eat through

Darwin's Dangerous Idea

Darwin's Dangerous Idea: Evolution and the Meanings of Life (1995) is a controversial book by Daniel Dennett which argues that Darwinian processes are the central organising force in the Universe. Dennett asserts that natural selection is a blind and algorithmic process which is sufficiently powerful to account for the generation and evolution of life including the ins and outs of human minds and societies. These assertions have generated a great deal of debate and discussion within the scientific community.


Dennett's previous book was Consciousness Explained (1991). Dennett noted discomfort with Darwinism among not only lay people but even academics, and decided it was time to write a book dealing with the subject. Darwin's Dangerous Idea is not meant to be a work of science, but an interdisciplinary book; Dennett admits that he doesn't understand all of the scientific details himself. He goes into a moderate level of detail, but leaves it for the reader to go into greater depth if desired, providing plenty of references for this end.

In writing the book, Dennett wanted to "get thinkers in other disciplines to take evolutionary theory seriously, to show them how they have been underestimating it, and to show them why they have been listening to the wrong sirens." To do this he tells a story; one that is mainly original but which includes some material from his previous work.

Dennett taught an undergraduate seminar at Tufts University on Darwin and philsophy, which included most of the ideas in the book. He also had the help of fellow staff and other academics, some of which read drafts of the book. It is dedicated to Van Quine, "teacher and friend".


Part I: Starting in the Middle

"Starting in the Middle", Part I of Darwin's Dangerous Idea, gets its name from a quote by Willard Van Orman Quine: "Analyze theory-building how we will, we all must start in the middle. Our conceptual firsts are middle-sized, middle-distance objects, and our introduction to them and to everything comes midway in the cultural evolution of the race."

The first chapter "Tell Me Why" is named after a song.

Before Charles Darwin, God was seen as the ultimate cause of all design, or the ultimate answer to 'why?' questions. John Locke argued for the primacy of mind before matter, and David Hume, while exposing problems with Locke's view, could not see any alternative.

Darwin provided just such an alternative: evolution. Besides providing evidence of common descent, he introduced a mechanism to explain it: natural selection. According to Dennett, natural selection is a mindless, mechanical and algorithmic process—Darwin's dangerous idea. The third chapter introduces the concept of "skyhooks" and "cranes" (see below). He suggests that resistance to Darwinism is based on a desire for skyhooks, which do not really exist. According to Dennett, good reductionists explain apparent design without skyhooks; greedy reductionists try to explain it without cranes.

Chapter 4 looks at the tree of life, such as how it can be visualized and some crucial events in life's history. The next chapter concerns the possible and the actual, using the 'Library of Mendel' (the space of all logically possible genomes) as a conceptual aid.

In the last chapter of part I, Dennett treats human artifacts and culture as a branch of a unified Design Space. Descent or homology can be detected by shared design features that would be Vastly unlikely to appear independently. However, there are also "forced moves" or "good tricks" that will be discovered repeatedly, either by natural selection (see convergent evolution) or human investigation.

Part II: Darwinian Thinking in Biology

The first chapter of part II, "Darwinian Thinking in Biology", asserts that life originated without any skyhooks, and the orderly world we know is the result of a blind and undirected shuffle through chaos.

The eighth chapter's message is conveyed by its title, "Biology is Engineering"; biology is the study of design, function, construction and operation. However, there are some important differences between biology and engineering. Related to the engineering concept of optimization, the next chapter deals with adaptationism, which Dennett endorses, calling Gould and Lewontin's "refution" of it an illusion. Dennett thinks adaptationism is, in fact, the best way of uncovering constraints.

The tenth chapter, entitled "Bully for Brontosaurus", is an extended critique of Stephen Jay Gould, who Dennett feels has created a distored view of evolution with his popular writings; his "self-styled revolutions" against adaptationism, gradualism and other orthodox Darwinism all being false alarms. The final chapter of part II dismisses directed mutation, the inheritance of acquired traits and Teilhard's "Omega-point", and insists that other controversies and hypotheses (like the unit of selection and Panspermia) have no dire consequences for orthodox Darwinism.

Part III: Mind, Meaning, Mathematics and Morality

"Mind, Meaning, Mathematics and Morality" is the name of Part III, which begins with a quote from Nietzsche. Chapter 12, "The Cranes of Culture", discusses cultural evolution. It asserts that the meme has a role to play in our understanding of culture, and that it allows humans, alone among animals, to "transcend" our selfish genes. "Losing Our Minds to Darwin" follows, a chapter about the evolution of brains, minds and language. Dennett criticizes Noam Chomsky's perceived resistance to the evolution of language, its modeling by artificial intelligence, and reverse engineering.

The evolution of meaning is then discussed, and Dennett uses a series of thought experiments to persuade the reader that meaning is the product of meangingless, algorithmic process.

Chapter 15 asserts that Gödel's Theorem does not make certain sorts of artificial intelligence impossible. Dennett extends his criticism to Roger Penrose. The subject then moves on to the origin and evolution of morality, beginning with Thomas Hobbes (who Dennett calls "the first sociobiologist") and Friedrich Nietzsche. He concludes that only an evolutionary analysis of ethics makes sense, though he cautions against some varieties of 'greedy ethical reductionism'. Before moving to the next chapter, he discusses some sociobiology controversies.

The penultimate chapter, entitled "Redesigning Morality", begins by asking if ethics can be 'naturalized'. Dennett does not believe there is much hope of discovering an algorithm for doing the right thing, but expresses optimism in our ability to design and redesign our approach to moral problems. In "The Future of an Idea", the book's last chapter, Dennett praises biodiversity, including cultural diversity, but does not extend this praise to religious fundamentalism. In closing, he uses Beauty and the Beast as an analogy; although Darwin's idea may seem dangerous, it is actually quite beautiful.

Central concepts

Natural selection as an algorithm

Dennett describes natural selection as a substrate-neutral, mindless algorithm for moving through "Design Space".

Universal acid

Dennett writes about the fantasy of a “universal acid” as a liquid that is so corrosive that it would eat through anything that it came into contact with, even a potential container. Such a powerful substance would transform everything it was applied to; leaving something very different in its wake. This is where Dennett draws parallels from the “universal acid” to Darwin’s idea:
“it eats through just about every traditional concept, and leaves in its wake a revolutionized world-view, with most of the old landmarks still recognizable, but transformed in fundamental ways.”
While there are people who would like to see Darwin’s idea contained within the field of biology, Dennett asserts that this dangerous idea inevitably “leaks” out to transform other fields as well.

Skyhooks and cranes

Dennett used the term "skyhook" to describe a source of design complexity that did not build on lower, simpler layers - in simple terms, a miracle.

In philosophical arguments concerning the reducibility (or otherwise) of the human mind, Dennett's concept pokes fun at the idea of intelligent design emanating from on high, either originating from God, or providing its own grounds in an absurd, Münchhausen-like bootstrapping manner.

Dennett also accuses various competing neo-Darwinian ideas of making use of such supposedly unscientific skyhooks in explaining evolution, coming down particularly hard on the ideas of Stephen Jay Gould.

Dennett contrasts theories of complexity which require such miracles with those based on "cranes", structures which permit the construction of entities of greater complexity but which are themselves founded solidly "on the ground" of physical science.


In the New York Review of Books, John Maynard Smith gave praise for Darwin's Dangerous Idea:

"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…"

In the New York Review of Books, Stephen Jay Gould criticised Darwin's Dangerous Idea for being an "influential but misguided ultra-Darwinian manifesto".

"Daniel Dennett devotes the longest chapter in Darwin's Dangerous Idea to an excoriating caricature of my ideas, all in order to bolster his defense of Darwinian fundamentalism. If an argued case can be discerned at all amid the slurs and sneers, it would have to be described as an effort to claim that I have, thanks to some literary skill, tried to raise a few piddling, insignificant, and basically conventional ideas to "revolutionary" status, challenging what he takes to be the true Darwinian scripture. Since Dennett shows so little understanding of evolutionary theory beyond natural selection, his critique of my work amounts to little more than sniping at false targets of his own construction. He never deals with my ideas as such, but proceeds by hint, innuendo, false attribution, and error."

Gould was also a harsh criticizer of Dennett's idea of the "universal acid" of natural selection and of his subscription to the idea of memetics.

Dennett's response and an exchange between Dennett, Gould, and Robert Wright can be found here.

Biologist H. Allen Orr wrote a scathing review emphasizing similar points in the Boston Review, to which Dennett later responded.

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