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- Herausgeber: John Wiley & Sons
- Kategorie: Geisteswissenschaft
- Serie: Key Concepts in Philosophy
- Sprache: Englisch
Each of us, right now, is having a unique conscious experience. Nothing is more basic to our lives as thinking beings and nothing, it seems, is better known to us. But the ever-expanding reach of natural science suggests that everything in our world is ultimately physical. The challenge of fitting consciousness into our modern scientific worldview, of taking the subjective “feel” of conscious experience and showing that it is just neural activity in the brain, is among the most intriguing explanatory problems of our times.
In this book, Josh Weisberg presents the range of contemporary responses to the philosophical problem of consciousness. The basic philosophical tools of the trade are introduced, including thought experiments featuring Mary the color-deprived super scientist and fearsome philosophical “zombies”. The book then systematically considers the space of philosophical theories of consciousness. Dualist and other “non-reductive” accounts of consciousness hold that we must expand our basic physical ontology to include the intrinsic features of consciousness. Functionalist and identity theories, by contrast, hold that with the right philosophical stage-setting, we can fit consciousness into the standard scientific picture. And “mysterians” hold that any solution to the problem is beyond such small-minded creatures as us.
Throughout the book, the complexity of current debates on consciousness is handled in a clear and concise way, providing the reader with a fine introductory guide to the rich philosophical terrain. The work makes an excellent entry point to one of the most exciting areas of study in philosophy and science today.
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Veröffentlichungsjahr: 2014
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Table of Contents
Key Concepts in Philosophy
Title page
Copyright page
Dedication
Acknowledgments
1: The Problem
The Knowledge Argument
Zombies!
The Long-Distance Driver
Androids
A Few Disclaimers, Definitions and Distinctions
Further Reading
2: Mysterianism
McGinn's Permanent Mysterianism
Pessimistic Temporary Mysterianism
Optimistic Temporary Mysterianism
Conclusion: A Modest Proposal?
Further Reading
3: Dualism
From Substance to Property Dualism
Interactionist Dualism
Epiphenomenal Dualism
Further Reading
4: Nonreductive Views
Russell's Gap and Physical Theory
Strawson's Realistic Monism
Stoljar's Ignorance Hypothesis and Chalmers's Panprotopsychism
Neutral Monism
Worries About Nonreductive Views
Further Reading
5: The Identity Theory
Block's Distinction Between “Access” and “Phenomenal” Consciousness
Block's Identity Theory
Worries, Replies, and More Worries About Identity Theory
The Distinction Between A-Consciousness and P-Consciousness, One Last Time
Further Reading
6: Functionalism
A Functional Characterization of Consciousness
What Functional Roles Matter for Consciousness?
What is the Function of Consciousness?
Functionalist Theories of Consciousness
Troubles for Functionalism
Further Reading
7: First-Order Representationalism
Theories of Representation
Transparency and “Standard” First-Order Representationalism
Prinz's AIR Theory
Worries for FOR
Further Reading
8: Higher-Order Representationalism
The Transitivity Principle
The Traditional Higher-Order Approach
The Self-Representational Theory
Higher-Order Global States
Worries for the Higher-Order Approach
Conclusion
Further Reading
References
Index
Key Concepts in Philosophy
Copyright © Josh Weisberg 2014
The right of Josh Weisberg to be identified as Author of this Work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.
First published in 2014 by Polity Press
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ISBN-13: 978-0-7456-5344-0
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For Ashley, for everything
Acknowledgments
Most of what I know about serious philosophy, and especially about the problem of consciousness, I learned from David Rosenthal. My sincere thanks to David for all his guidance; this book would not exist without him. Also, I've greatly benefited from the work of two of the best folk working on consciousness today: Ned Block and David Chalmers. Ned and Dave, both in their writings and in person, have challenged my own thinking on these issues and this has done much to improve the quality of the material herein.
My thinking on consciousness has been deeply shaped by an ongoing (and sometimes drunken) debate I've been carrying out for years with Pete Mandik, Uriah Kriegel, Richard Brown, Ken Williford, and Dave Beisecker, among many others. It still amazes me that we get paid to do what we do, as we'd be doing it anyway, so long as there's a place where we can gather for beers and people don't mind us yelling about swamp zombies and hyper-encephalated squirrels. Thanks as well to the CUNY Cognitive Science lecture series (run by David Rosenthal) for all the incredible talks and discussions late into the New York night.
Thanks to my wonderful colleagues at the University of Houston, especially Jim Garson and David Phillips who gave me advice and encouragement as this process moved forward. Thanks to Tamler Sommers for food, football, and philosophy. Thanks to Cynthia Freeland for the cookies and conversation. And thanks to Bredo Johnsen for … well, just for being Bredo Johnsen! It is truly a gift in life when you love coming to work every day.
I presented versions of this material three times to graduate seminars at UH, and each time I received excellent feedback and advice. Many thanks to those students for their energy and enthusiasm. I also benefited immensely from co-teaching a workshop on philosophical theories of consciousness with Uriah Kriegel at the “Towards a Science of Consciousness” conference in Tucson in 2010 and 2012. Thanks to Uriah for that and all the wonderful conversations we've had over the years.
Thanks to my editor, Emma Hutchinson, and Pascal Porcheron and David Winters, at Polity Press. Emma's sure hand has made this process easy from the very beginning. Cheers! And thanks to Ken Williford who read the whole draft and provided excellent comments and criticisms, as well as insightful help in the proper use of umlauts.
Since taking on this book project, my sons Winston and Franklin were born. I love them with all my heart, but they are a handful, to say the least! Therefore it would have been impossible to write this book without the help of my friends and family. Thanks especially to Clint and Amy Harris, for Friday night cul-de-sac and more, and to my in-laws, Farrell and Peggy Hope, who have swooped in to the rescue multiple times! My mother Judy Weisberg and my late father Robert Weisberg have been incredibly supportive throughout my life – they always made me feel I could do anything and that I should follow my heart. Thanks, mom and dad! But none of this happens without the endless love and encouragement (and wisdom and backbone and childlike joy) that I've received from my wonderful wife, Ashley Hope. Truly my better half. This book is dedicated to her.
1
The Problem
What is the problem of consciousness? If there's one most pressing worry about consciousness in contemporary philosophy, it's what philosopher David Chalmers calls “the hard problem” (Chalmers 1996). It's the problem of explaining why anything physical is conscious at all. More specifically, why do certain physical brain processes result in the subjective experience of color, rather than experiences of sound or no experiences whatsoever? The problem is a version of an older philosophical conundrum, the so-called “mind–body problem,” famous from the work of René Descartes. The hard problem of consciousness is where much of the fighting over the mind–body problem ends up after the rise of modern psychology, cognitive science, and neuroscience. Consciousness seems to be the remaining bit that fails to fit nicely into the modern scientific worldview. Even after we've explained all of what the brain does, down to the finest neural detail, the hard problem of consciousness appears unanswered. The hard problem, and philosophers' attempts to deal with it, is the main focus of this book.
But what is consciousness? As with many philosophical questions, even agreeing on the thing we disagree about is difficult! How we pick out consciousness in the first place can have big implications for how hard the hard problem appears. If we define consciousness as “the mysterious, unknowable core of human experience,” then it's not surprising that consciousness seems inexplicable. But if we define consciousness as “whatever causes our verbal reports about how we feel,” then we may be defining a real mystery out of existence at the get-go. So it would be nice if we can find a way to characterize consciousness that neither builds in unsolvable mystery, nor rules it out by stacking the explanatory deck. While there isn't a single agreed-upon definition in contemporary philosophy, unfortunately, we can focus on a set of puzzling “thought experiments” – imagined scenarios where innocent-looking steps lead us to philosophical worries – to zero in on what's at issue. And while not every philosopher agrees that the thought experiments carry great meaning, all can agree that something must be said to explain the puzzlement they generate. What's more, much of the contemporary literature on the philosophical problem of consciousness at least touches on some or all of these imagined scenarios, so they are needed background knowledge for anyone wanting to go down this particular rabbit hole.
The Knowledge Argument
The first thought experiment is called the “knowledge argument” against physicalism (Jackson 1982). Physicalism is the claim that everything is ultimately made of physical stuff like atoms and nothing else. Physicalism is a central feature of the standard scientific worldview of today. The knowledge argument seems to show that consciousness cannot fit into that worldview. The thought experiment brings out an everyday intuition that many of us have before we get near a philosophy classroom. Intuitions are generally unarticulated beliefs or gut feelings we have about certain subjects. For example, most people feel it's wrong to kick a puppy, even if we can't really justify why that is. A key job of philosophy is exposing these underlying intuitions and investigating whether they're to be kept or thrown out as we develop a deeper understanding of a subject. The everyday intuition brought out by the knowledge argument is the idea that a person blind from birth will never really know all that sighted folk know about colors. A blind person might ask us to describe red. We can say things like “it's a feature of objects which can vary independently of shape.” The blind person might say, “Oh, you mean like texture!” But we'd have to say that's not it. We might say, “Red is hot, like the sound of a trumpet.” But we'd quickly recognize that there's something we can't put into informative words, something that's left out of any description we offer to our blind friend. That left-out something, whatever it is, is a key element in the problem of consciousness.1
The knowledge argument takes this intuition and makes a more general point about the limits of physicalism and the scientific worldview. Instead of imagining (or actually talking to!) a blind person, we are asked to imagine a super-scientist of the future. She lives in a time when all the outstanding problems of science have been solved. What's more, she has a prodigious memory and an unfailing ability to digest and understand science. In fact, she has gone through all the relevant material and knows all of the facts of a completed science. But this super-scientist – let's call her Mary, following Frank Jackson who introduced this story in 1982 – has been brought up in a very special environment. Everything in her world is black and white and shades of grey (perhaps this is achieved by fitting her with special lenses which make the world look like it does on a black-and-white TV set). She has never in her life seen colors. Now for the crucial intuition-tapping question: when she's finally released from her black-and-white captivity and sees a red rose for the first time, does she learn anything new? Most of us would say that she does learn something new. She learns that this is what red looks like, that this is what it's like for one to see red. This seems like a fact she couldn't have known beforehand. But given that she already knew all of the facts of science, this must be a fact beyond the reach of science, something left out of science altogether! So there are facts beyond the scientific worldview. And since science plausibly contains all the facts about physical stuff – where all the atoms are, how they interact, and so on – this new fact must be about something that isn't physical. So physicalism, which claims that, ultimately, all the facts are physical facts, must be incorrect.
And what does this tell us about consciousness? When we think about it, the fact that Mary doesn't know before her release is a fact about her (and others') experience. It is a fact about what it's like to see red from the inside. She already knows all the “outside” facts about red: that it's feature of the surfaces of some physical objects, that such surfaces reflect light at certain wavelengths, and so on. She even knows, in neurological terms, what happens in normal observers when they see red: cone cells on their retinas fire in a particular ratio, activity occurs in area V4 of their brains, and so on. But none of these scientific facts helps her to know what it's like to experience red. That is a fact about conscious experience. There's a special quality there – the “redness” of red. Philosophers label these sorts of special qualities of consciousness “qualia.” Mary lacks knowledge of red qualia. And no amount of scientific information can give her that knowledge, or so it seems. There is clearly something special about conscious experience.
So are we any closer to figuring out just what the problem of consciousness is all about? From the knowledge argument, we can see that consciousness possesses special qualities, and these qualities seemingly defy description. If you haven't experienced them yourself, no amount of what philosopher David Lewis calls “book learning” will tell you (Lewis 1988). And as philosopher Ned Block says, channeling Louis Armstrong, “if you gotta ask, you're never gonna know!” (Block 1978). And if qualia can't be informatively described, then they can't be explained scientifically, or so it seems. We are left with a hard problem! Now, not all philosophers agree with this bleak assessment of consciousness, but it's hard to deny that there at least appears to be an explanatory puzzle here. Throughout this book, we'll consider a range of responses to the problem, from those who accept the knowledge argument and try to sketch out what must be added to our worldview to fit in consciousness, to those who argue that the argument is misleading, inconclusive, or completely invalid. Those theorists have to explain why it is that consciousness prima facie poses a problem and then explain where consciousness fits in the current physicalist worldview. But all that matters so far is that we begin to get a feel of the philosophical worry here. A second thought experiment may help to bring that worry out further.
Zombies!
This thought experiment asks us to imagine, if we can, a creature just like us in all physical respects, right down to the last atom, but lacking consciousness (Chalmers 1996). Could you, for example, have a perfect physical doppelgänger, a molecule-for-molecule twin, who nonetheless fails to be conscious? This sort of nonconscious physical twin is called a “zombie” by philosophers. Unlike the zombies in monster movies, these “philosophical zombies” look exactly like us from the outside. But inside “all is dark” – there is no experience at all. Consider that many of the tasks we perform repeatedly in a day can become automated, so that we can do them on “auto-pilot.” For example, if I have to wash the dishes (a task I perform many times a week at our house!), I may become so lost in philosophical or football-related thought that I lose focus on the dishes and may not even be aware at all that I've finished several plates and bowls. Might it be that a zombie does everything on autopilot? If such a creature is merely conceivable – if we can form a coherent mental picture of one – that may show that consciousness is something over and above a physical process. If consciousness were nothing more than a physical process, we shouldn't even be able to imagine zombies. Or so some philosophers argue.
Consider, by contrast, trying to conceive of something physically identical to a mountain, yet somehow not being a mountain. It's hard to even figure out what this means. That's because a mountain is nothing more than a huge pile of basic physical bits. If you have all those bits arranged in the right way, you've got a mountain. That's all there is to being a mountain. Because of this, philosophers say that mountains supervene on physical matter. Now back to our zombie twin. Unlike the mountain, it seems that we can at least imagine a creature just like us physically but lacking consciousness. It seems that the supervenience of consciousness on physical matter is not a straightforward affair. There seems to be at least a conceptual gap between consciousness and physical stuff, in contrast to the mountain case. To take another example, imagine a molecule-for-molecule physical duplicate of yourself, doing everything that you do, but not breathing. Or walking. Again, it seems impossible to imagine what's being asked. If a creature has all the molecules we do, and it's using them to exchange oxygen and carbon dioxide with the atmosphere, then it is breathing! That's all there is to it. Likewise, if a creature shares our molecular structure and is moving in a controlled way on two legs, it's walking. So breathing and walking supervene on our physical makeup and the action of our physical systems. But that's not obviously so for consciousness. It's not clear that all there is to consciousness is the performing of some action by a physical system. And that's the problem. What is consciousness if it's more than just something physical? Figuring out what consciousness is seems harder than figuring out what breathing is.
And again we can focus on just what's seems to be missing in the zombie case to try to pin down just what consciousness amounts to. When we engage in certain behaviors, it feels a certain way to us – there is something it's like to be us, for us, as we do these things.2 Not so for our imagined zombie twins. This “feel,” this “something that it's like for us,” is the feature of the mind at issue in philosophical debates about consciousness. It's the way experience feels from the inside, for us, subjectively. And due to the apparent slippage between consciousness and physical stuff, we are faced with a puzzle. Given the success of physical science in explaining how we work, we might expect that everything about us is explainable in this way. But consciousness seems to buck the trend. It may well mark the limits of natural science. There may be a special inner core of the mind, a special property of experience, lying forever beyond the reach of scientific theory. This is the problem of consciousness.
The Long-Distance Driver
Yet another thought experiment, this one far closer to home, may help get at what's at issue. Rather than imagining super-scientists of the future or strange nonconscious doppelgängers, imagine (or recall, if you can) driving for a long spell down a stretch of relatively deserted highway (Armstrong 1981). If you're like me washing the dishes, you may have found that you've driven for some time while lost in thought. You then snap back to reality and focus again on the highway in front of you. While you were “out,” you didn't lose control of the car (hopefully!). That means you must have taken in visual information and used it to handle the car properly. But something was missing, something that clicked back on when you noticed the road again. That something is arguably conscious experience. It's what's lacking during the autopilot moments and what returns when you're aware of the road again. Now this thought experiment doesn't generate the puzzle the others do, but that may help us to be more clear about the subject matter here. Sometimes our mental states occur consciously, sometimes they don't. Now, what does that difference amount to? And can we explain the difference in brainy terms?
Androids
Yet another way to see the problem is to think about what we'd do if we ever met a really intelligent android. Imagine a spaceship brings a visitor from outer space to our world. It can speak our language, and we eagerly converse with this being. It tells us of its home far, far away, the trials and tribulations of spaceflight, the trouble with tribbles, and so forth. At this point, we'd probably all think such a creature must be conscious. But then imagine that we notice some wires poking out from its scalp and we ask it if it's an android. Yes, it says, and dramatically pulls off its faceplate, revealing a grid of sensors, lights, gears, and circuits! At this point, are we so sure that the being is conscious in the way we are? Many people become hesitant to attribute consciousness to such a creature, once they learn it's a robot. Why is this? Well, one aspect felt to be missing is inner feelings, the emotions and sensations we experience. An intelligent android might be able to reason and remember, perhaps even better than we do. But there seems to be an open question as to whether or not the creature is conscious.
We then might wonder if there's any further test we can do to the robot to determine once and for all if it's conscious. But what could we possibly do? We might kick it in the shins and see how it reacts. But what if it yells out and starts hopping around? Can we be sure that this is because it's in pain and not just because it's following a program of avoidance and evasion? Couldn't it just be “going through the motions”? So maybe we can try to observe its electronic “brain” in action when we kick it in the shins. But again, how would this help? No doubt we'd see all sorts of complex mechanical interactions. Circuits would allow energy to flow through various processors, analyzers would process data, and motor programs and reactions would be triggered. But is there anything there to tell us that those actions, no matter how complex, are conscious? That is, is there anything to tell us that there's subjective inner experience, replete with the “ouchy” quality of pain, going on? It seems like all could go on in the absence of consciousness. And even if consciousness is there, we don't seem to know how to detect it. As you can see, consciousness is becoming rather slippery!
And note that we'd have the same exact problem even if the visitor turned out to be fully organic and not an android at all. Imagine our visitor is filled with green goo. Could that tell us if it were conscious? How? Why is gooey organic material any better than non-gooey mechanical stuff? We seem to be in the same pickle. Even if the alien told us, in English, that it is in serious pain, that it hurts, how do we know that it's not just saying that because of some automatic, autopiloted response, one that occurs without the kind of inner quality we feel? At this point, you may be worried that we can't even tell if another human is conscious! And that is a worry, called by philosophers the problem of other minds. But, at least in our case, we can gain some traction by noting that we're all made of the same sort of stuff, that we have the same evolutionary backgrounds, that we have relevantly similar brain structures, and so on. But still, the very fact that this sort of worry is possible at all shows that there's something weird about consciousness. We know it intimately in our own case – what is better known to me than my conscious pains and pleasures? But we can only attempt to infer it in others, and it looks like a space opens up for us to be wrong about its presence. Now, this is nuts. Surely I can know that you're in pain when I kick you in the shins with my cowboy boots. So it seems, but we can feel the slippage here between conscious experience and other things we do, like breathing and walking. Some philosophers take this slippage to indicate a serious metaphysical rift in reality, a place where the normal physical rules break down. Others think that, despite first (or even second or third) appearances, consciousness in the end can be roped back into the corral of science. But it will take some doing, if it can be done at all.
A Few Disclaimers, Definitions and Distinctions
I hope that you have a bit of a feel for the problem of consciousness. We will need to become more precise as we go, but the best way to really grasp the key issues is to grapple with the pros and cons of various theories of consciousness offered by philosophers and scientists. This is the best way to learn about any complex and controversial subject: study the back-and-forth tennis match of ideas. It's hard to understand one theory without getting a good idea of its rivals, and it's hard to know what we really think if we don't understand views opposed to ours. This task will take up the rest of the book. We'll survey theories holding that consciousness is radically different from anything else in the universe and thus requires special metaphysical maneuvering to fit into our understanding. We'll look at views that see consciousness as just another problem for science to conquer without the need for major philosophical renovations. And we'll even look at views claiming that any deeper understanding of consciousness is beyond us. But first we need to lay out a few helpful ideas in order to make our journey more manageable. And we'll need to say a bit about what this book is not. That task will take up the rest of this chapter.
While this book deals with the most persistent and central philosophical worry about consciousness, it is distinctly a work of what is loosely known as “analytic philosophy,” the sort of philosophy focused deeply on issues of language and logic, an approach inspired by the work of Gottlob Frege, Bertrand Russell, Ludwig Wittgenstein, Rudolf Carnap, and others from the early and mid-part of the twentieth century. This approach, in its purest form, tries to first analyze our concepts, and then to see what those concepts, properly clarified, might pick out in the world. Using the modern logic of Frege as a central tool (amended with the modal logic of Kripke and others, from the 1960s on), analytic philosophers try to spell out exactly what our concepts, or the words that express them, mean or refer to when precisely presented in logical language. Then we see what must follow about the world (or about some possible, but nonactual world) to make those terms refer or to make sentences using those terms true. The initial grand goals of analytic philosophy, of laying out sharply just what can and cannot be said in philosophy and elsewhere, have faded, undermined by both internal and external worries (see Schwartz 2012 for a fine review of this recent history). But the basic idea of using precise logic and language to delimit philosophical problems remains. This is both a blessing and a curse. On the one hand, we arrive, when all works well, at clear, precise statements of what we're on about. On the other, there is often a fetishistic overuse of logical and quasi-logical language (“by the term ‘sun’ I will mean that object X, independent from any Y, orbited by planets f, g, h, … , i, that has the property P of being yellow, etc.”), as well as an occasional descent into a scholastic investigation of pedantic trees at the expense of more interesting philosophical forests. I will do my best to emphasize the useful features of analytic philosophy and to minimize the annoying and the useless!
With that stated, it should be noted that there are other ways to approach this subject matter. One is to take what is broadly termed a “phenomenological” approach, one inspired by the work of Husserl in the early twentieth century, and work of such thinkers as Merleau-Ponty, Heidegger, Sartre, among others. While there is no easy classification of these works, they all lean to some extent on what is known as the “phenomenological method,” rooted in Husserl's philosophy. Such an approach tries to “bracket” off any presuppositions about what we are in contact with in experience and to lay out just the “things” of experience themselves. What is found there and what happens next, philosophically speaking, differs greatly even among those committed to phenomenology. I will not be directly addressing this approach. This is as much for reasons of focus as anything else, and I by no means think that the phenomenological and analytic approaches must be in conflict. I see them, when done with care, as aiming at the same questions and even agreeing on much of what must be explained, even if connecting the two “camps” is not always easy. An excellent attempt to bring the two sides together is Shaun Gallagher and Dan Zahavi's The Phenomenological Mind. And the work of the late Francisco Varela did much to show how phenomenology and neuroscience might be usefully combined (see Varela 1996).
Further, I am not taking a distinctively neuroscientific approach to the problem of consciousness, though I will spell out some key spots where neuroscience and philosophy directly intersect. Again, this is certainly not because I think the philosophical questions are fully independent of questions in neuroscience, nor do I think neuroscience cannot alter the way philosophical issues are framed and resolved. On the contrary! But for reasons of focus, I will not even attempt to scratch the surface of the huge and ever-expanding neuroscientific literature on the conscious brain, except as it directly relates to the philosophical theories of consciousness presented herein. For an introduction to consciousness with a more neuroscientific approach, see Antti Revonsuo's Consciousness: The Science of Subjectivity. See also the wonderful popular works by neuroscientists Antonio Damasio, Joseph LeDoux, Michael Gazzaniga, and others. The interface between science and philosophy is extremely fluid when it comes to this topic. I hope that the current work will allow readers to usefully frame scientific results in light of philosophical controversies. And I hope the reader will still have time for minor things like eating and sleeping as well. There is just too much good stuff to read in this area, I'm afraid!
With that clarified, we can now consider some key distinctions that will pop up in the book. It is important to keep in mind that we use the word “consciousness” (and “conscious”) in a number of different ways. It's vital to be clear about what we mean. Sometimes we use the word “consciousness” to say something about creatures. We say, “The patient is unconscious,” or “Has the leopard regained consciousness yet?” In doing so, we are saying whether the creature is awake or unresponsive. When we get hit over the head with a tire iron, we lose consciousness in this sense. We can call this use of the word creature consciousness. But we also use the word to distinguish between our mental states. Some states are conscious and some are not. For example, I am currently in a conscious state of seeing my computer in front of me and of feeling my fingers as they type. But some of my states are not conscious (at least not until I mention them): my beliefs about the history of England, my desire for a new guitar, and so on. And I arguably even have nonconscious sensory states, like the state of feeling my rear end in my chair. Once I attend to it, the state becomes conscious, but before that, I keep track of my position on the chair and the pressures on my limbs nonconsciously. So some mental states are conscious and some are not. We can call this use of the word state consciousness.3
While there are some interesting exceptions, in this book we will be mainly interested in state consciousness. We want to know what has to be added to a mental state to make it a conscious state. We want to know if the special features that mark off conscious states from nonconscious ones are features that can be explained in physical, scientific terms. Creature consciousness, as I've defined it, is more of a basic biological function, that of being awake rather than completely unresponsive. And while we might wonder if a creature can really be creature conscious if none of its states are conscious, the real problem is about the states themselves. This is not to say, of course, that there aren't deep and fascinating questions about creature consciousness, notably surrounding the issue of persistent vegetative states and coma, but they are not the focus of our work here.
Another point about the word “consciousness” as we'll be using it in this book: the kind of consciousness that allegedly causes the problems we're interested in is sometimes called phenomenal consciousness in philosophy. Phenomenal consciousness is the sort of consciousness that occurs when there's “something it's like to be you – for you,” to paraphrase philosopher Thomas Nagel. Some philosophers argue that phenomenal consciousness is really some easier-understood thing, while others hold that it is a special and unique phenomenon. We need to be neutral in our use of the term. All I mean by “phenomenal consciousness” is the sort of conscious experience marked by qualities like redness or painfulness, the consciousness causing the worries we touched on above. By using the term, I don't mean to endorse the idea that phenomenal consciousness is unique and special, nor do I wish to deny it. Like many technical terms in philosophy, a lot is built into the usage, so we must be careful. But because “phenomenal consciousness” has become widely used as the term picking out the thing all the fighting is about, I'll follow the herd and use it as well. So sometimes I'll say “consciousness,” other times “phenomenal consciousness,” and even things like “phenomenal experience.” I mean the same thing by all of them: the kind of consciousness there's something it's like for the subject to experience, the consciousness that keeps philosophers up at night.
We also need to say a few preliminary words about what it means to say “everything is physical” or “consciousness is nothing more than a physical process,” or “phenomenal properties are just physical properties” and so on. One way to think of the problem of consciousness is via the question of how consciousness could just be a process like digestion or respiration or perspiration. These biological processes, though there are still some things we don't know about them, seem to fit right into the scientific view that everything happening in the universe is ultimately a process involving the basic forces of nuclear attraction, electromagnetism, and gravity, in various combinations. Digestion is a process by which food is broken down into usable energy for the body. This is a chemical process: complex starches, say, are converted into the glucose our cells need to power their activities. And the chemistry is explainable in terms of more basic atomic interactions: various attractions and repulsions at the atomic level make up chemical reactions. There's nothing else to them in the final analysis. And likewise for respiration, which is a transfer of gases between body and world. And for perspiration, the release of water onto the skin, which then cools the body by evaporation. All these things are chemical processes, and the chemical processes are themselves nothing more than atomic physical processes.
The idea that everything in the universe is nothing more than these sorts of physical processes is called physicalism. Philosophers have given more precise formulations of the idea, but this gives us the basic flavor.4 The big question about consciousness is: is it nothing more than a physical process in the same way that digestion, respiration, and perspiration are nothing more than physical processes? Another term used by philosophers to capture this question is “supervene.” If one thing supervenes on another, then that thing is nothing over and above the thing it supervenes on. Another way of putting it is to say that if A supervenes on B, there can be no change in A without a change in B. Mountains, for example, are nothing over and above huge clumps of atoms in the right locations. When God was making mountains, all he had to do was put some huge clumps of atoms in the right places. He didn't have to do anything else once he had the atoms in place – he didn't have to add any “magic mountain dust” to transform those huge lumps of atoms into mountains. All there is to mountains is huge clumps of properly arranged atoms. So we say mountains supervene on huge clumps of atoms. They are nothing above and beyond that. Now, the question about consciousness becomes: does consciousness supervene
