Darwin's Dangerous Idea: Evolution and the Meanings of Life. - book reviews

National Review, May 15, 1995 by John Polkinghorne

Darwin's Dangerous Idea: Evolution and the Meanings of Life, by Daniel C. Dennett (Simon & Schuster, 586 pp., $30)

Rev. Dr. John Polkinghorne is the president of Queens' College, Cambridge. His Gifford Lectures are published by Princeton as The Faith of a Physicist.

IT IS the season, it seems, for Astonishing Hypotheses and Dangerous Ideas, notions claimed to be at once so simple and so powerful that they yield accessible solutions to the problems that have plagued human thought for many centuries. At last it can be told -- or that is what the proponents declare to us.

Daniel Dennett's version of this philosophical nostrum is one that has been around for quite a while. It is none other than the Darwinian idea of the evolution of complexity through the process of natural selection. It is presented to us, not as an outstanding insight into the biological history of the development of life, but as the answer to practically any question. "Darwin's dangerous idea is reductionism incarnate, promising to unite and explain just about everything in one magnificent vision."

"Darwin's dangerous idea is reductionism incarnate, promising to unite and explain just about everything in one magnificent vision."

There is something fishy about these proffered intellectual passkeys that turn every lock. Even in physics, grand unified theories are very hard to find, and it surely cannot be easier to discover them in the much broader realm of inquiry that we might call metaphysics. Of course, there is something in the insights thus offered; it is simply the claim of their omnicompetence that looks like overkill. Characteristically, such schemes present a simple and appealing pattern of explanation which seems flexible enough to fit many cases. Evolution through the competition to survive is like that; so is the Hegelian dialectic of thesis and antithesis leading to synthesis. Once one has got the hang of such a pattern, it is rather easy to twist things into that pleasing shape. Once one knows that survival value is the key, then of course there must be a lot of survival value around. Ideas become self-fulfilling. This leads to those conjectured tales which Stephen Jay Gould has rightly described as Just So Stories. They are similar to the way in which simple-minded religious believers tell pious tales to the effect that all that happens is absolutely, and in an unqualified way, for the best. The real world is more complicated, perplexing, and interesting than any of these facile accounts.

Dennett is far too clever to fall for the grosser forms of reductionism. He calls them "greedy reductionism" and chides the likes of B. F. Skinner and Edward O. Wilson for being too crude in their attempts at explanation. His own reductionism is much more sophisticated. One of Dennett's gifts is the ability to invent lively and tendentious terminology and stories in order to back up his line of argument. He characterizes the battle over reductionism as being "cranes" versus "skyhooks." The cranes are built from below and they represent the complexity and novelty that arise from the interplay of constituent bits and pieces, the combined effects of many elementary events. The skyhooks are to do duty as representatives of organizing principles or acts of a holistic character, whose nature and consequences will not be discernible if we restrict ourselves to a reductionist account. Of course the name is chosen to suggest that such top-down concepts are of an implausible or frankly fabulous character. "Skyhooks are miraculous lifters, unsupported and insupportable. Cranes are no less excellent as lifters, and they have the decided advantage of being real." This is clever debating technique but it is not the way to settle a serious issue. Skyhooks are not as unanchored as Dennett would have us think.

One of the serious questions that many physical scientists wish to ask about a purely Darwinian account of the evolution of life is whether there has been adequate time available to accommodate the amazing variety and complexity of change involved. Three to four billion years may seem a long period, but astonishing things have to have happened, not least in the rapid development of the hominid brain in the space of only a few million years. Is the patient accumulation and sifting of small genetic differences sufficient to accomplish this? Those who ask the question are not querying the idea that natural selection has a role to play, but they simply ask whether it is by itself totally adequate as an explanation. The questioners are not looking for a gap into which to insert the finger of divine intervention, but they may just be seeking a more comprehensive and persuasive scientific account. People like Paul Davies (The Cosmic Blueprint) are very impressed with the remarkable drive to complexity present in cosmic history. Dennett occasionally refers to this time-scale problem, but it seems that neither he nor any other evolutionary reductionist is able to offer a convincing answer to it.