Kinds Of Minds

Toward An Understanding Of Consciousness


By Daniel C. Dennett

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Combining ideas from philosophy, artificial intelligence, and neurobiology, Daniel Dennett leads the reader on a fascinating journey of inquiry, exploring such intriguing possibilities as: Can any of us really know what is going on in someone else’s mind? What distinguishes the human mind from the minds of animals, especially those capable of complex behavior? If such animals, for instance, were magically given the power of language, would their communities evolve an intelligence as subtly discriminating as ours? Will robots, once they have been endowed with sensory systems like those that provide us with experience, ever exhibit the particular traits long thought to distinguish the human mind, including the ability to think about thinking? Dennett addresses these questions from an evolutionary perspective. Beginning with the macromolecules of DNA and RNA, the author shows how, step-by-step, animal life moved from the simple ability to respond to frequently recurring environmental conditions to much more powerful ways of beating the odds, ways of using patterns of past experience to predict the future in never-before-encountered situations. Whether talking about robots whose video-camera “eyes” give us the powerful illusion that “there is somebody in there” or asking us to consider whether spiders are just tiny robots mindlessly spinning their webs of elegant design, Dennett is a master at finding and posing questions sure to stimulate and even disturb.



Content and Consciousness
Elbow Room
The Intentional Stance
Consciousness Explained
Darwin’s Dangerous Idea


Toward an Understanding of Consciousness


A Member of the Perseus Books Group


I am a philosopher, not a scientist, and we philosophers are better at questions than answers. I haven’t begun by insulting myself and my discipline, in spite of first appearances. Finding better questions to ask, and breaking old habits and traditions of asking, is a very difficult part of the grand human project of understanding ourselves and our world. Philosophers can make a fine contribution to this investigation, exploiting their professionally honed talents as question critics, provided they keep an open mind and restrain themselves from trying to answer all the questions from “obvious” first principles. There are many ways of asking questions about different kinds of minds, and my way—the way I will introduce in this book—changes almost daily, getting refined and enlarged, corrected and revised, as I learn of new discoveries, new theories, new problems. I will introduce the set of fundamental assumptions that hold my way together and give it a stable and recognizable pattern, but the most exciting parts of this way are at the changeable fringes of the pattern, where the action is. The main point of this book is to present the questions I’m asking right now— and some of them will probably lead nowhere, so let the reader beware. But my way of asking questions has a pretty good track record over the years, evolving quite smoothly to incorporate new discoveries, some of which were provoked by my earlier questions. Other philosophers have offered rival ways of asking the questions about minds, but the most influential of these ways, in spite of their initial attractiveness, lead to self-contradictions, quandaries, or blank walls of mystery, as I will demonstrate. So it is with confidence that I recommend my current candidates for the good questions.

Our minds are complex fabrics, woven from many different strands and incorporating many different designs. Some of these elements are as old as life itself, and others are as new as today’s technology. Our minds are just like the minds of other animals in many respects and utterly unlike them in others. An evolutionary perspective can help us see how and why these elements of minds came to take on the shapes they have, but no single straight run through time, “from microbes to man,” will reveal the moment of arrival of each new thread. So in what follows I have had to weave back and forth between simple and complex minds, reaching back again and again for themes that must be added, until eventually we arrive at something that is recognizably a human mind. Then we can look back, one more time, to survey the differences encountered and assess some of their implications.

Early drafts of this book were presented as the Agnes Cuming Lectures at University College, Dublin, and in my public lectures as Erskine Fellow at Canterbury University, Christchurch, New Zealand, in May and June of 1995.1 want to thank the faculty and students at those institutions, whose constructive discussions helped make the final draft almost unrecognizably different, and (I trust) better. I also want to thank Marc Hauser, Alva Noe, Wei Cui, Shannon Densmore, Tom Schuman, Pascal Buckley, Jerry Lyons, Sara Lippincott, and my students in “Language and Mind” at Tufts, who read and vigorously criticized the penultimate draft.

Tufts University
December 20, 1995



Can we ever really know what is going on in someone else’s mind? Can a woman ever know what it is like to be a man? What experiences does a baby have during childbirth? What experiences, if any, does a fetus have in its mother’s womb? And what of nonhuman minds? What do horses think about? Why aren’t vultures nauseated by the rotting carcasses they eat? When a fish has a hook sticking through its lip, does it hurt the fish as much as it would hurt you, if you had a hook sticking through your lip? Can spiders think, or are they just tiny robots, mindlessly making their elegant webs? For that matter, why couldn’t a robot—if it was fancy enough—be conscious? There are robots that can move around and manipulate things almost as adeptly as spiders; could a more complicated robot feel pain, and worry about its future, the way a person can? Or is there some unbridgeable chasm separating the robots (and maybe the spiders and insects and other “clever” but mindless creatures) from those animals that have minds? Could it be that all animals except human beings are really mindless robots? René Descartes notoriously maintained this in the seventeenth century. Might he have been dead wrong? Could it be that all animals, and even plants—and even bacteria—have minds?

Or, to swing to the other extreme, are we so sure that all human beings have minds? Maybe (to take the most extreme case of all) you’re the only mind in the universe; maybe everything else, including the apparent author of this book, is a mere mindless machine. This strange idea first occurred to me when I was a young child, and perhaps it did to you as well. Roughly a third of my students claim that they, too, invented it on their own and mulled it over when they were children. They are often amused to learn that it’s such a common philosophical hypothesis that it has a name—solipsism (from Latin for “myself alone”). Nobody ever takes solipsism seriously for long, as far as we know, but it does raise an important challenge: if we know that solipsism is silly—if we know that there are other minds—how do we know?

What kinds of minds are there? And how do we know? The first question is about what exists—about ontology, in philosophical parlance; the second question is about our knowledge—about epistemology. The goal of this book is not to answer these two questions once and for all, but rather to show why these questions have to be answered together. Philosophers often warn against confusing ontological questions with epistemological questions. What exists is one thing, they say, and what we can know about it is something else. There may be things that are completely unknowable to us, so we must be careful not to treat the limits of our knowledge as sure guides to the limits of what there is. I agree that this is good general advice, but I will argue that we already know enough about minds to know that one of the things that makes them different from everything else in the universe is the way we know about them. For instance, you know you have a mind and you know you have a brain, but these are different kinds of knowledge. You know you have a brain the way you know you have a spleen: by hearsay. You’ve never seen your spleen or your brain (I would bet), but since the textbooks tell you that all normal human beings have one of each, you conclude that you almost certainly have one of each as well. You are more intimately acquainted with your mind—so intimately that you might even say that you are your mind. (That’s what Descartes said: he said he was a mind, a res cogitans, or thinking thing.) A book or a teacher might tell you what a mind is, but you wouldn’t have to take anybody’s word for the claim that you had one. If it occurred to you to wonder whether you were normal and had a mind as other people do, you would immediately realize, as Descartes pointed out, that your very wondering this wonder demonstrated beyond all doubt that you did indeed have a mind.

This suggests that each of us knows exactly one mind from the inside, and no two of us know the same mind from the inside. No other kind of thing is known about in that way. And yet this whole discussion so far has been conducted in terms of how we know—you and I. It presupposes that solipsism is false. The more we—we—reflect on this presupposition, the more unavoidable it appears. There couldn’t be just one mind—or at least not just one mind like our minds.


If we want to consider the question of whether nonhuman animals have minds, we have to start by asking whether they have minds in some regards like ours, since these are the only minds we know anything about—at this point. (Try asking yourself whether nonhuman animals have flurbs. You can’t even know what the question is, if you don’t know what a flurb is supposed to be. Whatever else a mind is, it is supposed to be something like our minds; otherwise we wouldn’t call it a mind.) So our minds, the only minds we know from the outset, are the standard with which we must begin. Without this agreement, we’ll just be fooling ourselves, talking rubbish without knowing it.

When I address you, I include us both in the class of mind-havers. This unavoidable starting point creates, or acknowledges, an in-group, a class of privileged characters, set off against everything else in the universe. This is almost too obvious to notice, so deeply enshrined is it in our thinking and talking, but I must dwell on it. When there’s a we, you are not alone; solipsism is false; there’s company present. This comes out particularly clearly if we consider some curious variations:

“We left Houston at dawn, headin’ down the road—just me and my truck.”

Strange. If this fellow thinks his truck is such a worthy companion that it deserves shelter under the umbrella of “we,” he must be very lonely. Either that, or his truck must have been customized in ways that would be the envy of roboticists everywhere. In contrast, “we—just me and my dog” doesn’t startle us at all, but “we—just me and my oyster” is hard to take seriously. In other words, we’re pretty sure that dogs have minds, and we’re dubious that oysters do.

Membership in the class of things that have minds provides an all-important guarantee: the guarantee of a certain sort of moral standing. Only mind-havers can care; only mind-havers can mind what happens. If I do something to you that you don’t want me to do, this has moral significance. It matters, because it matters to you. It may not matter much, or your interests may be overridden for all sorts of reasons, or (if I’m punishing you justly for a misdeed of yours) the fact that you care may actually count in favor of my deed. In any event, your caring automatically counts for something in the moral equation. If flowers have minds, then what we do to flowers can matter to them, and not just to those who care about what happens to flowers. If nobody cares, then it doesn’t matter what happens to flowers.

There are some who would disagree; they would insist that the flowers had some moral standing even if nothing with a mind knew of or cared about their existence. Their beauty, for instance, no matter how unappreciated, is a good thing in itself, and hence should not be destroyed, other things being equal. This is not the view that the beauty of these flowers matters to God, for instance, or that it might matter to some being whose presence is undetectable by us. It is the view that the beauty matters, even though it matters to no one—not to the flowers themselves and not to God or anybody else. I remain unpersuaded, but rather than dismiss this view outright I will note that it is controversial and not widely shared. In contrast, it takes no special pleading at all to get most people to agree that something with a mind has interests that matter. That’s why people are so concerned, morally, about the question of what has a mind: any proposed adjustment in the boundary of the class of mind-havers has major ethical significance.

We might make mistakes. We might endow mindless things with minds, or we might ignore a mindful thing in our midst. These mistakes would not be equal. To overattribute minds—to “make friends with” your houseplants or lie awake at night worrying about the welfare of the computer asleep on your desk—is, at worst, a silly error of credulity. To underattribute minds—to disregard or discount or deny the experience, the suffering and joy, the thwarted ambitions and frustrated desires of a mind-having person or animal—would be a terrible sin. After all, how would you feel if you were treated as an inanimate object? (Notice how this rhetorical question appeals to our shared status as mind-havers.)

In fact, both errors could have serious moral consequences. If we over attributed minds (if, for instance, we got it into our heads that since bacteria had minds, we couldn’t justify killing them), this might lead us to sacrifice the interests of many legitimate interest-holders—our friends, our pets, ourselves—for nothing of genuine moral importance. The abortion debate hinges on just such a quandary; some think it’s obvious that a ten-week-old fetus has a mind, and others think it’s obvious that it does not. If it does not, then the path is open to argue that it has no more interests than, say, a gangrenous leg or an abscessed tooth—it can be destroyed to save the life (or just to suit the interests) of the mind-haver of which it is a part. If it does already have a mind, then, whatever we decide, we obviously have to consider its interests along with the interests of its temporary host. In between these extreme positions lies the real quandary: the fetus will soon develop a mind if left undisturbed, so when do we start counting its prospective interests? The relevance of mind-having to the question of moral standing is especially clear in these cases, since if the fetus in question is known to be anencephalic (lacking a brain), this dramatically changes the issue for most people. Not for all. (I am not attempting to settle these moral issues here, but just to show how a common moral opinion amplifies our interest in these questions way beyond normal curiosity.)

The dictates of morality and scientific method pull in opposite directions here. The ethical course is to err on the side of overattribution, just to be safe. The scientific course is to put the burden of proof on the attribution. As a scientist, you can’t just declare, for instance, that the presence of glutamate molecules (a basic neurotransmitter involved in signaling between nerve cells) amounts to the presence of mind; you have to prove it, against a background in which the “null hypothesis” is that mind is not present. [Innocent until proven guilty is the null hypothesis in our criminal law.) There is substantial disagreement among scientists about which species have what sorts of mind, but even those scientists who are the most ardent champions of consciousness in animals accept this burden of proof—and think they can meet it, by devising and confirming theories that show which animals are conscious. But no such theories are yet confirmed, and in the meantime we can appreciate the discomfort of those who see this agnostic, wait-and-see policy as jeopardizing the moral status of creatures they are sure are conscious.

Suppose the question before us were not about the minds of pigeons or bats but about the minds of left-handed people or people with red hair. We would be deeply offended to be told that it had yet to be proved that this category of living thing had the wherewithal for entry into the privileged class of mind-havers. Many people are similarly outraged by the demand for proof of mind-having in nonhuman species, but if they’re honest with themselves they will grant that they, too, see the need for such proof in the case of, say, jellyfish or amoebas or daisies; so we agree on the principle, and they’re just taking umbrage at its application to creatures so very much like us. We can allay their misgivings somewhat by agreeing that we should err well on the side of inclusive-ness in all our policies, until the facts are in; still, the price you must pay for scientific confirmation of your favorite hypothesis about animal minds is the risk of scientific disconfirmation.


It is beyond serious dispute, however, that you and I each have a mind. How do I know you have a mind? Because anybody who can understand my words is automatically addressed by my pronoun “you,” and only things with minds can understand. There are computer-driven devices that can read books for the blind: they convert a page of visible text into a stream of audible words, but they don’t understand the words they read and hence are not addressed by any “you” they encounter; it passes right through them and addresses whoever listens to—and understands—the stream of spoken words. That’s how I know that you, gentle reader/listener, have a mind. So do I. Take my word for it.

In fact that’s what we routinely do: we take each other’s words as settling beyond any reasonable doubt the question of whether we each have minds. Why should words be so convincing? Because they are such powerful resolvers of doubts and ambiguities. You see somebody coming toward you, scowling and waving an ax. You wonder, What’s his problem? Is he going to attack me? Is he mistaking me for somebody else? Ask him. Perhaps he will confirm your worst fears, or perhaps he will tell you he has given up trying to unlock his car (which you’re standing in front of) and has returned with his ax to break the window. You may not believe him when he says it’s his car, not somebody else’s, but further conversation—if you decide not to run away—is bound to resolve your doubts and clarify the situation in ways that would be all but impossible if you and he were unable to communicate verbally. Suppose you try asking him, but it turns out that he doesn’t speak your language. Perhaps you will then both resort to gestures and miming. These techniques, used with ingenuity, will take you far, but they’re a poor substitute for language—just reflect on how eagerly you would both seek to confirm your hard-won understanding if a bilingual interpreter were to come along. A few relayed questions and answers would not just allay any residual uncertainty but would add details that could not be conveyed in any other way: “When he saw you put one hand on your chest and push out with your other hand, he thought you meant that you were ill; he was trying to ask if you wanted him to take you to a doctor once he’d broken the window and retrieved his keys. That business with his fingers in his ears was his attempt to convey a stethoscope.” Ah, it all falls into place now, thanks to a few words.

People often emphasize the difficulty of accurate and reliable translation between human languages. Human cultures, we are told, are too different, too “incommensurable,” to permit the meanings available to one speaker to be perfectly shared with another. No doubt translation always falls somewhat short of perfection, but this may not matter much in the larger scheme of things. Perfect translation may be impossible, but good translation is achieved every day—routinely, in fact. Good translation can be objectively distinguished from not-so-good translation and from bad translation, and it permits all human beings, regardless of race, culture, age, gender, or experience, to unite more closely with one another than individuals of any other species can. We human beings share a subjective world—and know that we do—in a way that is entirely beyond the capacities of any other creatures on the planet, because we can talk to one another. Human beings who don’t (yet) have a language in which to communicate are the exception, and that’s why we have a particular problem figuring out what it’s like to be a newborn baby or a deaf-mute.

Conversation unites us. We can all know a great deal about what it’s like to be a Norwegian fisherman or a Nigerian taxi driver, an eighty-year-old nun or a five-year-old boy blind from birth, a chess master or a prostitute or a fighter pilot. We can know much more about these topics than we can know about what it’s like (if anything) to be a dolphin, a bat, or even a chimpanzee. No matter how different from one another we people are, scattered around the globe, we can explore our differences and communicate about them. No matter how similar to one another wildebeests are, standing shoulder to shoulder in a herd, they cannot know much of anything about their similarities, let alone their differences. They cannot compare notes. They can have similar experiences, side by side, but they really cannot share experiences the way we do.

Some of you may doubt this. Can’t animals “instinctively” understand each other in ways we human beings cannot fathom? Certainly some authors have said so. Consider, for instance, Elizabeth Marshall Thomas, who imagines, in The Hidden Life of Dogs (1993), that dogs enjoy a wise understanding of their own ways. One example: “For reasons known to dogs but not to us, many dog mothers won’t mate with their sons.” (p. 76). Their instinctive resistance to such inbreeding is not in doubt, but what gives her the idea that dogs have any more insight into the reasons for their instincts than we have into ours? There are many things we feel strongly and instinctively disinclined to do, with no inkling about why we feel that way. To suppose without proof that dogs have more insight into their urges than we do is to ignore the null hypothesis in an unacceptable way—if we are asking a scientific question. As we shall see, very simple organisms may be attuned to their environments and to each other in strikingly apt ways without having the slightest appreciation of their attunement. We already know from conversation, however, that people are typically capable of a very high order of understanding of themselves and others.

Of course, we can be fooled. People often emphasize the difficulty of determining whether a speaker is sincere. Words, by being the most powerful tools of communication, are also the most powerful tools of deception and manipulation. But while it may be easy to lie, it’s almost as easy to catch a liar—especially when the lies get large and the logistical problem of maintaining the structure of falsehood overwhelms the liar. In fantasy, we can conjure up infinitely powerful deceivers, but the deceptions that are “possible in principle” to such an evil demon can be safely ignored in the real world. It would be just too difficult to make up that much falsehood and maintain it consistently. We know that people the world over have much the same likes and dislikes, hopes and fears. We know that they enjoy recollecting favorite events in their lives. We know that they all have rich episodes of waking fantasy, in which they rearrange and revise the details deliberately. We know that they have obsessions, nightmares, and hallucinations. We know that they can be reminded by an aroma or a melody of a specific event in their lives, and that they often talk to themselves silently, without moving their lips. Long before there was scientific psychology, long before there was meticulous observation of and experimentation on human subjects, this was all common knowledge. We have known these facts about people since ancient times, because we have talked it over with them, at great length. We know nothing comparable about the mental lives of any other species, because we can’t talk it over with them. We may think we know, but it takes scientific investigation to confirm or refute our traditional hunches.


It’s very hard to tell what somebody is thinking who won’t discuss it—or who can’t, for one reason or another. But we normally suppose that such incommunicative folks are indeed thinking—that they do have minds—even if we can’t confirm the details. This much is obvious, if only because we can readily imagine ourselves in a situation in which we would steadfastly refuse to communicate, all the while thinking our private thoughts, perhaps reflecting with amusement on the difficulties that observers were having in figuring out what, if anything, was going on in our minds. Talking, no matter how conclusive its presence may be, is not necessary for having a mind. From this obvious fact we are tempted to draw a problematic conclusion: there could be entities who do have minds but who cannot tell us what they’re thinking—not because they’re paralyzed or suffering from aphasia (the inability to communicate verbally due to localized brain damage), but because they have no capacity for language at all. Why do I say this is a problematic conclusion?


On Sale
Aug 4, 2008
Page Count
192 pages
Basic Books

Daniel C. Dennett

About the Author

Daniel C. Dennett is Distinguished Arts and Sciences Professor, Professor of Philosophy, and Director of the Center for Cognitive Studies at Tufts University.

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