puzzlement is not a cause for despair; rather, it makes the problem of consciousness one of the most exciting intellectual challenges of our time. Because consciousness is both so fundamental and so ill understood, a solution to the problem may profoundly affect our conception on the universe and of ourselves.
I am an optimist about consciousness: I think that we will eventually have a theory of it, and in this book I look for one. But consciousness is not just business as usual: if we are to make progress, the first thing we must do is face up to the things that make the problem so difficult. Then we can move forward toward a theory, without blinkers and with a good idea of the task at hand.
In this book, I do not solve the problem of consciousness once and for all, but I try to rein it in. I try to get clear about what the problems are, I argue that the standard methods of neuroscience and cognitive science do not work in addressing them, and then I try to move forward.
In developing my account of consciousness, I have tried to obey a number of constraints. The first and most important is to take consciousness seriously. The easiest way to develop a "theory" of consciousness is to deny its existence, or to redefine the phenomenon in need of explanation as something it is not. This usually leads to an elegant theory, but the problem does not go away. Throughout this book, I have assumed that consciousness exists, and that to redefine the problem as that of explaining how certain cognitive or behavioral functions are performed is unacceptable. This is what I mean by taking consciousness seriously.
Some say that consciousness is an "illusion", but I have little idea what this could even mean. It seems to me that we are surer of the existence of conscious experience than we are of anything else in the world. I have tried hard at times to convince myself that there is really nothing there, that conscious experience is empty, an illusion. There is something seductive about this notion, which philosophers throughout the ages have exploited, but in the end it is utterly unsatisfying. I find myself absorbed in an orange sensation, and something is going on. There is something that needs explaining, even after we have explained the process of discrimination and action: there is the experience.
True, I cannot prove that there is a further problem, any more than I can prove that consciousness exists. We know about consciousness more directly than we know about anything else, so "proof" is inappropriate. The best I can do is to provide arguments wherever possible, while rebutting arguments from the other side. There is no denying that this involves an appeal to intuition at some point; but all arguments involve intuition somewhere, and I have tried to be clear about the intuitions involved in mine.
This might be seen as a Great Divide in the study of consciousness. If you hold that an answer to "easy" problems explains everything that needs to be explained, then you get one sort of theory; if you hold that there is a further "hard" problem, then you get another. After a point, it is hard to argue across this divide, and discussions are often reduced to table-pounding. To me, it seems obvious that there is something further that needs explaining here; to others, it seems acceptable that there is not. (Informal surveys suggest that the numbers run two or three to one in favor of the former view, with the ratio fairly constant across academics and students in a variety of fields.) We may simply have to learn to live with this basic division.
This book may be of intellectual interest to those who do not think there is much of a problem, but it is really intended for those who feel the problem in their bones. By now, we have a fairly good idea of the sort of theory we get if we assume there is no problem. In this work, I have tried to explore what follows given that there is a problem. The real argument of the book is that if one takes consciousness seriously, the position I lay out is where one should end up.
The second constraint I have followed is to take science seriously. I have not tried to dispute current scientific theories in domains where they have authority. On the other hand, I have not been afraid to go out on a limb in areas where scientists' opinions are as ungrounded as everyone else's. Physics and cognitive science do an excellent job within their own domains, and I have not tried to undermine them. For example, I have not disputed that the physical world is causally closed or that behavior can be explained in physical terms; but if a physicist or a cognitive scientist suggests that consciousness can be explained in physical terms, this is merely a hope ungrounded in current theory, and the question remains open. So I have tried to keep my ideas compatible with contemporary science, but I have not restricted my ideas to what contemporary scientists find fashionable.
The third constraint is that consciousness is taken to be a natural phenomenon, falling under the sway of natural laws. If so, then there should be some correct scientific theory of consciousness, whether or not we can arrive at such a theory. That consciousness is a natural phenomenon seems hard to dispute: it is an extraordinarily salient part of nature, arising throughout the human species and very likely in many others. And we have every reason to believe that natural phenomena are subject to fundamental natural laws; it would be very strange if consciousness were not. This is not to say that the natural laws concerning consciousness will be just like laws in other domains, or even that they will be physical laws. They may be quite different in kind.
The problem of consciousness lies uneasily at the border of science and philosophy. I would say that it is properly a scientific subject matter: it is a natural phenomenon like motion, life, and cognition, and calls out for explanation in the way that these do. But it is not open to investigation by the usual scientific methods. Everyday scientific methodology has trouble getting a grip on it, not least because of the difficulties in observing the phenomenon. Outside the first-person case, data are hard to come by. This is not to say that no external data can be relevant, but we first have to arrive at a coherent philosophical understanding before we can justify the data's relevance. So the problem of consciousness may be a scientific problem that requires philosophical methods of understanding before we can get off the ground.
In this book I reach conclusions that some people may think of as "anti-scientific": I argue that reductive explanation of consciousness is impossible, and I even argue for a form of dualism. But this is just part of the scientific process. Certain sorts of explanation turn out not to work, so we need to embrace other sorts of explanation instead. Everything I say here is compatible with the results of contemporary science; our picture of the natural world is broadened, not overturned. And this broadening allows the possibility of a naturalistic theory of consciousness that might have been impossible without it. It seems to me that to ignore the problems of consciousness would be anti-scientific; it is in the scientific spirit to face up to them directly. To those who suspect that science requires materialism, I ask that you wait and see.
I should note that the conclusions of this work are conclusions, in the strongest sense. Temperamentally, I am strongly inclined toward materialist reductive explanation, and I have no strong spiritual or religious inclinations. For a number of years I hoped for a materialist theory; when I gave up on this hope, it was quite reluctantly. It eventually seemed plain to me that these conclusions were simply forced on anyone who wants to take consciousness seriously. Materialism is a beautiful and compelling view of the world, but to account for consciousness we have to go beyond the resources it provides.
By now, I have grown almost happy with these conclusions. They do not seem to have any fearsome consequences, and they allow a way of thinking and theorizing about consciousness that seems more satisfactory in almost every way. And the expansion in the scientific worldview has had a positive effect, at least for me: it has made the universe seem a more interesting place.
This book has four parts. In the first, I lay out the problems and set up a framework within which they can be addressed. Chapter 1 is an introduction to consciousness, teasing apart a number of different concepts in the vicinity, drawing out the sense in which consciousness is really interesting, and giving a preliminary account of its subtle relation to the rest of the mind. Chapter 2 develops a metaphysical and explanatory framework within which much of the rest of the discussion is cast. What is it for a phenomenon to be reductively explained, or to be physical? This chapter gives an account of these things, centering on the notion of supervenience. I argue that there is good reason to believe that almost everything in the world can be reductively explained; but consciousness may be an exception.
With these preliminaries out of the way, the second part focuses on the irreducibility of consciousness. Chapter 3 argues systematically that standard methods of reductive explanation cannot account for consciousness. I illustrate this conclusion with a critique of various reductive accounts that have been put forward by researchers in neuroscience, cognitive science, and elsewhere. This is not just a negative conclusion: it follows that a theory of consciousness must be a new sort of nonreductive theory instead. Chapter 4 takes things a step further by arguing that materialism is false, and that a form of dualism is true, and outlines the general shape that a nonreductive theory of consciousness might take. Chapter 5 is largely defensive: it considers some apparent problems for my view, involving the relationship between consciousness and our judgments about consciousness, and argues that they pose no fatal difficulties.
In the third part, I try to move toward a positive theory of consciousness. Each of the three chapters here develops a component of a positive theory. Chapter 6 focuses on the "coherence" between consciousness and cognitive processes, drawing a number of systematic links between the two. I use these links to analyze and ground the central role that neuroscience and cognitive science play in explaining human consciousness. Chapter 7 discusses the relation between consciousness and functional organization, using thought-experiments to argue that consciousness is an "organizational invariant": that is, that every system with the right functional organization will have the same sort of conscious experience, no matter what it is made of. Chapter 8 considers what a fundamental theory of consciousness might look like, and suggests that it may involve a close relation between consciousness and information. This is by far the most speculative chapter, but at this point some speculation is probably needed if we are to make progress.
The last two chapters are dessert. Here, I apply what has gone before to central questions in the foundations of artificial intelligence and quantum mechanics. Chapter 9 argues for the thesis of "strong artificial intelligence": that the implementation of an appropriate computer program will give rise to a conscious mind. Chapter 10 considers the baffling question of how quantum mechanics should be interpreted, and uses the ideas about consciousness developed in previous chapters to lend support to a "no-collapse" interpretation of the theory.
Perhaps the negative material will provoke the most reaction, but my real goal is positive: I want to see a theory of consciousness that works. When I first came into philosophy, I was surprised to find that most of the debate over consciousness focused on whether there was a problem or not, or on whether it was physical or not, and that the business of building theories seemed to be left to one side. The only "theories" seemed to be those put forward by those who (by my lights) did not take consciousness seriously. By now, I have come to enjoy the intricacies of the ontological debates as much as anyone, but a detailed theory is still my major goal. If some of the ideas in this book are useful to others in constructing a better theory, the attempt will have been worthwhile.
This book is intended as a serious work of philosophy, but I have tried my best to make this work accessible to nonphilosophers. In my notional audience at all times has been my undergraduate self of ten years ago: I hope I have written a book that he would have appreciated. There are a few sections that are philosophically technical. I have generally marked these with an asterisk, and readers should feel free to skip them. The most technical material is in Chapter 2 and Chapter 4. Section 4 of the former and sections 2 and 3 of the latter involve intricate issues in philosophical semantics, as does the final section of Chapter 5. Other asterisked sections might be worth at least skimming, to get an idea of what is going on. Often, I have put especially technical material and comments on the philosophical literature in the endnotes. The one technical concept that is crucial to the book is that of supervenience, introduced in at the start of Chapter 2. This concept has an intimidating name but it expresses a very natural idea, and a good understanding of it will help central issues fall into place. Much of the material in this chapter can be skipped on a first reading, although one might want to return to it later to clarify questions as they arise.
For a short tour that avoids technicalities, read Chapter 1, skim the early parts of Chapter 2 as background material, then read all of Chapter 3 (skimming section 1 where necessary) for the central arguments against reductive explanation, and the first and last sections of Chapter 4 for the central considerations about dualism. The beginning of Chapter 6 is worth reading for the basic shape of the positive approach. Of the positive material, Chapter 7 is perhaps the most self-contained chapter as well as the most fun, with easy-to-understand thought-experiments involving silicon brains; and those who like wild and woolly speculation might enjoy Chapter 8. Finally, Chapters 9 and 10 should make sense to anyone with an interest in the issues involved.
A couple of philosophical notes. The philosophical literature on consciousness is quite unsystematic, with seemingly independent strands talking about related issues without making contact with each other. I have attempted to impose some structure on the sprawl by providing a unifying framework in which the various metaphysical and explanatory issues become clear. Much of the discussion in the literature can be translated into this framework without loss, and I hope the structure imposed by the framework brings out the deep relationships between a number of different issues.
This work is perhaps unusual in largely eschewing the notion of identity (between mental and physical states, say) in favor of the notion of supervenience. I find that discussions framed in terms of identity generally throw more confusion than light onto the key issues, and often allow the central difficulties to be evaded. By contrast, supervenience seems to provide an ideal framework within which the key issues can be addressed. To avoid loose philosophy, however, we need to focus on the strength of the supervenience connection: Is it underwritten by logical necessity, natural necessity, or something else? It is widely agreed that consciousness supervenes on the physical in some sense; the real question is how tight the connection is. Modality is the key issue here. Discussions that ignore this issue generally avoid the hardest questions about consciousness. Those skeptical of modal notions will be skeptical of my entire discussion, but I think there is no other satisfactory way to frame the issues.
One of the delights of working on this book, for me, has come from the way the problem of consciousness has reached out to make contact with deep issues in many other areas of science and philosophy. But the scope and depth of the problem also make it humbling. I am acutely aware that at almost every point in this book there is more that could be said, and that in many places I have only scratched the surface. But I hope, minimally, to have suggested that it is possible to make progress on the problem of consciousness without denying its existence or reducing it to something it is not. The problem is fascinating, and the future is exciting.