Daniel C. Dennett

(1942 - 2024)

If Dinesh D'Souza knew just a little bit more philosophy, he would realize how silly he appears when he accuses me of committing what he calls "the Fallacy of the Enlightenment." and challenges me to refute Kant's doctrine of the thing-in-itself. I don't need to refute this; it has been lambasted so often and so well by other philosophers that even self-styled Kantians typically find one way or another of excusing themselves from defending it. And speaking of fallacies, D'Souza contradicts himself within the space of a few paragraphs. If, as he says, Kant showed that we humans "will never know" the universe in itself, then theists couldn't "know that there is a reality greater than, and beyond, that which our senses and our minds can ever comprehend." They may take this on faith, if they wish, but they mustn't claim to know it, on pain of contradiction. We brights see no good reason to join them in their conviction, and they must admit that they see no good reason either. If they did, it wouldn't be purely a matter of faith.

I want to try to do something rather more speculative than the rest of you have done. I have been thinking recently about how one might explain some features of human reflective consciousness that seem to me to be very much in need of an explanation. I'm trying to see if these features could be understood as solutions to design problems, solutions arrived at by evolution, but also, in the individual, as a result of a process of unconscious self-design. I've been trying to think of this in the context of work in AI on the attempt to design intelligent robots – not "bed-ridden" expert systems, but systems that have to act in real time in the real world. If you want to think about something like this, you have to stray fairly far from experiments and hard empirical data; you have to get fairly speculative. Nevertheless the design efforts of people in AI do seem to bring home to conviction – if not to prove – various design constraints looming large and inescapable. If we can come to see why a system – or an organ or a behavior-pattern – must have certain features or a certain structure in order to do its task, this may help us ask the right questions, or at least keep us from dwelling on some of the wrong questions when we try to explain the machinery in the brain that is responsible for intelligent action.

How is it possible for a physical thing--a person, an animal, a robot--to extract knowledge of the world from perception and then exploit that knowledge in the guidance of successful action? That is a question with which philosophers have grappled for generations, but it could also be taken to be one of the defining questions of Artificial Intelligence. AI is, in large measure, philosophy. It is often directly concerned with instantly recognizable philosophical questions: What is mind? What is meaning? What is reasoning, and rationality? What are the necessary conditions for the recognition of objects in perception? How are decisions made and justified?

Let us begin with what all of us here agree on: folk psychology is not immune to revision. It has a certain vulnerability in principle. Any particular part of it might be overthrown and replaced by some other doctrine. Yet we disagree about how likely it is that that vulnerability in principle will turn into the actual demise of large portions--or all--of folk psychology. I am of the view that folk psychology is here for the long haul, and for some very good reasons. But I am not going to concentrate on that in my remarks. What nobody has bothered saying here yet, but is probably worth saying, is that for all of its blemishes, warts and perplexities, folk psychology is an extraordinarily powerful source of prediction. It is not just prodigiously powerful but remarkably easy for human beings to use. We are virtuoso exploiters of not so much a theory as a craft. That is, we might better call it a folk craft rather than a folk theory. The theory of folk psychology is the ideology about the craft, and there is lots of room, as anthropologists will remind us, for false ideology.

When Professor Orr published his hostile review of Darwin's Dangerous Idea in the biology journal, Evolution, last February, I was not pleased. His review was full of falsehoods and misconstruals, but I had no recourse; that journal, like most academic journals, does not permit authors to respond to reviews. Luckily for me, Orr has been so eager to warn the world of my errors that he has restated his attack, with embellishments, in the Boston Review, which has invited me to respond. Months have passed, the damage has been done, but at least I get to set the record straight.

I've been looking forward to seeing Jerry Fodor's reaction to my book, since his candidly avowed antipathy toward evolutionary arguments was one of the spurs for writing it. For instance, it was his brusque comment to me in 1985 to the effect that Searle was right about robots lacking original intentionality that set me to writing "Evolution, Error and Intentionality" (1987), and that contributed in turn to some of his recent outbursts against evolutionary approaches to these issues. Nothing clears the air quite so briskly as one of Jerry's jaunty tantrums. He is a master of blithe self-exposure, and on this occasion he is true to form.

Cognitive science, as an interdisciplinary school of thought, may have recently moved beyond the bandwagon stage onto the throne of orthodoxy, but it does not make a favorable first impression on many people. Familiar reactions on first encounters range from revulsion to condescending dismissal--very few faces in the crowd light up with the sense of "Aha! So that's how the mind works! Of course!" Cognitive science leaves something out, it seems; moreover, what it apparently leaves out is important, even precious. Boiled down to its essence, cognitive science proclaims that in one way or another our minds are computers, and this seems so mechanistic, reductionistic, intellectualistic, dry, philistine, unbiological. It leaves out emotion, or what philosophers call qualia, or value, or mattering, or... the soul. It doesn't explain what minds are so much as attempt to explain minds away.

In 1956, the mathematician John McCarthy coined the term "Artificial Intelligence" for a new discipline that was emerging from some of the more imaginative and playful explorations of the new mind-tool, the computer. A few years later he developed a radically new sort of programming language, Lisp, which became the lingua franca of AI. Unlike the sturdier, stodgier computer languages created by and for business and industry, Lisp was remarkably open-ended and freewheeling. Instead of concentrating on numbers, it was designed to take any symbols or symbol strings (lists) as its objects, and since its own machinery consisted of just such lists (and lists of lists... ), Lisp creations easily inhabited the very world they acted upon, and hence could reflect upon themselves and their own reflections indefinitely, revising and reinventing themselves, breaking down the artificial barrier between program and data. Seymour Papert was one of the most playful of the AI pioneers, and more than any of the others, his own reflections turned to the nature of that very playfulness and its role in learning and discovery. In 1980, he published Mindstorms, in which he presented his utopian vision of computers in the classroom, centering on Logo, a dialect of Lisp that he and others had developed specifically for very young children. The key design element was Turtle graphics, an inspired interface which made the children's interactions with Logo not just visible, but instantly comprehensible--feelable, you might say. The tales he told of those early encounters were compelling. They became an important ingredient in the barrage of persuasions that led teachers and schools all over America, and indeed all over the world, to invest huge sums in "computerizing the classroom." Thousands of teachers tried their hand at Logo in the classroom, with mixed results.

The time for unification in cognitive science has arrived, but who should lead the charge? The immunologist-turned-neuroscientist Gerald Edelman (1989, 1992) thinks that neuroscientists should lead--or more precisely that he should (he seems to have a low opinion of everyone else in cognitive science). Someone might think that I had made a symmetrically opposite claim in Consciousness Explained (Dennett, 1991): philosophers (or more precisely, those that agree with me!) are in the best position to see how to tie all the loose ends together. But in fact I acknowledged that unifying efforts such as mine are proto-theories, explorations that are too metaphorical and impressionistic to serve as the model for a unified theory. Perhaps Newell had me in mind when he wrote in his introduction (p.16) that a unified theory "can't be just a pastiche, in which disparate formulations are strung together with some sort of conceptual bailing wire," but in any case the shoe more or less fits, with some pinching. Such a "pastiche" theory can be a good staging ground, however, and a place to stand while considering the strengths and weaknesses of better built theories. So I agree with him.

The institution of book reviews, flawed though it may be, still performs a crucial service of resource enhancement for a discipline, funneling informed attention to at least some of the best among a superfluity of publications. During the last quarter century, Thomas Nagel's book reviews and critical essays have played a major role, shaping opinion, and thereby shaping the field. Now he has gathered his favorites in a collection, ten in philosophy of mind, and a dozen in ethics and political philosophy, supplemented by the view from today: brief reactions to the individual pieces, and a fascinating introduction, part intellectual autobiography and part reflection on the state of the discipline. The other minds of the title are those of Freud (and Richard Wollheim and Adolf Grünbaum), Wittgenstein (and David Pears), Noam Chomsky, Jerry Fodor, David Armstrong, myself, Brian O'Shaughnessy and John Searle in the philosophy of mind, and Aristotle (and John Cooper), John Rawls, Robert Nozick, Richard Hare, Bernard Williams, Thomas Schelling, Ronald Dworkin, Alasdair MacIntyre, and Leszek Kolakowski in ethics and political philosophy. Do not be misled by the dust jacket. The picture of brains is as inappropriate as it is ugly; Nagel's interest in the mind has always been more driven by his interest in the mind's role in ethics, than by a fascination with neuroscience. He is a "moral psychologist," not a "cognitive scientist."

In other words, it's a perfect season for naysayers, and philosophers have risen to the occasion. The most radical is Colin McGinn, former Wilde Reader of Mental Philosophy at Oxford, who has recently taken a position at Rutgers University in New Jersey. The Problem of Consciousness is a collection of eight essays, two of which have not previously been published. McGinn's central thesis is that the problem of consciousness is systematically insoluble by us (Martians or demigods might have better luck). Our brains just weren't meant to get a grip on this tough problem, but--there, there, it's all right--we mustn't draw the conclusion from the fact that we can't understand it, that the mind is intrinsically mysterious. After all, whoever promised that we should be able to understand all possible good science?

There was language long before there was writing, a fact that we literate investigators tend to underestimate. Today we are building the information superhighway, and for several millennia the written word has been the primary medium of cultural transmission, but for at least a thousand millennia before that, the main medium of information transfer from generation to generation--standing alongside the genome itself and the information embodied directly in artifacts--was the well-beaten path of word of mouth. Language was already a highly refined biological product, complete with all its modern appurtenances, long before writing was invented.

In 1979, Douglas Hofstadter published Gödel Escher Bach: An Eternal Golden Braid, a brilliant exploration of some of the most difficult and fascinating ideas at the heart of cognitive science: recursion, computation, reduction, holism, meaning, "jootsing" (jumping out of the system), "strange loops", and much, much more. What made the book's expositions so effective were a family of elaborate (and lovingly elaborated) analogies: the mind is like an anthill, a formal system is like a game, theorem and nontheorem are like figure and ground, Bach's Inventions are like dialogues, and much, much more. The whole analogy-package was wrapped in layers of self-conscious reflection. "Anything you can do I can do meta-" was one of Doug's mottos, and of course he applied it, recursively, to everything he did.

When one says that cultures evolve, this can be taken as a truism, or as asserting one or another controversial, speculative, unconfirmed theory. Consider a cultural inventory at time t: it includes all the languages, practices, ceremonies, edifices, methods, tools, myths, music, art, and so forth, that compose a culture. Over time, the inventory changes. Some items disappear, some multiply, some merge, some change. (When I say some change, I mean to be neutral at this point about whether this amounts to their being replaced by similar items, or their undergoing a transformation.) A verbatim record of this history would not be science; it would be a data base. That is the truism: cultures evolve over time. Now the question remains: how are we to explain the patterns found in that data base? Are there any good theories or models of cultural evolution?

Back and forth swings the pendulum. It is remarkable that Baars can claim that “many scientists now feel that radical behaviorists tossed out the baby with the bathwater” while not being able to see that his own efforts threaten to be an instance of the complementary overshooting–what we might call covering a nice clean baby with dualistic dirt. Yes indeed, radical behaviorism of Skinner’s variety fell from grace some years ago, with the so-called cognitive revolution, to be replaced by a sort of cognitivistic behaviorism that has plenty of room for inner processes, for talking to yourself, for mental imagery, for hunches, feelings, pains, dreams, beliefs and hopes and expectations, but only so long as these are understood to be physical (“informational” or “computational”) processes that could be accomplished by the machinery of the brain. It is an interesting speculative question whether William James would have been a wholehearted cognitivist, or whether he would have insisted that what he meant by the stream of consciousness had to be sharply distinguished from the streams of mere information-manipulation discernible in the activities of cortical subsystems, etc., etc. Making a home for consciousness in the brain, for a distinction between unconscious information-transformations and conscious ones, for instance, is now the work of many hands in many fields (See, e.g., Dennett, 2001, and the other essays in the special issue of Cognition devoted to the cognitive neuroscience of consciousness). The main methodological principle of this research is one shared with the radical behaviorists: only intersubjectively accessible data are to be admitted in this natural science of consciousness. If that allegiance, by itself, counts as ‘behaviorism,” then we should all be behaviorists, and indeed the very researchers Baars cites (Singer, Ericsson and Simon, Hilgard, Crick, and Edelman) scrupulously and unapologetically are behaviorists in this minimal sense. They interview their subjects, under controlled conditions, and take their reports seriously–but not as infallible guides to their subjects’ subjectivity..

Clark and Karmiloff-Smith (CKS) have written an extraordinarily valuable paper, which sympathetically addresses what has all too often been an acrimonious and ideology-ridden "debate" and begins to transform it into a multi-perspective research program. By articulating the submerged hunches on both sides in a single framework, and adding some powerful new ideas of their own, they dispel much of the smoke of battle. What we can now see much more clearly is the need for a model of a brain/mind that, as they say, "enriches itself from within by re-representing the knowledge that it has already represented."

On the back of the dust jacket of this fine book, one can barely make out two representations of a customized penny for our thoughts, drawn by John Haugeland. Accompanying Honest Abe on the heads side appear the words AExistential Commitment,@ AThought,@ and ASelf;@ while tails shows the Lincoln Memorial and E pluribus unum, surrounded by two unlikely additions: AConstituted Domain, @ and AObjects@. Haugeland explains: AThe basic Kantian/Heideggerian conclusion can be summed up this way: the constituted objective world and the free constituting subject are intelligible only as two sides of one coin. @ Not everything with eyes and ears and a brain is a Afree constituting subject @; apes and dogs and dolphins don =t have ontologies because they don =t have thoughts; they don =t have thoughts because they don =t have the Acensoriousness@ in their cultures or social structures that provides the leverage for Understanding, distinguishing a true thought from a false thought, and without that, thoughts cannot really have content. There are, to be sure, important differences in the Umwelt or manifest image of different species, but cats have no more metaphysics than clams or chrysanthemums do. Objects are constituted by people only, and our ultimately moral sense of norms, of AExistential@ commitment, far from being a sort of ethical add-on to the factual world of objects and properties, is the very ground on which our capacity to know, and reflect upon, objects depends.

PRESIDENT BUSH, announcing this month that he was in favor of teaching about "intelligent design" in the schools, said, "I think that part of education is to expose people to different schools of thought." A couple of weeks later, Senator Bill Frist of Tennessee, the Republican leader, made the same point. Teaching both intelligent design and evolution "doesn't force any particular theory on anyone," Mr. Frist said. "I think in a pluralistic society that is the fairest way to go about education and training people for the future.&quot.

Consider this chess puzzle. White to checkmate in two. It appeared recently in the Boston Globe, and what startled me about it was that I had thought it had been proven that you can’t checkmate with a lone knight (and a king, of course). This is a counterexample, a strange circumstance that can arise in a legal game of chess. This fact is a higher-order truth of chess, namely that the “proof” that you can never checkmate with a lone knight and king is unsound. Now let’s consider chmess (I made up the term); it’s the game that you get by allowing the king to move two spaces, not one, in any direction. I made it up and I don’t know if anybody has ever played it. I have no idea whether it’s worth playing. Probably it isn’t, but it doesn’t matter; it’s not even worth our attention long enough to figure out. But a moment’s reflection reveals that there are exactly as many higher-order a priori truths of chmess as there are of chess, namely, an infinity of them. And no doubt they would be roughly as difficult to discover and to prove as the higherorder truths of chess. There are people who make a living working out the truths of chess and certainly it’s been a big avocation for many other people. But I doubt if anybody yet has spent more than 5 minutes trying to work out the a priori truths, and the higher-order truths, of chmess.

After decades of persistent work by researchers in many fields, building foundations and patiently filling in details, the gigantic jigsaw puzzle of consciousness is beginning to come into focus. As large assemblies fall into place with a gratifying convergence of details drawn from different disciplines, the pace is quickening. Everybody wants to be in on the delicious task of describing what the Big Picture is going to look like, predicting the outlines before the mopping up operations confirm them. Well, not quite everybody. There are also those who dislike what they see happening: consciousness is turning out to be "just" a great big jigsaw puzzle. What? No cosmic revolutions in quantum (or meta-) physics? No Impenetrable Mysteries? Bummer!

In my opinion, the two main topics in the philosophy of mind are content and consciousness, and they have received about equal attention from me. As the title of my first book, Content and Consciousness suggested, that is the order in which they must be addressed: first, a theory of content or intentionality--a phenomenon more fundamental than consciousness--and then, building on that foundation, a theory of consciousness. Over the years I have found myself recapitulating this basic structure twice, partly in order to respond to various philosophical objections, but more importantly, because my research on foundational issues in cognitive science led me into different aspects of the problems. The articles in the first half of Brainstorms composed in effect a more detailed theory of content, and the articles in the second half were concerned with specific problems of consciousness. The second recapitulation devoted a separate volume to each half: The Intentional Stance is all and only about content; Consciousness Explained presupposes the theory of content in that volume and builds an expanded theory of consciousness. My more recent books, Darwin's Dangerous Idea and Kinds of Minds, extend the scope of my earlier work, bringing out the evolutionary foundations of both the theory of intentional systems and the theory of consciousness. A summary of both of these in their current versions follows a review of how I got there.