What is consciousness? What does it do? Could we have evolved without it? ‘Why the mystery?’ considers the definition of consciousness and how psychologists, neuroscientists, and philosophers have tried to explain it. From the Cartesian dualism of René Descartes to the ‘hard problem’ of consciousness, a phrase coined in 1994 by the Australian philosopher David Chalmers, and the question ‘What is it like to be a bat?’ of American philosopher Thomas Nagel, it is shown that there is no generally agreed definition of consciousness. Subjectivity (or phenomenality), qualia, and the ideas of philosopher Daniel Dennett are also discussed.
The ‘hard problem’
What is consciousness? This may sound like a simple question but it is not. Consciousness is at once the most obvious and the most difficult thing we can investigate. We seem either to have to use consciousness to investigate itself, which is a slightly weird idea, or to have to extricate ourselves from the very thing we want to study. No wonder philosophers have struggled for millennia with the concept; and for long periods scientists refused even to study it. The good news is that, in the 21st century, ‘consciousness studies’ is thriving. Psychology, biology, and neuroscience have reached the point where they are ready to confront some tricky questions: What does consciousness do? Could we have evolved without it? Is consciousness an illusion? What do we mean by consciousness, anyway?
This does not mean that the mystery has gone away. Indeed, it is as deep as ever. The difference now is that we know enough about the brain to confront the problem head on. How on earth can the electrical firing of millions of tiny brain cells produce this—my private, subjective, conscious experience?p. 2↵
If we are going to get anywhere with understanding consciousness, we have to take this problem seriously, either by solving it or by showing why it is not really a problem at all. Some people claim to have solved the mystery of consciousness with grand, unifying theories, quantum physics, or spiritual theories involving mysterious powers of consciousness—but most simply ignore the yawning chasm, or ‘fathomless abyss’, between the physical and mental worlds (Figure 1). As long as they ignore this problem they are not really dealing with consciousness at all.
This problem is a modern incarnation of the famous mind–body problem with which philosophers have struggled for more than 2,000 years. The trouble is that in ordinary human experience there seem to be two entirely different kinds of thing, with no obvious way to bring them together.
p. 3↵On the one hand, there are our own experiences. Looking up from my work I can see trees, fields, and a bridge. I can hear the sound of the river and the buzzing of a fly. I can enjoy the warmth and familiarity of my own room, and wonder whether that scratching noise is the cat trying to get in. All of these are my own private experiences and they have a quality I cannot convey to anyone else. I may wonder whether your experience of green is the same as mine or whether coffee has exactly the same smell for you as it does for me, but I cannot find out. These ineffable (or indescribable) qualities are what philosophers call qualia (although there is much dispute about whether qualia exist or whether the concept is meaningful at all). The redness of that shiny red mug is a quale; the soft feel of my cat’s fur is a quale; and so is that smell of coffee. These experiences seem to be real, vivid, and undeniable. They make up the world I live in. Indeed, they are all I have.
On the other hand, I really do believe that there exists a physical world out there that gives rise to these experiences. I may have doubts about what it is made of, or about its deeper nature, but I do not doubt that it exists. If I denied its existence I would not be able to explain why, if I go to the door, I shall probably find the cat there—and if you came by you would agree that there was now a cat trailing muddy footprints across my desk.
The trouble is that these two aspects of the world seem to be utterly different. There are real physical things, with size, shape, weight, and other attributes that we can measure and agree upon, and then there are private experiences—the feeling of pain, the colour of that apple as I see it now.
Throughout history most people have been dualists, believing in two different realms or worlds. This is also true of most non-Western cultures today with surveys suggesting it is true of most educated Westerners as well. This dualist belief begins early in life with children of 4 or 5 years old happily dividing the world into mental and physical things.
p. 4↵The major religions are almost all dualist, especially Christianity and Islam, which rely on the notion of an eternal, non-physical soul that can survive death and end up in heaven or hell. Many Hindus believe in the Atman or divine self, although the Advaita school advocates a non-dual philosophy that is becoming increasingly popular in the modern world. Non-duality is also found in the Buddhist concept of anatta, or no-self. The trouble is that it’s hard to let go of the idea that ‘I’ and my private experiences are distinct from my body and brain.
Even among non-religious people, dualism is still prevalent. Popular New Age theories invoke the powers of mind, consciousness, or spirit, as though they were an independent force; and alternative therapists champion the effect of mind over matter, as though mind and body were two separate things. Such dualism is so deeply embedded in our language that we may happily refer to ‘my brain’ or ‘my body’; as though ‘I’ am separate from ‘them’.
In the 17th century the French philosopher René Descartes proposed the most famous dualist theory (Figure 2). Known as Cartesian dualism, this is the idea that mind and brain consist of different substances: the mind is non-physical and non-extended (i.e. it takes up no space); the body and the rest of the physical world are made of physical, or extended, substance. The trouble with this is obvious. How do the two interact? Descartes proposed that they meet in the tiny pineal gland in the centre of the brain, but this only staves off the problem a little. The pineal gland is a physical structure and Cartesian dualism provides no explanation of why it, alone, can communicate with the mental realm.
The interaction problem bedevils any attempt to build a workable dualist theory, which is probably why most philosophers and scientists completely reject dualism in favour of some kind of monism (the idea that there is only one kind of reality); but the p. 5↵options are few and problematic. Idealists make the mind fundamental but then must explain why and how there appears to be a consistent physical world. Neutral monists reject dualism but disagree about the fundamental nature of the world and how to unify it. A third option is materialism and this is by far the most popular among scientists today. Materialists take matter as fundamental, but then they face the problem that this book is all about—how to account for consciousness. How can a physical brain, made purely of material substances and nothing else, give rise to conscious experiences or ineffable qualia?
p. 6↵This problem is called the ‘hard problem’ of consciousness, a phrase coined in 1994 by the Australian philosopher David Chalmers. He wanted to distinguish this serious and overwhelming difficulty from what he called the ‘easy problems’. The easy problems, according to Chalmers, are those that in principle we know how to solve, even if we have not yet done so. They include perception, learning, attention, and memory; how we discriminate objects or react to stimuli; how being asleep differs from being awake. All these are easy, he says, compared with the really hard problem of experience itself.
Not everyone agrees. Some claim that the hard problem does not exist; that it depends on a false conception of consciousness, or on drastically underestimating the ‘easy’ problems. The philosopher Massimo Pigliucci asks ‘What hard problem?’ calling it an illusion caused by ‘the pseudo-profundity that often accompanies category mistakes’. And American philosopher Patricia Churchland calls it a ‘hornswoggle problem’, arguing that we cannot, in advance, decide which problems will turn out to be the really hard ones. It arises, she claims, from the false intuition that if we explained perception, memory, attention, and all the other details, there would still be something left out—‘consciousness itself’.
These are important objections. So before we go any further we must delve into what, if anything, ‘consciousness itself’ might mean.
What is it like to be a bat? This curious question looms large in the history of consciousness studies. First asked in the 1950s, it was made famous by the American philosopher Thomas Nagel in 1974. He used the question to challenge materialism, to explore what we mean by consciousness, and to see why it makes the mind–body problem so intractable. What we mean, he said, is subjectivity. If there is something it is like to be the bat—something for the bat p. 7↵itself—then the bat is conscious. If there is nothing it is like to be the bat, then it is not (Box 1).
Box 1 Defining consciousness
There is no generally agreed definition of consciousness, but the following are ways often used to talk about it.
‘What it’s like to be …’: If there is something it is like to be for an animal (or computer; or baby) then that animal (or computer; or baby) is conscious. Otherwise it is not.
Subjectivity or phenomenality: Consciousness means subjective experience or phenomenal experience. This is the way things seem to me, as opposed to how they are objectively.
Qualia (singular: quale, pronounced qua-lay): The ineffable subjective qualities of experience, such as the redness of red or the indescribable smell of turpentine. Some philosophers claim that qualia do not exist.
The hard problem: How do subjective experiences arise from objective brains?
So think, for example, of the mug, mouse mat, or book on your table. Now ask yourself—what is it like to be the mug? You will probably answer that it is like nothing at all; that mugs cannot feel, that china is inert, and so on. You will probably have no trouble in opining that mugs and mats are not conscious. But move on to worms, flies, bacteria, or bats and you may have more trouble. You do not know, and have no idea how to find out, what it is like to be an earthworm. Even so, as Nagel points out, if you think that there is something it is like to be the worm, then you believe that the worm is conscious.
Nagel chose the bat as his example because bats are so very different from us. They fly in the dark, hang upside-down from p. 8↵trees or in damp caves, and use sonar as well as vision. They emit rapid bursts of high-pitched squeaks while they fly and then, by analysing the echoes that come back to their sensitive ears, learn about the world around them.
What is it like to experience the world this way? It is no good imagining that you are a bat because an educated, speaking bat would not be a normal bat at all; conversely, if you became a normal bat and could not think or speak then you would not be able to answer your own question.
Nagel argued that we can never know the answer to this question and he concluded that the problem is insoluble. For this reason he is dubbed a mysterian. Another mysterian is the American philosopher Colin McGinn, who argues that we humans are ‘cognitively closed’ with respect to consciousness. That is, we have no hope of understanding it, just as a dog has no hope of being able to read the newspaper he so happily carries back from the shops. Psychologist Stephen Pinker agrees: we may be able to understand most of the detail of how the mind works, yet consciousness itself may remain forever beyond our reach.
Not many people share Nagel’s pessimism, but his question has proved helpful in reminding us what is at stake when we talk about consciousness. It is no good learning about perception, memory, intelligence, or problem-solving as purely physical processes and then claiming to have explained consciousness. If you are really talking about consciousness, then you must deal with subjectivity. Either you must actually solve the hard problem and explain how subjectivity arises from the material world or, if you claim that consciousness is an illusion or even that it does not exist at all, you must explain why it appears so strongly to exist.
Subjective experience or ‘what it’s like to be … ’ is also called phenomenality, or phenomenal consciousness, terms coined by p. 9↵American philosopher Ned Block. He divides phenomenal consciousness (what it is like to be in a certain state) from access consciousness (availability for use in thinking or guiding action and speech). Others deny there is any difference, but phenomenal consciousness (or phenomenality, or subjectivity) is what Nagel was talking about and is the core of the problem of consciousness.
With these ideas in mind, we are ready to face a fundamental divide in consciousness studies. This concerns the following question: Is consciousness an extra ingredient added to our ability to perceive, think, and feel, or is it inseparable from being able to perceive, think and feel? To put it another way, are qualia or subjective experiences something in addition to being a living, thinking, feeling creature? This really is the key question on which the rest depends, and you might like to decide now on your own answer, for the implications either way are quite striking.
On the one hand, if consciousness is an extra added ingredient then we naturally want to ask why we have it, what it’s for, what it does, and how we got it. We might imagine that we could have evolved without it, and so we want to know why we have this added extra, what advantages it gave us, and whether it evolved in other creatures too. This means that the hard problem is indeed hard; and the task ahead is to answer these difficult questions.
On the other hand, consciousness might be intrinsic to complex biological processes and inseparable from them. This is the view in both materialism (everything in the universe is matter) and functionalism (any animal or machine that carried out the appropriate functions would necessarily be conscious too). In this case there is no need to ask why consciousness evolved, because any creature that evolved with intelligence, perception, memory, and emotions would necessarily be conscious as well. There is no added extra and no sense in talking about ‘consciousness itself’ or ‘ineffable qualia’. Thinking about consciousness this way, there is no deep mystery, and no hard problem. What we need to do is p. 10↵explain why there seems to be a hard problem and why we seem to be having ineffable, non-physical, conscious experiences. In other words, consciousness is an illusion because neither consciousness nor the hard problem are what they seem to be. So the task is to explain how the illusions come about.
If the implications of this dichotomy seem hard to grasp, a thought experiment might help.
Imagine someone who looks like you, acts like you, and speaks like you, but who is not conscious at all. This outwardly identical other you has no inner world, no conscious experiences, and no qualia; all its actions are carried out ‘in the dark’ without the light of awareness. This unconscious creature—not some half-alive Haitian corpse—is the ‘philosophical zombie’.
Zombies are easy to imagine, but could they exist? This apparently simple question leads to a world of philosophical difficulties because if zombies can exist then physicalism is false and some kind of dualism has to be true.
On the ‘yes’ side are those who believe it possible to have two apparently identical systems; one conscious, the other unconscious. Chalmers says ‘yes’, claiming that zombies are not only imaginable but possible—in some other world if not in this one. He imagines his zombie twin who behaves exactly like the real Chalmers but has no conscious experiences, no inner world, and no qualia. All is dark inside the mind of zombie-Dave. Other philosophers have dreamed up thought experiments involving a zombie Earth populated by zombie people, or speculated that some real live philosophers might actually be zombies pretending to be conscious.
On the ‘no’ side are those who believe the whole idea of zombies is absurd, including both Churchland and American philosopher p. 11↵Daniel Dennett. The idea is ridiculous, they claim, because any system that could walk, talk, think, play games, choose what to wear, or enjoy a good dinner would necessarily be conscious. When people imagine a zombie they cheat by not taking the definition seriously enough. So if you don’t want to cheat, remember that the zombie has to be completely indistinguishable from a normal person. It won’t help to ask the zombie questions about its experiences or philosophy, because by definition it must behave just as a conscious person would. If you really follow the rules, the critics say, the idea disappears into nonsense (Figure 3).
It should now be easy to see that the zombie is a vivid way of thinking about the key question: Is consciousness an added extra that we conscious humans are lucky to have, or does it necessarily come along with all our evolved skills of perceiving, thinking, and feeling? If you believe that it’s an added extra, then we could all have evolved as zombies instead of as conscious people and you may be tempted to ask why we did not. You might even start p. 12↵wondering whether your best friend is a zombie. But if you believe that consciousness is inseparable from the skills we humans have, then zombies could not exist and the whole idea is daft.
I think the whole idea is daft. Nevertheless, it remains extremely alluring, largely because it is so easy to imagine a zombie. Yet being easy to imagine something is not a good guide to the truth. So let’s consider another aspect of the same problem—whether consciousness does anything.
The phrase ‘the power of consciousness’ is common in popular discourse. The idea is that consciousness is some sort of force that can directly influence the world—either by acting on our own bodies, as when ‘I’ consciously decide to move my arm and it moves—or, more controversially, in things like psychic healing, telepathy, or ‘mind over matter’. Like the zombie, this ‘power’ is easy to imagine. We can visualize our conscious mind controlling our bodies and influencing things. But does this idea make any sense? As soon as you remember that consciousness means subjectivity or phenomenality, then the idea seems less plausible. How could ‘what it’s like to be’ something act as a force or power? How could my experience of the green of that tree cause something to happen?
One way to explore this idea is to ask what would happen if you took someone’s consciousness away. Obviously, if consciousness has any power at all, what would be left could not be a zombie because the zombie must, by definition, be indistinguishable from a conscious person. So you would be left with someone who was different from a conscious person because … what?
Perhaps you think we need consciousness to make decisions, but neuroscience shows us how the brain makes decisions and it does not seem to need an extra, added force to do so. Artificial systems are making increasingly complex decisions without needing a consciousness module. The same goes for seeing, hearing, p. 13↵controlling action, and many other human abilities. The more we learn about the brain the less room there is for consciousness to play a role. Perhaps you think it is needed for aesthetic appreciation, creativity, or falling in love, but, if so, you would have to show that these things are done by consciousness itself rather than by the workings of a clever body and brain.
All this leads to the awkward notion that perhaps consciousness does nothing, and other oddities point the same way. For example, think about people catching cricket balls, playing table tennis, or interrupting fast-flowing conversations. These quick actions may seem to be done consciously, but is it the consciousness itself that makes them happen? In fact, as we shall see, such actions happen too fast. Could consciousness, then, be completely powerless? One version of this idea is epiphenomenalism—the idea that consciousness is a useless by-product or epiphenomenon. But this is a very curious notion because it entails consciousness actually existing but having no effects on anything else. And if it has no effects it is hard to see how we could end up worrying so much about it—or even talking about it.
But epiphenomenalism is not the only way of understanding consciousness as being powerless. An alternative is that any creature that can see, feel, think, fall in love, and appreciate a fine wine will inevitably end up believing they are conscious, imagining zombies are possible, and thinking that consciousness does things. The bottom line for this kind of theory is that we are deluded; we feel as though our consciousness is a power or added ability and so we believe it is, but we are wrong. If this theory needs a name, we might call it ‘delusionism’.
I think this is the right way to think about consciousness, but it implies that our ordinary assumptions about our own minds are deeply misguided. Could we really be so wrong? And if so, why? Perhaps we should take a closer look at some of those everyday assumptions.
The most natural way to think about consciousness is probably something like this. The mind is like a private theatre inside my head, where I sit looking out through my eyes. But this is a multi-sensational theatre with touches, smells, sounds, and emotions. And I can use my imagination to conjure up sights and sounds as though seen on a mental screen or heard by my inner ear. All these thoughts and impressions are the ‘contents of my consciousness’ and ‘I’ am the audience of one who experiences them (Figure 4).
This theatre imagery fits happily with another common image of consciousness—that it flows like a river or stream. In the 19th century, the ‘father of modern psychology’, William James, coined the phrase ‘the stream of consciousness’ and it seems apt enough. Our conscious life really does feel like a flowing stream of sights, sounds, smells, touches, thoughts, emotions, worries, and joys—all of which happen, one after another, to me.
This way of conceiving of our own minds is so easy, so natural, that it hardly seems worth questioning. Yet when we get into an intellectual muddle, as we have with the problem of consciousness, it may be worth challenging some basic assumptions—in this case, these apparently innocent analogies.
The strongest challenge comes from Dennett who argues that while most people are happy to reject Cartesian dualism, they still retain dualist thinking in imagining what he calls the Cartesian theatre. This is not just the analogy of the mind with a theatre, but the notion that somewhere in the mind or brain there must be a place and time at which everything comes together and ‘consciousness happens’; or a finishing line in the brain’s activities, after which things mysteriously become conscious or ‘enter consciousness’.
p. 15↵This has to be false, claims Dennett, because the brain is a parallel, distributed processing system with no central headquarters and no place in which ‘I’ could sit, making decisions and watching the show as things pass through my consciousness. Instead, the many different parts and processes of the brain just get on with their own jobs, communicating with each other when necessary, and with no central control. What, then, could correspond to the theatre of consciousness? Somehow we have to understand how this feeling of being a conscious self who is having a stream of experiences comes about in a brain that really has no inner theatre, no show, and no audience.
p. 16↵Dennett coined the term ‘Cartesian materialist’ to describe people who claim to reject dualism but still believe in the Cartesian theatre. Few admit to being one. Yet ideas such as the stream of consciousness and the theatre of the mind remain as popular as ever. They may, of course, be right, and if so the task of a science of consciousness is to explain what that metaphorical theatre corresponds to in the brain and how it works. But I rather doubt they are. Exploring a little more about how the brain works may help us to see why.