From Bacteria to Bach and Back: The Evolution of Minds

by Daniel C. Dennett

1.Darwin’s strange inversion of reasoning 2.Reasons without reasoners 3.Competence without comprehension 4.Turing’s strange inversion of reasoning 5.Information as design worth stealing 6.Darwinism about Darwinism 7.Feral neurons 8.Words striving to reproduce 9.The evolution of the evolution of culture 10.Hume’s strange inversion of reasoning 11.Consciousness as a user-illusion 12.The age of post-intelligent design

Throughout this book I will exploit the perspective of reverse engineering, taking on the premise that every living thing is a product of nonmysterious physical processes that gradually brought all the elements together, refining them along the way, and eventually arrived at the working system we observe, or at some hypothesized intermediate system, a stepping-stone that would represent clear progress toward the living things we know exist.

In a highly influential essay, Stephen Jay Gould and Richard Lewontin (1979) coined the phrase “Panglossian paradigm” as a deliberately abusive term for the brand of biology—adaptationism—that relies on the methodological principle of assuming, until proven otherwise, that all the parts of an organism are good for something. That is, they have useful roles to play, such as pumping blood, improving speed of locomotion, fending off infection, digesting food, dissipating heat, attracting mates, and so forth. The assumption is built right into the reverse-engineering perspective that sees all living things as efficiently composed of parts with functions.

Science, we are often told, has banished the telos, and we have Darwin to thank for this.

So seductive is the lure of Cartesian thinking that in order to resist it, some think we should follow the abstemious principle that whenever there is any risk of infection by prescientific concepts—of souls and spirits, Aristotelian teleology and the like—it is best to err on the side of squeaky-clean, absolute quarantine.

One of the further forces in operation here is the desire not to give aid and comfort to creationists and the Intelligent Design crowd. By speaking of purpose and design in Nature, we (apparently) give them half their case; it is better, some think, to maintain a stern embargo on such themes and insist that strictly speaking nothing in the biosphere is designed unless it is designed by human artificers. Nature’s way of generating complex systems (organs, behaviors, etc.) is so unlike an artificer’s way that we should not use the same language to describe them.

I disagree with this overkill austerity, which can backfire badly.

Which battle do we want to fight? Do we want to try to convince lay people that they don’t really see the design that is stunningly obvious at every scale in biology, or would we rather try to persuade them that what Darwin has shown is that there can be design—real design, as real as it gets—without an Intelligent Designer? We have persuaded the world that atoms are not atomic, and that the Earth goes around the Sun. Why shrink from the pedagogical task of showing that there can be design without a designer? So I am defending here (once again, with new emphasis) the following claim: The biosphere is utterly saturated with design, with purpose, with reasons. What I call the “design stance” predicts and explains features throughout the living world using the same assumptions that work so well when reverse-engineering artifacts made by (somewhat) intelligent human designers.

Perhaps the best way of seeing the reality, indeed the ubiquity in Nature, of reasons is to reflect on the different meanings of “why.” The English word is equivocal, and the main ambiguity is marked by a familiar pair of substitute phrases: what for? and how come?” “Why are you handing me your camera?” asks what are you doing this for? “Why does ice float?” asks how come: what it is about the way ice forms that makes it lower density than liquid water? The how come question asks for a process narrative that explains the phenomenon without saying it is for anything. “Why is the sky blue?” “Why is the sand on the beach sorted by size?” “Why did the ground just shake?” “Why does hail accompany thunderstorms?” “Why is this dry mud cracked in such a fashion?”

Compare four questions: 1.Do you know the reason why planets are spherical? 2.Do you know the reason why ball bearings are spherical? 3.Do you know the reason why asteroids aren’t spherical? 4.Do you know the reason why dice aren’t spherical? The word “reason” is acceptable in all four questions (at least to my ear—how about yours?), but the answers to (1) and (3) don’t give reasons (there aren’t any reasons); they give causes, or process narratives. In some contexts the word “reason” can mean cause, unfortunately. You can answer questions (2) and (4) with process narratives along the lines of “well, the ball bearings were made on a lathe of sorts, which spun the metal … and the dice were cast in boxlike molds …” but those are not reasons.

The prebiotic or abiotic world was not utter chaos, a random confetti of atoms in motion. In particular there were cycles, at many spatio-temporal scales: seasons, night and day, tides, the water cycle, and thousands of chemical cycles discoverable at the atomic and molecular level. Think of cycles as “do-loops” in algorithms, actions that return to a starting point after “accomplishing” something—accumulating something, or moving something, or sorting something, for instance—and then repeating (and repeating and repeating), gradually changing the conditions in the world and thus raising the probability that something new will happen. A

this process where persistence turns gradually into multiplication, and we see a proliferation of some type of items where before there were none and we ask, “Why are we seeing these improbable things here?” The question is equivocal! For now there is both a process narrative answer, how come, and a justification, what for. We are confronting a situation in which some chemical structures are present while chemically possible alternatives are absent, and what we are looking at are things that are better at persisting in the local circumstances than their contemporary alternatives.

We are witnessing an “automatic” (algorithmic) paring away of the nonfunctional, crowded out by the functional. And by the time we get to a reproducing bacterium, there is functional virtuosity galore. In other words, there are reasons why the parts are shaped and ordered as they are. We can reverse engineer any reproducing entity, determining its good and its bad, and saying why it is good or bad. This is the birth of reasons,

So there were reasons long before there were reason-representers—us. The reasons tracked by evolution I have called “free-floating rationales,” a term that has apparently jangled the nerves of some few thinkers, who suspect I am conjuring up ghosts of some sort. Not at all. Free-floating rationales are no more ghostly or problematic than numbers or centers of gravity. Cubes had eight corners before people invented ways of articulating arithmetic, and asteroids had centers of gravity before there were physicists to dream up the idea and calculate with it. Reasons existed long before there were reasoners. Some find this way of thinking unnerving and probably “unsound,” but I am not relenting. Instead I am hoping here to calm their fears and convince them that we should all be happy to speak of the reasons uncovered by evolution before they were ever expressed or represented by human investigators or any other minds.

“Ontology” comes from the Greek word for thing. In philosophy, it refers to the set of “things” a person believes to exist, or the set of things defined by, or assumed by, some theory.

It has proved more than convenient to extend the term “ontology” beyond this primary meaning and use it for the set of “things” that an animal can recognize and behave appropriately with regard to (whether or not animals can properly be said to have beliefs) and—more recently—the set of “things” a computer program has to be able to deal with to do its job (whether or not it can properly be said to have beliefs).

This common ontology was usefully named the manifest image by Wilfrid Sellars (1962).

That’s the sense in which the “image” is “manifest”: it is obvious to all, and everybody knows that it is obvious to all, and everybody knows that, too. It comes along with your native language; it’s the world according to us.

Sellars contrasted this with the scientific image, which is populated with molecules, atoms, electrons, gravity, quarks, and who knows what else (dark energy, strings? branes?). Even scientists conduct most of their waking lives conceiving of what is going on in terms of the manifest image.

Unlike the term “ontology,” “manifest image” and “scientific image” have not yet migrated from philosophy to other fields, but I’m doing my best to export them, since they have long seemed to me to be the best way I know to clarify the relationship between “our” world and the world of science.

The idea that every organism has its ontology (in the elevator sense) was prefigured in Jakob von Uexküll’s (1934) concept of the organism’s Umwelt, the behavioral environment that consists of all the things that matter to its well-being. A close kin to this idea is the psychologist J. J. Gibson’s (1979) concept of affordances: “What the environment offers the animal for good or ill.” Affordances are the relevant opportunities in the environment of any organism: things to eat or mate with, openings to walk through or look out of, holes to hide in, things to stand on, and so forth.

Remember, biology is reverse engineering, and reverse engineering is methodologically committed to optimality considerations. “What is—or was—this feature good for?” is always on the tip of the tongue; without it, reverse engineering dissolves into bafflement.

To distance these phenomena from our contemporary preoccupation with systems of information encoding, I will call them instances of semantic information, since we identify the information of interest to us on a particular occasion by specifying what it is about (events, conditions, objects, people, spies, products …).

These are different items of semantic information (don’t say “bits of information,” because “bits,” while perfectly good units, belong to the other, Shannon, sense of the term).

“Information is information, not matter or energy. No materialism that does not admit this can survive at the present day.”

Words, one might say, are a kind of virtual DNA, a largely digitized medium that exists only in the manifest image.

Some philosophers will frown at this point, and worry that I am gliding over some treacherous thin ice. Do words even exist? Are they part of your ontology? Should they be? This talk of words being “made of information” is pretty dicey, isn’t it? Just a lot of hand-waving? Some philosophers will bite the bullet at this point and insist that words don’t exist, strictly speaking. They have no mass, no energy, no chemical composition; they are not part of the scientific image, which they say should be considered the ultimate arbiter of ontology. But words are very prominent denizens of our manifest image, and even if science doesn’t have to refer to them or mention them, you couldn’t do science without using them, so they should perhaps be included in our ontology. They loom large for us, readily occupying our attention.57

Claims about nonexistence are almost always slippery, especially when scientists wax philosophical or philosophers wax scientific. We can all agree—can’t we?—that mermaids and poltergeists and phlogiston and élan vital don’t exist, but controversies simmer in some quarters over genes, strings (of string theory), public languages (as contrasted with idiolects), numbers, colors, free will, qualia, and even dreams. Sometimes, the negative claims are based on a highly austere doctrine of reality according to which nothing really exists except “atoms and the void” (or subatomic particles and physical fields, or just one subatomic particle dashing back and forth between the beginning of time and the end of time, weaving a fabric with itself—a proposal by the physicist John Archibald Wheeler).

According to my theories, consciousness is not a nonphysical phenomenon and free will is not a phenomenon isolated from causation, and by the lights of Wright and Strawson (and others), I ought to have the courage then to admit that neither consciousness nor free will really exists. (Perhaps I could soften the blow by being a “fictionalist,” insisting that they don’t really exist but it is remarkably useful to act as if they did.) I don’t see why my critics think their understanding about what really exists is superior to mine, so I demur.

At last we are ready to put the pieces together and examine human consciousness as a system of virtual machines