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October 09, 2004

Dennett, evolution, and "higher purpose"

Did Daniel Dennett admit that there is a "higher purpose" to life? asks Robin Varghese of 3quarksdaily. This strikes me as an odd way of putting the question. The alleged "admission" is to be found in an interview between Robert Wright and Daniel Dennett.

You can watch the Wright/Dennett Interview in its entirety. Then decide whether Wright's synposis is fair:

I have some bad news for Dennett's many atheist devotees. He recently declared that life on earth shows signs of having a higher purpose. Worse still, he did it on videotape, during an interview for my website (You can watch the relevant clip here, though I recommend reading a bit further first so you'll have enough background to follow the logic.) [Editor's Note: Since this article was published, Dennett has claimed that it misrepresents his views. Robert Wright responds to Dennett here.]

I submit Wright is being incredibly disingenuous in his synopsis of the interview and, I might add, in his Editorial Note. The video doesn't misrepresent Dennett's views. Dennett didn't object to the interview, he objected to Wright's post hoc editorializing. Dennett wrote:

"This is ridiculous: Wright misinterprets his own videoclip (I am grateful that it is available uncut on his website, so that everybody can see for themselves).

[Via Daily Dish. Yes, you read right.]

Dennett's View

Dennett believes that natural selection explains the purposes we see in living things. By "purpose" Dennett means something closer to Aristotelian teleology than theology. Dennett believes that eyes are quite literally for seeing, that wings are for flying, that gills are for breathing, and so on. In the pre-Darwinian era, these commonplace observations were treated as an open-and-shut case for intelligent design. Living things do seem different from, say, geological formations. A cave system can be incredibly complex, but it doesn't seem like the various bits and pieces are for anything. It's easy to imagine how this intricate object could simply reflect a bunch of stuff that happened.

Dennett argues that Darwin made atheism intellectually respectable because the theory of natural selection explains how a non-conscious process could generate complex, designed organisms.

Wright's Hypothetical

Wright is making a rather strange argument: If the evolution of life on earth were like the embryological development of individuals, wouldn't that be evidence of Intelligent Design? Wright's key points seem to be i) evolution is directional; ii) embryological development is directional. He claims that in both cases we see developing complexity and integration of function. Wright asserts that life on earth can be seen as a directional process of organism development in which human beings assume the function of the planetary nervous system:

Meanwhile, as the human species is becoming a global brain, gradually assuming conscious control of the planet's stewardship, other species—also descended from that single primitive cell that lived billions of years ago—perform other planetary functions. Trees are lungs, for example, generating oxygen.

Dennett offers a qualified assent to (i). He agrees that there has been a trend, though by no means an inevitable or irreversible trend, towards evolutionary complexity. Dennett has several reservations about (ii). As you can see in the video, he objects that embryological development doesn't necessarily progress towards ever-greater complexity.

Wright seems to arguing from unarticulated premises, which I will attempt to spell out. We agree natural selection designs organisms by differential reproduction of self-regulators. Natural selection helps explain the transition from single cell to complex organism, both at the level of the type and the level of the individual.

Suppose that the Earth is one big organism. Wright implies that natural selection couldn't explain Organism Earth--which seems right because the earth itself doesn't have the properties necessary to participate in natural selection. It's not a self-replicator, it doesn't have heritable components that contribute differentially to the survival of its offspring, etc. So, maybe we need ID to explain Organism Earth, even if blind natural selection explains the design inherent in individual earth species.

As I think Dennett argues in the video, this argument assumes that Organism Earth shows evidence of purpose in the same sense as wings and eyes. This is a dubious assertion. There's no particular reason to believe that the earth is relevantly analogous to an organism. The features of earth aren't obviously "for" things in the same sense as bodily structures. Moreover, there's no reason to think that the earth was more "suited to" or "designed for" life on earth as we know it, as opposed to other possibilities: no life at all, a "saw tooth" pattern of rising and falling average complexity, etc. Wright seems to be implying that earth must have been created with the purpose of fostering life, but he doesn't supply any motivation for his view.

When pressed, Dennett agrees that if the history of life on earth were relevantly like embryological development, then that might constitute evidence of ID. Note that by "evidence" Dennett doesn't mean proof or presumptive proof. Wright asks whether, if such similarities could be substantiated empirically, whether this might count in favor of some version of ID. He's not asking whether this would be a knock down argument for ID, or even whether ID would be the best explanation for these similarities. Wright is simply asking whether an ID-proponent could find these discoveries encouraging (were anyone to make them.) Big deal.

I just lost a lot of respect for Robert Wright. He took an interesting exchange of ideas, published a grandstanding gloss, and issued a graceless response when challenged.

[In the interest of full disclosure I should add that Dennett is my mentor, friend, and former professor.]

[Edit: Tim Sandefur has an excellent analysis of the Dennett/Wright flap. Hat tip to Ed Brayton of Dispatches from the Culture Wars. Also, here's another good post from Dan of Doing Things With Words.]


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» Dennett's Response, via Andrew Sullivan from Dispatches from the Culture Wars
Yesterday, I wrote about Robert Wright's claim that Daniel Dennett had reluctantly admitted that there is evidence of design in nature. Today, Andrew Sullivan has Dennett's reply: "This is ridiculous: Wright misinterprets his own videoclip (I am gratef... [Read More]


Good points. Yes, the title of the post is not the best way of describing the events.

Of course, Wright is being self-serving in the interview. But I think that these statements--"Dennett believes that natural selection explains the purposes we see in living things. By 'purpose' Dennett means something closer to Aristotelian teleology than theology."--do not fully get to what is at issue. Wright seems to be asking if there is a purpose to life (not in living things). And he argues that complexity and directionality of organisms that flow out of the process of evolution suggests that there is.

So does Dennett for that matter: the only "purpose" of life, in that intentional stance way of speaking, is self-replication. Complexity and directionality follow from self-replication, and the necessary conditions for evolution to get off the ground. That answer seems completely satisfactory to me.

Notice that we can point to ever-greater unintended socio-culture complexity that we can explain game-theoretically with a few elements (iteration, non-zero sumness, cooperative surplus, appropriate discount rates), and not invoke god. Because this complexity happens to be physical, Wright wants to leap to some intelligent designer.

To me the most striking thing about Wright's reasining is this. He suggests, to use your formulation, "[i]f the evolution of life on earth were like the embryological development of individuals, wouldn't that be evidence of Intelligent Design?" Embryological development was the product of a physicalistic process, a blind physicalistic process, evolution. Why, if we want to reason by analogy, should we jump to a non-physical "designer", and an implied "intelligent" one at that? There is a serious question in how a self-replicating unit comes into being, but the leap to god, as Michael Beghe did in Darwin's Black Box, is a strange temptation.

Thanks, Robin. You've given me a lot to think about.

I think Wright is equivocating on "purpose." Even if his argument succeeded, it wouldn't prove nearly as much as theists like Andrew Sullivan would like to think. At best, Wright's argument leaves open the possibility that an Intelligent Designer wanted the natural world to be the way it is. That's always a possible rejoinder. It's not terribly interesting, though. When we talk about the purpose of life, we usually have something loftier in mind. In effect, Wright's argument might show that the ID might have intended purposelessness. (At least purposelessness in a substantive sense.)

It's worth pointing out that Wright does not actually support "Intelligent Design" in the usual anti-Darwinian sense--he believes in evolution by random mutation and natural selection, it's just that he also believes that the laws of nature were tailored to insure that the evolution of life by RM&NS would show a certain kind of directionality. On p. 3 of the beliefnet article, he wrote:

Unlike Dennett and I, Teilhard wasn’t a strict Darwinian; he didn’t believe that nuts-and-bolts natural selection is the sole propulsive force of evolution. And as long as I’m distinguishing myself from others who see the possibility of purpose in evolution: I’m not part of the “intelligent design” school; like Teilhard, intelligent design theorists, such as William Dembski, see forces other than natural selection at work, whereas I’m just saying that natural selection, though able to do all the work of designing organisms, may itself be a product of design.

And this slate article also shows pretty clearly his hostility to "intelligent design theorists":

The "New" Creationism

On the subject of Wright's comparison of the development of life on earth to the development of an embryo, I'll just cut and paste what I wrote in the comments for the Panda's Thumb blog entry on this:

It might help to consider the following speculation. The physicist Lee Smolin has hypothesized that there could be a kind of Darwinian process responsible for setting the values of many constants in physics—his idea is based on the idea from quantum gravity that tiny regions of the universe can pinch off and form a “baby universe” which then expands in a similar way that our own universe expanded after the Big Bang. Smolin suggests that each baby universe might “inherit” similar values of various physical constants as its parent universe, but with slight random variations. He also suggests that baby universes might be formed by the singularity of a black hole, which means the more black holes in a parent universe, the more “offspring” it will have. In this way there would be a sort of process of random mutation and natural selection operating on the scale of universes, with constants that allow for the most black-hole formation being selected for—this would insure, for example, that universes that expand too fast or recollapse too quickly would be selected against, because stars could not form in such universes. Dennett actually discusses this hypothesis in “Darwin’s Dangerous Idea”, I believe.

Suppose we extend this and speculate that any time intelligent life appears in a universe and survives long enough to travel between stars (or creates A.I. ‘children’ that are able to do so), it becomes very likely that they will engage in cosmic engineering projects that result in many more black holes than would have formed naturally (perhaps, for example, the intelligent beings want to maximize the number of computations they’re able to do before the heat death of the universe, and so end up building a lot of black hole computers). In this case, the selection process described by Smolin would also select for values of the constants which increase the probability that intelligent life will form and spread throughout the universe. If there are various typical stumbling blocks along the path to intelligence, like the difficulty of abiogenesis, the difficulty of forming multicellular organisms, and so on, then to the extent that the likelihood of passing these stumbling blocks would be affected by slight variations in the constants of physics (which would surely affect the biochemistry of life in different universes, at least), then the selection process might be able to miminize the chances that a suitable planet will be prevented from giving rise to space-faring intelligence because it hits one of these stumbling blocks.

If all this were true, wouldn’t the analogy to embryology make a fair amount of sense? There are many developmental stumbling blocks that can cause an embryo to die before reaching maturity, but natural selection acts to fine-tune the development process to make it as smooth as possible and to minimize the risk that the embryo will fail in one of these ways. Natural selection acts to insure that the dynamics of the developmental process pull the embryo towards the “attractor” of the adult form, just like the universal natural selection described above would act to insure the dynamics of the biospheres pull them towards the “attractor” of multicellular life with nervous systems of increasing complexity (but note that life in such biospheres would still be evolving in a purely Darwinian way).

The question is, does the development of intelligence in our universe resemble what you’d expect in a universe that had been fine-tuned for it by the Darwinian process described above? My own inclination would be to say no—there’s the Fermi paradox for one thing, and the huge gap between abiogenesis and the development of multicellularity, and I found Robin Hanson’s paper The Great Filter made a good case that the history of life we see on Earth looks just how we should expect if the development of intelligence was in fact very unlikely. On the other hand, if you at least tentatively answer yes, that the history of life on Earth might look about how one would expect if the “universal selection for laws of physics that maximize the probability of spacefaring intelligence” theory were true, then you’ll have to admit that the embryology analogy makes a certain kind of sense. And once you admit that, then you have to admit the possibility that instead of this fine-tuning having been achieved by a selection process, it could have been achieved by a designer who set the laws of physics to maximize the possibility that life would arise and that RM&NS operating on this life over billions of years would lead to the development of intelligence.

Somewhat tangential, as it concerns more evolution, and replicators in general, than any need for considering a higher purpose, but probably worth mentioning since you describe Smolin's ideas about the evolution of a population of universes through black-hole generation and selection: a new class of replicators has apparently been identified with quantum states.

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