Darwin's Dangerous Idea: Evolution and the Meanings of Life
As an evolutionary biologist, I am used to being misunderstood by philosophers. Even my favorite philosopher, Karl Popper, although he later repented, argued for many years that evolution theory is metaphysics rather than science. It is therefore a pleasure to meet a philosopher who understands what Darwinism is about, and approves of it.
Dennett goes well beyond biology. He sees Darwinism as a corrosive acid, capable of dissolving our earlier belief and forcing a reconsideration of much of sociology and philosophy. Although modestly written, this is not a modest book. Dennett argues that, if we understand Darwin’s dangerous idea, we are forced to reject or modify much of our current intellectual baggage—for example, the ideas of Stephen Jay Gould, Noam Chomsky, Jerry Fodor, John Searle, E.O. Wilson, and Roger Penrose. As it happens, he is not the first to see how farreaching are the effects of Darwin’s idea. Darwin himself wrote, “He who understands baboon would do more toward metaphysics than Locke.” It is a remarkable fact that these words were written in a private notebook when Darwin was still seeking a theory of evolution.
Dennett’s central thesis is that evolution by natural selection is an algorithmic process. An algorithm is defined in the OED as “a procedure or set of rules for calculation and problem-solving.” The rules must be so simple and precise that it does not matter whether they are carried out by a machine or an intelligent agent; the results will be the same. He emphasizes three features of an algorithmic process. First, “substrate neutrality”: arithmetic can be performed with pencil and paper, a calculator made of gear wheels or transistors, or even, as was hilariously demonstrated at an open day at my son’s school, jets of water. It is the logic that matters, not the material substrate. Second, mindlessness: each step in the process is so simple that it can be carried out by an idiot or a cogwhell. Third, guaranteed results: whatever it is that an algorithm does, it does every time (although, as Dennett emphasizes, an algorithm can incorporate random processes, and so can generate unpredictable results).
How can it be that such a mindless process can generate such wonderful results? In particular, how can it have produced us? Before Darwin, it was the accepted opinion of both philosophers and biologists that the complex adaptations of living things implied an intelligent designer. The essence of Darwin’s dangerous idea is that adaptations can arise by natural selection, without need of intelligence: that is, they can be the products of an algorithmic process. Dennett repeatedly uses the analogy of “cranes” and “skyhooks.” These are both devices for lifting things—in evolution, for generating increasingly complex designs—but of very different kinds. A crane is a structure or process which is itself the product of the natural selection of replicating entities, but which, once it has arisen, makes it possible for still more complex structures to evolve.
Two examples will make the point clearer. The first populations of…
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