Interview with Daniel C. Dennett
May ‘10

The Moscow Center for Consciousness Studies arranged an interview with Daniel C. Dennett on March 5, 2010. The interview was conducted by Vadim Vasilyev and Dmitry Volkov.

Download the interview with Daniel Dennett you can here .

05/03/2010 The interview participants: Mr.Dennett, Mr.Vasilyev, Mr.Volkov

DV: The first question we would like to ask you concerns the history of philosophy. What do you think of the great philosophers of the past, and do you think there is any use for their theories in contemporary philosophy?

DD: It is a good question. I think, yes, there is. Philosophy, more than other disciplines, must include a large element of historical scholarship for a very simple reason. Philosophy, in large measure, is a history of very tempting mistakes. The great philosophers were no fools. They got a lot of things right, and they got a lot of things wrong. If you do not know the history of philosophy, you are almost certain to make the same mistakes they made. I take great delight in watching, for instance, scientists who do not know any philosophy trying to figure out the mind. And with clock-like precision they repeat the mistakes of Hume and Kant and Aristotle. It is just stunning to see how tempting these ideas are. And the only way you can learn that they are not quite right is by learning the history of the field.

VV: Recently you said that Hume is your favorite philosopher. Why is it so?

DD: Maybe it is his candor. He is so open minded. He expresses himself so openly. So many philosophers seem to be going out of their own way to talk fancier, to seem a little bit mysterious or obscure, difficult. But Hume seems to be trying to get you to understand. He is trying to understand himself. He is also just so smart. He had great insights, I think, into many topics. He was quite revolutionary in his ideas about causation and his ideas about the self. He was also such an optimistic and happy emotional spirit. I just love his personality. If I were to have a dinner party in Heaven with a few philosophers, Hume would be the first guest on my list. I do not know whether we would talk about philosophy, but we would have a good time!


VV: He was an armchair philosopher, wasn’t he? He didn’t like experiments too much.

DD: Yes, those were the early days. Look at the other empiricists, Locke and Berkeley and Reid, for instance. They were very knowledgeable about the science of their day. But they did not actually do experiments, to be sure. The idea of philosophers doing experiments is a fairly recent one. Although, one has to say that certainly Descartes did experiments because he was not just a philosopher, he was also a scientist. But I think that Hume thought that he had found a method of doing philosophy that was a sort of an experimental method. It was a forerunner in a certain sense of phenomenology.

VV: OK, but what makes a good philosopher?

DD: I think it changes with the time. I think today you can not really be a good philosopher if you are just a philosopher. If all one knows is philosophy, then you are working in an atmosphere that is too thin, too rarified, you are too high in altitude, and you should get down closer to the ground. And you should learn about other fields, should they be politics, history, or neuroscience. It might be mathematics or physics or the arts. But I think that the role of the pure armchair metaphysician is very limited. And almost nothing that is done in that tradition is worth doing, I think.

DV: This brings us to the next question. What is the difference between science and philosophy? Do you think that there is actually a reason for a separate discipline to exist? Is there a reason to have people who call themselves philosophers? Maybe it is better to have scientists that look up and study more abstract notions or concepts?

DD: It is an interesting idea, Dmitriy. You may be right. For the moment, at least, I think, it is probably better for philosophers, whatever other area they look into, to have a sort of common background of training. Because you never can tell when some arguments arise. Let us be extreme. Some arguments in ethics arise that may cast an interesting shadow onto work on philosophy of science or neuroscience. There is something to the training of a philosopher in understanding argument and analysis of argument that is general. I have a number of very fine graduate students who have even PhDs in other fields and sciences. They then go into philosophy and seem to learn a great deal. They do not always enjoy learning it. But they learn a great deal from taking courses quite outside of their conceptual interests because of their ways of thinking that they learn them.

VV: What do you think about a new field of experimental philosophy?

DD: I am cautiously optimistic about it. I think like in any new field, there is a lot of junk work that is being done. And only the best of it is worth doing. But there is some that is worth doing. And these are early days. And if they do not drown in the dark field this will be a good addition to the philosophical method.

VV: Are you an experimental philosopher?

DD: No. I have not rounded up any hundreds of undergraduates or other people to give questionnaires to, or done any of that. But I have talked closely with people doing this sort of work. And a few of my students have done some of this. But I have not posed an experimental question that I felt the need to test yet. In a sense, that is not true. When I was working on my religion project for “Breaking the spell”, we did in fact do some experimental work. It was not really experimental philosophy, although one might say it was. We looked at whether people could be provoked into stiffening their dogmas and religious beliefs by viewing the questionnaire as something of a challenge to them rather than as a friendly enquiry. So we posed questions to people. We had a scale of answers where we anticipated that if they felt their religious beliefs were being challenged at all by the question (some of the questions were a little pointed), that this would stiffen their backs and they would answer with a more fundamentalists’ answer. They would respond to this faintly felt challenge with, shall we say, more aggressive or more dogmatic answers. We would find a little of that effect, but it was not significant. We did not design the experiment well, so it was back to the drawing board. It is hard to do this well. And one way to learn how hard is, is to try, which I did. We devoted a lot of effort to different questionnaires that we used. And we received hundreds of responses, but no publishable results came from it.

DV: Do you think that any of your important ideas about what consciousness is can be tested?

DD: Oh, yes, certainly. Some of them in effect are being tested. It has been now 20 years since I published “Consciousness Explained”. The idea of multiple draft models, or the fame in the brain mode, has had a good run. And numbers of experiments have been done that are certainly consistent with it. Nothing has come up that I think seriously challenges the basic idea there. There had been some experiments that wanted to challenge it, but didn’t come up with anything good. The whole area of change blindness in a sense grew out of some of the claims I made in “Consciousness Explained”. That is certainly fruitful.

VV: Going back to experimental philosophy, if you are not an experimental philosopher in a strict sense, how would you describe your own philosophy? What is it like?

DD: Well, I think the best way to understand my philosophy is to see how it evolved, the history of it. When I was a graduate student I became interested in the mind, and how the mind could be the brain, how the brain could be the mind, and just how learning could happen. The idea of the brain as a self redesigning entity and how it would be possible to have a non-miraculous account of learning in the brain. That led me to my hypothesis about it being an evolutionary process in the brain. And that led me to evolution and evolutionary biology which I had never studied before. If you go back and look at my first book “Content and Consciousness” you can see that the ideas, the themes of my whole life’s work, were pretty well articulated in that book. I think what happened was that I just found some good questions to ask. That’s the key to philosophy. I found some questions that were really fruitful. And I have just been turning the crank, and answering those questions and proving the answers ever since. So it was content first, then consciousness. A lot of philosophers of course have thought that, no, you have to do the consciousness first. But I think that is a mistake on several levels. I think you should get a good foundational theory of intentionality, of intentional content, of the semantic content in the brain, and then you can build consciousness on top of that. Of course, I discovered that a lot of the resistance to my way of thinking, and sometimes it was veiled, it was not well articulated, it was sort of tacit or implicit in what was said, grew out a fear about free will. The fear that we do not have free will, that science might show that we do not have free will. That this was really the driving force, this was what motivated people at the end of the day to do whatever they were doing. So that led to two books. First “Elbow Room” and then “Freedom Evolves”. The same theory is presented in both of them though much more articulated in a later book. So, I would say that what has driven me all along is the idea that the problems of the mind, which are already conceptually difficult, are made more difficult by people’s anxieties about two things: about free will and God. People have grown up with the idea of the immortal soul, and the idea that ethics depends on having a soul, and on there being a God. And when you start to attack that assumption by saying “No, we do not have an immortal soul, there is no miracle going on here, it is just the brain”, this strikes people with anxiety and animosity. And a lot of the work that has been done both by philosophers and by scientists has been distorted by this hidden agenda. I was so glad that I wrote “Elbow Room” when I did. Because after I wrote “Consciousness Explained” and published it, people came up to me again and again and said “…that is all very well, very interesting… but what about free will?” I would say “It is a good question. I have already written a book on that subject which should answer your questions. You are right, that is a big problem, what about free will?” So, I had already my answer ready for them, but of course I had to do it again.

DV: It is clear that your philosophy was concentrated on intentionality and on consciousness, and then you addressed important questions, the free will and religion. Will you call your philosophy a system?

DD: That is a pretty fancy word. No, I think that it holds together pretty well for the reasons I have just stated because of the way it grew. But it was never a system in the sense that I thought I had a methodology that had these great, strict principles and you just follow them through and you teach it to others or something like that. So I had not had an “ism”. It is not like Husserl’s phenomenology with a capital “P”. It is not like that.

DV: Speaking about the structure, where is the boundary between different parts of your philosophy as a whole?

DD: Well, I think if I have done it right, the borders, the boundaries should be permeable and uncertain because everything should lead to the next thing. If it goes well, then anything I say about free will or ethics should flow out from what I have just said about consciousness, the limitations of the brain, and the evolution of the mind. And certainly everything I have decided about religion has certainly grown very directly out of my thinking about cultural evolution in the mind and psychology. I think compartmentalization is only really useful when you have to teach a course and have to tell the students “This course is going to be about cultural evolution, this course is going to be about free will or about consciousness.” This concentrates the topic but will have leakage from the other areas

VV: But if you are going to teach a course about your own philosophy, which part will you begin with?

DD: I think I would begin with intentional systems and intentional stance and understanding of biology. Actually my little book “Kinds of Minds” might be a good place to begin.

VV: It has been translated into Russian. Do you know about that?

DD: Really? I have seen other editions in other languages, but not one in Russian. Will you find a copy for my collection? I have no interest in pursuing the legalities of it. I just would like to have a copy.

VV: Was there something that radically changed you mind?

DD: I do not know how radical it is, but just in the last couple of years I [reconsidered] one of the lines that I took on homoncular functionalism and the breakdown of the mind into parts that were intentional systems until we finally get down to the parts that can be replaced by a machine. And for years I had been thinking of the parts as being more like a neuron, and a neuron being just a switch. In my first book, “Content and Consciousness”, I have a diagram with a McCulloch pits logical neuron, I knew at that time it was a simplification. But I thought it would do for the time being. Well I since decided that, no, neurons, individual neurons, are actually pretty clever. And that they have their own agendas. There really are intentional systems in a strong sense. You won’t understand the brain as being a huge community of only partially cooperative agents that are trapped in the scull. And they are always looking for work, because they must stay alive. And are always looking for ways to improve their circumstances. And that although this at first looks very fanciful, the idea of the brain teeming with agents, it is not until you recognize that every neuron in your brain is a direct descendant of free-living, free-swimming, unicellular, eukaryotic cells, and took care of themselves in the ocean for a billion years. So they had plenty of time to pick up lots of competence to protect themselves and to discriminate circumstances that were good and bad. I do not think they have lost all their powers by being incorporated into multi-cellular organism’s brains. I think that the brain, in fact, can be considered an arena in which they get to vie with each other very competitively for influence. Of course, in a way this just grows out of some of the things I have said about competition in the brain in “Consciousness Explained”. But I have seen that I want to take this competitive angle much more literally than I sometimes thought in the past. I thought it was competitive, but in a sort of friendly tug-of-war spirit. But now they look to me to be not so friendly.

VV: How did you realize that?

DD: There are a couple of things that motivated me. One of them came while I was reading a wonderful book by George Ainslie “The Breakdown of Will”. I think it is a marvelous book, full of insights, very original. But I became puzzled about how there could be warring interests in the brain. And if we get neuro-scientific about this and asked people what if, say, dopamine, for instance, were to be the currency of reward. One thinks that this as a currency can not be literal. If it is currency, what will they buy with it? What do you buy with the currency of dopamine? If they are not buying something with it then what is the point of the metaphor? I began to think, well, the only thing that makes sense to talk about currency as a reward is if you have consumers in there that are little agents of their own that have needs and projects and agendas. That may seem a bit fanciful at first. But the more I look, the more I thought maybe we should really take the idea seriously. Then my good friend Tecumseh Fitch published a piece called “Nano-Intentionality” in the “Journal of Biology and Philosophy”. And that piece reports to be largely very critical of my account of original and derived intentionality. He argues that the brain cell is the basic, the first level of original intentionality. And, although I do not like his use of the term “original intentionality” for that, and I think that dividing line between the pro and new eukaryotic cell is not as clear as he believes, he pushes the idea that neurons are remarkable little agents with the capacity to adjust their behavior to improve their circumstances across a wide variety of environments. And I think that is a key idea.

DV: It is very inspiring, the subject of different agents. In our phenomenology we understand our consciousness as something unified, something integrated. What makes the experience unified?

DD: I think that the sense of unity is not due to the transcendental unity of our existence. On the contrary, I think it is largely illusory. And I think that the unity that we ascent is indeed achieved when all is going well and we can go through weeks and months at a time seemingly very well unified. But that is an accomplishment, not a precondition for consciousness. And it can fall apart quite radically. The most dramatic and salient of course is something like multiple personality disorder or associative disorder. But there are cases much milder and more familiar. And less controversial, like all sorts of internal conflicts that we face. We talked about the easy decisions we make. They are, as we say in English, “no brainers”. Of course they’re brainers that don’t make a huge use of the brain. But think of the decisions that that are not “no brainers”. The ones that once we organize them we are distraught, and in despair. We worry and can not get to sleep thinking about these things. I think what is going on in these circumstances is a sort of internal war between factions of our brain. We are not as unified as we think we are. A lot of the unity that we display to our friends and to ourselves is a sort of superficial unity. And behind it lie lots of crosscurrents, lots of possibly dis-unified competences which express themselves when they can. If you start thinking this way, you will see that so many phenomena which are readily analyzable into temporary factional disputes that were factions that are normally suppressed are playing a bigger that unusual role, whether or not they come all the way up to consciousness.

DV: It is very interesting what you say. In your famous thought experiment “Where am I” you suggested an imaginary situation: one body and two brains – the computer brain and the organic brain. At first the two brains working synchronically, at the same time replicating each other and directing person’s behavior. And at some point they started going in different directions. I was a little bit surprising that in this thought experience you actually allowed one brain to notice the difference. You were just talking about the war that is continuously waged in our brain, and that unity is only illusory. But why do you expect that such a person will notice the difference. Why did you say that?

DD: There is a rather special circumstance in that there are two whole brains. There is a complete set of control organs and perceptual analyzers – that is a total duplication of the whole brain. Whereas in the sort of conflicts that I am talking about now, it is all within one brain. Its parts within that brain that are in conflict with each other. You’ll remember in the “Where Am I” story, when the brains get out of sync, one brain discovers that it simply has no control over its lips or its hands at all. There is nothing analogues to that which can be explained. Well, actually there is something a little bit analogous. There are such phenomena as the alien hand syndrome – which is quite rare. But in the alien hand syndrome, the sufferer sees the actions of his own hand as being under the control of some other agency. That is a very salient and extreme example. But if you are like me, you will have had a milder version of this on occasion where you suddenly find yourself saying: “Did I just say that what I heard myself say? How could I ever say that?” Right there, we see in everyday life a glimpse of the underlying possibilities of conflict. And of course there is lots of folklore about that and we shall say the Devil made us do it. Well, that is not entirely wrong! That is to say, that is a part of you which is by your current lights not as nice as the part you want to be. And that is the part of you that organized that particular action.

VV: Well. There is another question about the unity of consciousness. Is there any difference between your Multiple Drafts Model of consciousness and the Fame in the Brain model? Is there any difference between these models?

DD: The Fame in the Brain I think was just a better metaphor. Here’s what happened. When I wrote “Consciousness Explained” I wanted to destroy the Cartesian Theater idea which is so powerful. It still is a very, very seductive idea. I didn’t come up with a suitable alternative, a vivid and attractive and easy to remember alternative to the Cartesian Theater. But then shortly after the book was published, the Fame in the Brain idea occurred to me. I thought that was really better because I could contrast. The Cartesian Theater would have consciousness as sort of a medium, like what you get with television. But consciousness is not a communication medium. It is not a representational medium. It is rather a difference in influence, or a clout in the brain. That is what consciousness really is. It was important as a competing metaphor to show that there was an alternative to the otherwise very attractive idea that one thing happens in the brain, and then another thing happens in the brain, and then something else happens in the brain. And somewhere along the line suddenly you get a transduction into another medium and you have the glow of consciousness arriving. I think that is a very tempting idea. And it is just wrong.

VV: Is “Fame in the Brain” just a better metaphor?

DD: Yes, it is. It is just a better metaphor for the Multiple Drafts Model.

VV: Interesting. But in your “Sweet Dreams” (where the new metaphor was developed) you said that you were not as sure as earlier that the culture was so necessary for consciousness.

DD: Yes, I did. I guess that is the way you can read that. And in a sense, that is true. But let me go over that. The line between what is hardwired genetically and what is developmentally likely, even though not hardwired, and what is only developmentally likely under certain cultural circumstances, those are not strict lines. But in a thought experiment we can imagine exploring them in the following way. Do not try this at home, this is not an experiment you could ever do. Imagine raising a human baby in complete isolation – Robinson Crusoe as a baby on an island. No language, no social interactions, no cultural, no enculturation at all, but somehow nourished and able to get up and move around and locomote and so forth, not bedridden. So I think that the question then is what kind of consciousness would that entity, that organism, that human being have with no cultural input at all. First of all, of course, it is a horrible thing to even contemplate because there is very little doubt that it would be an extraordinarily disabled person. The empirical question is how strong are the genetically provided for dispositions; how much of the information and drive to develop the features of normal human consciousness would survive under that terrible circumstance and achieve their developmental results. Well, who knows? We do not know. But what I wanted to do was draw attention to the fact that we make a big mistake if we think that all of that competence, all of the thousands of dispositional habits that, at the computational level, compose our architecture of consciousness is in the brain. It is a big mistake to suppose that it is all genetically provided for. I think a great deal of it is provided by enculturation. In a way I am just making a sort of evo-devo point. It is not all just genes – developmental history is very important and it provides a lot of structure and a lot of information. A lot of the competence that we see in an adult is due to developmental processes. And those in turn are structured by culture because culture is a developmental environment that is hugely different. For instance, there are actually hundreds and hundreds of chimpanzees who were born in captivity and have spent their entire lives embedded in human culture in a certain sense. They have heard a lot of talk and their keepers have been their closest companions in effect. They have heard speech since the day they were born. They have grown up inside four walls with electric lights, hearing music and all the rest. They show no curiosity about language at all. It is just like the rustling of the leaves – they just do not attend to it. There is a tremendous amount of information in language that they are not attempting to process. This is completely unlike a human infant. Even a deaf human infant shows tremendous curiosity about communication in a language. There is a hunger for language. And that is genetic. So you have that hunger but that does not give you your consciousness. The hunger opens up the brain to all the developmental processes that language then shapes and feeds. And so you grow into your consciousness by learning a language. Consciousness is not just a language. The discipline of the brain that language imposes provides structures for the rest of the consciousness. It is in “Kinds of Minds” that I give the example of a chimpanzee imagining itself climbing up a rope with a wastebasket on its head. I deliberately chose the example because I wanted the image to be something imagined with familiar objects. It is not rocket science – the chimpanzee knows ropes, it knows plastic buckets. The question is could a chimpanzee imagine climbing a rope with a bucket on its head? Any child of four can readily imagine that. The chimpanzee has the same sense organs and the same familiarity with the objects and this is not a linguistic thing. It is sheer locomotory imagery. But is a chimpanzee actually capable of doing it? We do not know and it is hard to know how we could find out. What I am suggesting is that it is possible. It is an empirical possibility that the chimpanzee does not have the sort of functional spaces in its brain to permit this sort of imagination to go on. It does not have a free dealing imagination. It does not anymore than it has the capacity to hum melodies to itself. Now if that is true, then this would be an example of a structure, a functional structure in the chimpanzee’s brain that just did not exist, and did not exist because the chimpanzee was not enculturated.

VV: Once you said that people are zombies. Please explain are we really zombies after all?

DD: The whole idea of zombies is a manifest failure of imagination. And here is how it works. First we had the idea from the folklore of Haiti and other countries of voodoo, of zombies. This is the person who is the walking dead and you can tell them in a minute because they are sleep walking and they do not respond well to questions, they do not laugh at jokes, they know no fear, they are extraordinarily disabled but still they are able to get up and about. That is the voodoo zombie. And those in some sense are real. There is an interesting book on zombies and how to make them, how to drug people. But a philosophical zombie is not that at all. A philosophical zombie is somebody who’s behaviorally indistinguishable from a conscious, alive human being but its all darkness inside and there’s no consciousness going on. Now the idea that people know what they are imagining when they imagine this is stunning to me. And various philosophers who have looked at this say “Oh, I do not see any trouble. This is certainly conceivable”. Well I think they have a very impoverished view of conceivability if that is so. If that’s conceivable, then here is something else that is conceivable. An entity which looks atom for atom like a cat no matter how you study it – it purrs, it laps milk, it has cat DNA in all its cells, it stretches in the sun, but it is not alive. It is just an automaton cat. What on earth can the person be talking about? It is like vitalism, as if this is a cat that does not have any elan vital in its cells. I think if the zombie concept in philosophy should be taken seriously, then we should also take the cat zombie that is not alive seriously and say that biology has not yet tackled the hard problem of life. I do not see that one of those stories is any better than the other. I know that a lot of philosophers are unhappy with me because I heap scorn on this idea. And I say a philosopher should be embarrassed to take this seriously. It shows a certain frivolity and trivialness of philosophical imagination. But that is what I think. This is a demonstrably bad idea. The fact that so many philosophers want to go on taking it seriously I view that as an interesting sociological phenomenon. The reason they want to take it seriously is that it gives them something like a toy to play with and if they do not have that toy they do not know what to do. A lot of philosophers go into philosophy of mind because they are basically yearning dualists. They would like dualism to be true. They do not like the imperialism of science coming in and encroaching on their playground. The idea of the zombie is a plaything to engage their attention and energy that the scientists will have nothing to do with. Unfortunately sometimes scientists misunderstand what is going on and then they start taking zombies seriously. Christoff Koch, for example. But this concept of a zombie is not a philosopher’s concept. This concept of a zombie is much more like my concept of a neuron as an intelligent agent –not a conscious agent but as an intelligent agent.

VV: Why is it such a bad idea? Let us suppose, for example, that you imagine I have no mental images at all. Why not? I can imagine that you have no mental images. If so, I can imagine that you are a zombie.

DD: I can imagine that you are deaf or blind, or deaf and blind, or deaf and blind and numb, or deaf and blind and anomic – you have no sense of smell or taste. I can subtract perceptual senses from you and of course I can imagine you and I can think about what it is like to be lacking that. And in fact if you do lack one of these, you can tell me. I can also well imagine that you have no mental imagery. There are cases of people who claim to have no mental imagery but of course they do not have mental imagery but they have thought, and they can reflect on their thought. If you ask them, well, what is it like, they have answers. But now you see the zombie is not like that at all. The zombie does not think there is anything wrong; the zombie has a rich dream life and a rich mental life and sexual fantasies, let’s suppose. The zombie loves to remember that chocolate cake he ate yesterday, and the truffles he had on an omelet the day before. All of that is within the competence of the zombie. If you do not understand the zombie that way then you are not thinking about a philosophical zombie. So if I try to imagine you as being as engaged with the world and as manifestly attentive to your perceptions and sensations as you seem to be, but not having any consciousness, then no, I do not succeed in conceiving of that. I think that is where the mistake is.

VV: But you don’t see my mental images, do you?

DD: That is right, no I do not see your mental images. But in fact you reveal your capacity to engage with mental imagery in a thousand ways. There are lots of experiments done by people like Steve Kostlan and Roger Sheppard and others that deal with imagery. And I have used some simple examples of my own. One that I use in class is the following: I say, imagine a capital letter ‘D’ as in Daniel. Now write it in 90 degrees to the left counterclockwise. Now imagine a capital letter ‘J’ as in Jerry and bring that ‘J’ up under the ‘D’, and attach it in the middle of the ‘D’ as it’s lying there. Now what do you see?

VV: An umbrella?!

DD: Of course. Now I think I have just proved that you have mental imagery.

VV: Very good, very good proof! OK, I have mental images. But what are they, what are these mental images?

DD: Well, they are not pictures in the brain. They are not even very much like pictures in the brain. But what they are like is like seeing. And the important thing to realize is that seeing is not pictures in the brain either. If we still have pictures in the brain we still have the Cartesian Theater. We do not want that. What we have to realize is that when you see, there is an image focused on your retina at the back of your eyeball. It is upside down but it is in color and it is just like a photographic image. In one sense that is the last image in the seeing process. Everything that happens after the retina is dealing with things which are less paradigmatic images. They have some properties of images. Some of the data structures that get created after the optic nerve are retina topic maps of stimulation. There is no question about that. For the one at the back of the brain we can plot stimulation and we can see how each point in your retinal image corresponds to a point of excitation on a map on that surface. In principle, you could see the pictures if you had the right sorts of dies that could exhibit them. In fact, there are some cases where this has been done. So we know that in V1 and in these other retina topic maps, of which there are now several dozen I think, the imagistic properties – the topology of an image – are still preserved. But that does not mean that the topology of the image is being utilized or being seen or being appreciated by all the processes working on them. We know when you imagine something your brain does generate activity in these retina topic areas when you imagine something visually. So there are data structures. There are patterns of stimulation in the nervous system that have structure in common with the retina topic, with the retinal image to some degree, to some extent. But the important thing is what operations are defined over this, what information can be extracted from this stimulation. This is where it becomes less and less like an image. I’m trying to think of a non-technical way of saying this now. Perhaps the easiest sort of extraction is asking questions about whether one point is between two others. Do these three points lie on a straight line or on an almost straight line? A, B and C. Can we say anything about them – is B between A and C in the picture. This is a sort of topological or geometrical property. Another question is whether this information can be extracted from your mental image and the answer is depending on how much work you’ve done to make the mental image vivid. The answer can be “Yes” or it can be “No”. To give you a graphic example of this with my students I sometimes say “I want you now please to close your eyes and imagine a purple cow. Done it?” They say “Yes”. I say “All right. Is your cow facing left of right?” And some of the people realize they can not say to even a simple question that they didn’t bother. They did something in their minds, but they did not go into enough detail even to say whether it was facing left or right. And of course, most of them, when I said “Could you see the udder?”, realized they didn’t even get that far. They imagined the cow’s head maybe and which way it was facing but they never got as far as imagining the tail or the hoofs. Once I raised the question, of course, they immediately add those details, they then do some more work, they do some more imagining. So is that an image? Well, we have to move away from everyday terms like images and senses and think about data structures and their powers. John Maynard Keynes was once asked “Do you think in words or in pictures?” And he replied, “I think in thoughts”. Now that is a very good answer. But it is also not very helpful because now the point is, well, what are thoughts? And are some of them like words, and are some of them like pictures. And the answer is, yes, some of them are a little bit like words, and some are a little bit like pictures. And they are not either words or pictures.

DV: What about colors? Obviously colors are not the same throughout the world because surfaces of the same color may differ physically. You said they are not as a pigment in the brain. So, according to your theory, what are the colors?

DD: The colors are out in the world. They are just not the patented properties you thought they were. Locke was basically right. We want to have a primary and secondary quality distinction. And recognize that secondary qualities are dispositions and things that produce ideas in us. Now, the ideas in us are not colors. The idea of green in us is no more green than the word green is green. The word stands for the color. But it is not green. Your subjective experience of green stands for the color, and it is not green either. There is a tremendous temptation to say “yes, but it does have a property which is like green.” It is a subjective green, there is the quality of green. It is not just like the word. Well, yes and no. Indeed there is not just one, but a lot of properties that your brain’s visual representation of a particular color has. That representation has many properties. Many of them are completely unnoticeable by you. They have no direct effect on your consciousness or your imagination. There are questions of where they are happening in your brain and so forth. And that does not have any direct implications. But many of the properties do have direct implications. For instance, they stimulate emotional reactions of pleasure or pain or dislike or conjure up memories. Let us make a very vivid example. Suppose you were once hurt in an automobile accident where you were struck by a car with an unusual shade of yellow. It is very likely that for the rest of your life every time you see or imagine that shade of yellow, you remember the car accident – that is simply tied tightly to your representation of that color. Now suppose that every color has links of that sort. Not as vivid, but like that. This will give each property representation a profile, an idiosyncratic profile that is actually that linkage. It’s how you identify the color. We sometimes fail to remember the fact that you can name colors. It is a bit extraordinary in a way. Especially when you consider the fact that in one of our other senses, very few of us can do it. Very few of us have a perfect pitch. If I play a random tone “…Ahhh…” you will say “What is that?” “Is it a “B” or an “F”? Who knows? Unless you have perfect pitch, you do not know. But people with perfect pitch will tell you exactly what note that is – immediately. They can just do it. Isn’t that astonishing? Well, the fact is that everybody who seems to have perfect pitch for colors. Otherwise we would have to go around with a little collection of color chips with words written on them, and somebody would hold up something and say: “What color is this?” and someone will look at the chip and say “…if this is a red, then this is going to be green”. The fact that we can identify colors says there has to be some systemic way that we organize our color vocabulary and our memories and the current experience in our imagination. There are people who suffer from color anomia. Their color vision is intact but they cannot name colors at all, except by chance. They are, in effect, like those of us that cannot name musical notes. That is not such a rare condition. There are other people who are color-blind in one half of their visual field, but they don not realize it. Of course we tend not to realize that we do not have good color perception in peripheries of our visual world. Color is something which is much more complicated. When we get into the science of it, you realize that a lot of everyday convictions are mistaken and need to be re-boxed. So I think colors are out there in the world, because colors are indeed those surfaces that reflect light in a certain ways to produce effects in us. And that is what colors are. But we can not define those properties independently of color vision, and hence of normal class of things with color vision. Let us go back before there is any vision of this planet, no multi-cellular life at all. And let us suppose there was a huge earthquake which created a giant cliff where the earth rose up. If we were to look at that cliff, we could see a lot of strata, the different colors of rock – red and yellow and grey, from the different geological eras. So there would be these visible stripes that we could follow. Now ask the question: “Were those stripes colored and visible back then?” Well, they had the same chemical composition then. And let us suppose the atmosphere was roughly the same as now. And so the iron oxides were going to be reddish colored and so forth. So in one sense, yes, sure, they were colored. But whether two stripes were the same color depends on what visual system you are talking about. Because after all, if we were are red/green color blind, there could be two stripes that to us look to be the same color and indistinguishable, but were chemically different, but not visibly different to us. We would say by definition, they are the same color to us. So we have to characterize color properties relative to a class of color vision enjoyers, or havers. Now, that does not make it relativistic. That does not mean it is not an objective property. It is plenty objective. It just means that which objective properties we are interested in depends on what is going to detect them.

VV: What if I see colors in my dreams?

DD: let us suppose you ate a horse in your dream. Did you really eat a horse? No, you just dreamed you ate a horse. There is no horse to eat. Similarly, if in your dream you saw a red, white and blue car. There was no red, white and blue car. You just dreamed you saw a white and blue car. I do not think that is going to satisfy you, but the dream does not involve really seeing a red, white and blue car. You merely dream it.

DV: That is the judgment of something?

DD: A dream is a fiction. And even if it is not in words, it is like fiction in some ways. When you read a novel, a fiction, and if the novelist says that the heroine has bright red hair, and goes on at length about bright red hair, it is a mistake for us to ask what red is. This is a fictional character and the author had to get some hair pigmented with a color that everyone really knows. And he just makes up a story about bright red hair. There are no deeper facts about how red the heroine’s hair is, whether it is really red or not. And the same is true of your dream.

VV: Very interesting. Responding to one of the previous questions, you mentioned your students. Of course, they are part of your life. My question is – do you live a philosophical life? Could you tell us a few words, what is your way of life as a philosopher?

DD: It is good question. I do not live a philosophical life as some of my colleagues do. And I certainly know people who are in fact doing philosophy every waking hour. That is not me. There are too many other things that interest me, whether I am with my family pretending to be a farmer and running my tractor, or making things in my workshop. I play with my grandchildren or go on adventures with my wife or whatever. Most of the time I am not thinking about philosophy at all. But sometimes I am. For instance, when walking down the road or staying at my house by myself, thinking while doing what I am currently doing, or driving along the highway. My wife knows that I may go silent for a long period of time driving along the highway. She knows that I am probably working out rebuttals to some argument, or working on a paper in my head. When we get talking, we find some way around it. So she is very good at not interrupting me.

VV: Let us suppose that someone wants to live according to your philosophy. It is possible? DD: Of course, it is possible because I do. I do not think there are any special maxims or principles to follow other than just to be an open-minded skeptic and to be curious. Curiosity to me is perhaps the most important thing. If I see something puzzling I want to try to get an explanation that I cannot figure out myself. I shall look for someone who can explain it to me. I do not like to leave puzzles or mysteries hanging. I want to know how and why. And if you follow that course I think you are living life like mine.

DV, VV: Thank you very much for the interview.

DD: Thank you very much for these good questions, it was fun doing this. I look forward to seeing you in person and shaking your hands in a not a distant future.

DV: Thank you very much! See you soon.

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