Daniel Dennett — philosopher of mind, critic of religion, public defender (and, more importantly, dedicated deployer) of Darwinism, developer and distributor of “dangerous” ideas — D. Dennett: double-D, double-E, double-N, double-T (not quite in that order) has even played his own double in print and on the screen: in a mind-bending parable called “Where Am I?” (1978) and in an odd film partly based on this parable called Victim of the Brain (1988):
Would I submit to a surgical procedure that would completely remove my brain, which would then be placed in a life-support system at the Manned Spacecraft Center in Houston? Each input and output pathway, as it was severed, would be restored by a pair of microminiaturized radio transceivers, one attached precisely to the brain, the other to the nerve stumps in the empty cranium. No information would be lost, all the connectivity would be preserved. At first I was a bit reluctant.
And this “doubling” of Dennett is not the least of it! “Yes, we have a soul,” Dennett proclaims, “but it’s made of lots of tiny robots.” Although he is clearly a connoisseur of colorful metaphors, philosophical puzzles, and fantastic thought experiments (often in the style of his occasional co-author and fellow Stanford Presidential Lecturer Douglas Hofstadter), Dennett is one of our most serious and influential philosophers of mind. His work is widely cited among academic philosophers and cognitive scientists, but at the same time he conscientiously makes that work accessible to general readers.
Dennett is University Professor and Austin B. Fletcher Professor of Philosophy at Tufts University, and co-director of the Center for Cognitive Studies. Many of his book titles reflect these identities, philosopher and cognitive scientist — The Intentional Stance (1987), Content and Consciousness (1969), The Mind’s I (1981, with Hofstadter), and Consciousness Explained (1991) all clearly match these aspects of his work. But some of Dennett’s most influential recent works have fit not so obviously into these categories: Darwin’s Dangerous Idea (1995), which was a finalist for both the National Book Award and the Pulitzer Prize, and Breaking the Spell: Religion as a Natural Phenomenon (2006), perhaps the most engaging, substantive, and subtle — and the least pulpit-pounding — of the recent crop of best-selling books about atheism.
Dennett’s wide-ranging books really all center on one thing: the human mind, whether it goes by the name of “consciousness,” “cognition,” or even “soul.” Even the “lots of tiny robots” in Dennett’s materialist definition of the soul (quoted above) may sound like the same sort of jocular science fiction as the disembodied brain in “Where Am I?” — but in fact the idea refers explicitly to his very serious “Multiple Drafts Model” of consciousness, in which there is no single point of cognition, no single line of demarcation between the unconscious and the conscious, and no single “self” even to “be” conscious. Although it wasn’t developed in a vacuum, and although it has remained far from uncontroversial since he elaborated it in 1991, this stunning model of what goes on in the human cranium remains one of Dennett’s profoundest contributions to the contemporary philosophy of mind.
Whether he approaches the mind through philosophy (strictly understood, as an academic discipline), cognitive science (a field to which he is an avid contributor), or biology (specifically Darwinian evolution, which has clearly become the guiding tool in Dennett’s work of the past two decades), Dennett has always been less interested in abstract concepts about the universe or any universal truths the universe may embody than in the mechanics and origins of the human mind itself. Even his most recent foray into the study of religion — a field not necessarily outside his home base of philosophy (although Dennett’s approach is as far as possible from a traditional theological one) — is really a study of religion as it exists in human mind(s), of religion as an artifact of human evolution, of Religion as a Natural Phenomenon, as the book’s subtitle frames it.
So while it is something of an oversimplification of his remarkable work, it is not at all incorrect to summarize Dennett’s principal topic as philosophy of mind. He himself, in numerous contexts and from the very beginning of his career, has divided this topic into two main sub-topics: content and consciousness. Not only is this the very title of his first book; he also begins an illuminating 1994 essay, Self-Portrait, with the assertion that not only have these two sub-topics defined his career, but they have done so in precisely the same order (with some recapitulation over the years) in which he presents them, 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 (Brainchildren, p. 354).
Dennett calls his particular ordering of content and consciousness a renegade one among philosophers, who traditionally consider consciousness as the fundamental phenomenon on which content depends. (Put another way, philosophers unquestioningly follow Decartes’ order, cogito — “I am conscious” — ergo sum — “therefore I have content,” rather than Dennett’s opposite ordering.) Some may see this difference as superficial or inconsequential. But Dennett (and, in his telling, the entire field of academic philosophy) clearly does not; rather, as he writes in his Self-Portrait, this difference of perspective is fundamental, infecting the intuitions with which all theorizing must begin, and it is thus the source of some of the deepest and most persistent disagreements in the field (Brainchildren, p. 354). After his first book set out this renegade view, his next two major monographs reinforced its centrality, with The Intentional Stance devoted to content, and Consciousness Explained, obviously, to consciousness.
As Dennett’s very thorough explorations of these two major topics in the philosophy of mind evolved from academically-oriented works published by scholarly presses, and then into works for a broader (but still very serious) audience published by trade presses, so have his philosophical topics broadened. His two most recent major monographs (in a bibliography studded not only with several hundred essays, but also with several collections thereof) may, as noted above, seem like departures from the philosophy of mind world: the first, Darwin’s Dangerous Idea, was (ostensibly) about biology, and the second, Breaking the Spell, (also ostensibly) about theology.
But of course, as hinted at above, Dennett gives no cause for one to accuse him of either dilettantism or gross multiplicity of purpose. Although each of these books is a remarkably engaging, deep and thoughtful account of its principal topic, Dennett writes them without the pretense of any expertise other than his own, and without stepping on the toes of the specialists. Of Darwin’s Dangerous Idea he writes, This book is largely about science but is not itself a work of science (p. 11); and of Breaking the Spell he writes, I am a philosopher, not a biologist or an anthropologist or a sociologist or historian or theologian. We philosophers are better at asking questions than at answering them, and this may strike some people as a comical admission of futility (p. 19). These are not admissions of (false) modesty, and neither are they attempts to deflect criticism by claiming amateur status. They are, rather, up-front epistemological and methodological statements, and as such, bold defenses of Dennett’s qualifications to write outside his field.
This boldness and openness are characteristic of Dennett’s style of composition and argumentation, which is a no-nonsense affair. That is not at all to say that he’s humorless or fun-free! On the contrary, in addition to his earlier forays into philosophical science fiction and film, his mature writings (somewhat more serious) are still spiced with Quinian crossword puzzles (simple crosswords with two equally good solutions, named after Dennett’s Harvard teacher, the philosopher W. V. O. Quine), drolly named tools like intuition pumps (a sort of thought experiment designed to elicit intuitive, if sometimes tellingly incorrect, responses — see note  below), and wonderful coinages frequently based on the name of some other philosopher. (There’s an entry — which Dennett apparently didn’t write — in The Philosophical Lexicon — which he did edit — that reads as follows: dennett, v. (1) To while away the hours defining surnames; hence, dennettation, n. (2) The meaning of a surname.)
Dennett’s rich coinages and metaphors, whether they’re based on personal references or subtle demarcations among philosophical ideas, are always both very precise and remarkably memorable. Take, for example, his term “greedy reductionism.” On the one hand, he surely understands that he’s going against the flow of common usage by claiming a positive connotation for the philosophically neutral term “reductionism”; on the other hand, he also understands precisely why “reductionism” might be understood negatively by non-philosophers, so he attaches the clearly negative attribute “greedy” to that kind of “reductionism.” How does he do this? He begins with two of his central metaphors for the (also metaphorical) building of an explanation for some natural phenomenon, the crane and the skyhook:
Cranes can do the lifting work our imaginary skyhooks might do, and they do it in an honest, non-question-begging fashion. They are expensive, however. They have to be designed and built, from everyday parts already on hand, and they have to be located on a firm base of existing ground. Skyhooks are miraculous lifters, unsupported and insupportable. Cranes are no less excellent as lifters, and they have the decided advantage of being real.
(Darwin’s Dangerous Idea, p. 75)
With these two potential tools in his explanatory kit, Dennett uses the obviously negative metaphor to illustrate the negative sense of the term, and the obviously positive one for the positive sense: We must distinguish reductionism, which is in general a good thing, from greedy reductionism, which is not. The difference, in the context of Darwin’s theory, is simple: greedy reductionists think that everything can be explained without cranes; good reductionists think that everything can be explained without skyhooks (Darwin’s Dangerous Idea, p. 81-82). So what it means to call Dennett’s style of argumentation no-nonsense is that he takes the utmost care to bring his readers along with him as he embarks on his complex journeys of discovery. Continuing with the architectural metaphor: Dennett’s works are complex structures in which he anticipates the possible objections of interlocutors both real and imaginary, methodically builds his arguments from their foundational questions, carefully places the load-bearing beams of experiment, and then sculpts his conclusions all the way up to the pinnacles of their most unexpected implications.
But let us examine another of Dennett’s own explanatory metaphors for his own work (is this a “meta-metaphor”?): Of his central thesis in Consciousness Explained he writes: This is still not an easy idea to understand, let alone accept. We must build several more roads to it (p. 170). This conscious, conscientious, and device-baring technique — building multiple roads toward a difficult idea — manifests itself in explicitly reader-friendly compositions. Breaking the Spell, Darwin’s Dangerous Idea, and Freedom Evolves, for example, all have this curious structural trait: each chapter break is bridged by a one-paragraph summary of the chapter just finished, and another of the chapter to come, leading the reader carefully through what is bound to be a complex argument. Even so, some very technical matters are perhaps best left out of a book for the general reader.... Or rather, not left out: that would be so non-Dennettian! Rather, they are carefully noted and then moved to the back of the book:
The questions are important — indeed, crucial to my whole project — since they put into doubt the very possibility of conducting the inquiry I am embarking on, but they can be postponed until after the theory sketch is completed. If you disagree, then before continuing with chapter 4 you should turn directly to appendix B, Some More Questions About Science, which deals with these questions, spelling out in more detail, and defending, the path by which we can work together to find mutual agreement about how to proceed and what matters.
(Breaking the Spell, p. 93)
Consciousness Explained likewise comes equipped with two appendices, A (for Philosophers) and B (for Scientists). These back-of-the-book sections are not where you’d look, as in a high-school textbook, for the answers: they contain, rather, even deeper questions and discussion; they fill in some gaps; they suggest experiments that might prove (or disprove!) Dennett’s controversial hypotheses. Remarkably for the characteristically bold Dennett, those supplemental questions that he suggests, and those problematic aspects of his thesis that he offers for experimental falsification, those aspects of his theories that he freely acknowledges as still unresolved, are the very embodiment of intellectual integrity and modesty, his often audacious book titles notwithstanding.
The title of Dennett’s 2009 Stanford Presidential Lecture, The Evolution of ‘Why’ as the Key to Free Will, harks back to Darwin’s Dangerous Idea: the dangerous idea is Darwin’s revolutionary alternative way to understand the teleological question — the why question — in algorithmic, mechanistic, materialistic ways. Dennett’s contribution to the discussion of the biggest questions of the human condition (such as that of “free will” in this lecture) is his insistence on careful, sober — though not somber — reasoning: explaining these marvelous and difficult phenomena without miraculous skyhooks, and revealing at the same time that cranes, though not at all miraculous, are all the more remarkable for the explanatory work they do.
 Where Am I?, published in Dennett, Brainstorms, and in Douglas Hofstadter and Daniel Dennett, The Mind’s I, from which this quote is taken, p. 218. The film Victim of the Brain, directed by Piet Hoenderdos in 1988, is available in a low-resolution version on Google Video.
 Freedom Evolves, p. 1, and Breaking the Spell, p. 302. As Dennett explains in a note to this latter appearance, “This was the headline, in Italian, of an interview with me by Giulio
Giorelli published in Corriere della Sera in Milan in 1997. Ever since then, I
have adopted it as my slogan, opening my book Freedom Evolves with it” (Breaking the Spell, p. 408n).
 Intuition pumps are powerful pedagogical devices. Descartes’ ‘cogito ergo sum’ thought experiment is generally agreed to be logically suspect, if not downright defective. It has inspired literally dozens of reinterpretations and defenses; many philosophy professors would dismiss all these commentaries while never dreaming of removing Descartes’ dramatic idea from the syllabus. Even great intuition pumps can mislead as much as they instruct (Elbow Room, p. 18).
 It is worth mentioning in this context Dennett’s vigorous debate in the New York Review of Books about Darwinian evolution with another fellow Stanford Presidential Lecturer, the late Stephen Jay Gould. Dennett, while acknowledging his outsider status as the non-biologist in this debate, has always “done his homework,” and much more.
 Andrew Brook and Don Ross quipped about Dennett’s title Consciousness Explained that modesty is a virtue to be kept for special occasions. Daniel Dennett, Cambridge University Press, (2002), p. 8.