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The Story of Evolution, Spring 2005
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Leaps of Faith: Accessing Possibilities


Dennett builds a detailed series of images to create the Libraries of Babel and Mendel in order to show the range of possibilities of everything that can exist. His aim is to show that, in order for something to exist, be it an idea or an organism, it must gradually build on all its previous incarnations. However, the implications of Dennett's Library images, as well as the style in which he tells their story, contradict this. In building the complex imagery of the Libraries, Dennett takes various points for granted, moving in leaps of faith rather than the slow and logical steps he argues ideas should take.

The most obvious leap of faith that Dennett takes is one that must be conceded, if the rest of his theory is to be considered. He assumes that the Libraries of Babel and Mendel can exist at all. The Library of Babel supposedly contains all possible books of certain dimensions, regardless of whether or not they have been imagined. This takes for granted that books can be possibilities when they have never been conceived of by their prospective writers, an assumption that Dennett never addresses. However, Dennett deals with the books as books that is, as logical creations based on ideas that are either valid or invalid. If the Library is considered not as a collection of all possible books, but as a collection of all possible combinations of a collection of characters within a given page limit, the idea becomes conceivable. An idea does not have to exist to be possible it just has to be able to be expressed by the given letters within the page limit. This expression of the Library of Babel and by extension, of the Library of Mendel, with nucleotides being substituted for characters is one that Dennett does not explore, though it contains steps necessary for the consideration of his ideas. Dennett's problem is not that he has created an inconceivable idea; it is that he does not express his ideas thoroughly according to the processes he endorses.

After Dennett establishes the idea of the Library of Babel, he extends it to create the Library of Mendel. This idea appears to translate well, since genomes can be written as a combination of four letters, but in his enthusiasm for the idea Dennett does not fully address the problem of applying a literary metaphor to scientific theory. Dennett assumes that the Library of Mendel will include a reader that can interpret all viable genomes, an assumption he does not sufficiently defend. A type of reader for the DNA is necessary, since without readers to interpret it any sequence becomes meaningless. However, just because DNA is read the same way regardless of the type of organism, it does not necessarily follow that the same reader can interpret all viable DNA sequences. Dennett points this out when he mentions that reproducing dinosaurs with Jurassic Park's technology wouldn't work without actual dinosaurs to begin with ((Dennett). 114,) but he never addresses the issue again. Instead, he creates an imaginary DNA reader that can interpret any genome considered viable, to create an organism.

By leaping over a hole in his argument, Dennett does not work within his theory of gradually building on small ideas to create larger ones. To refer to one of his other ideas, Dennett's DNA reader can be viewed as a skyhook, an unsupported image that is vital for the consideration of his argument. The DNA reader is imagined, but there is no reason given for its existence other than to prove Dennett's argument. By not giving more support for his DNA reader, Dennett leaves a gap in the progression of ideas he is trying to create.

Aside from the lack of explanation for this imaginary DNA reader, the idea has another flaw it only interprets the genomes which Dennett considers to be viable. Since it can interpret genomes to create organisms regardless of whether it is scientifically possible, this DNA reader should be able to interpret any genome, even those that appear to be nonsensical. However, Dennett rejects the possibility that either genomes or books can have meaning that is not obvious. He brings up the idea of an imaginary language, which he refers to as Babelish, but he dismisses it without considering the implications ((Dennett). 115.) If it is possible that evolution could have taken different paths than it did, a possibility that Dennett concedes when he refutes determinism and actualism ((Dennett). 120), then it must also be possible that the development of culture could have taken different paths, leading to the development of different languages. The realm of possibility must contain many languages that never had the chance to be created, just as Dennett mentions the books in the Library of Babel that never had the opportunity to be written ((Dennett). 450.) Therefore, some of these books that appear to be incomprehensible may make perfect sense in these possible languages.

Abstract as the concept of possible languages is, it is merely an extension of the theory that all possibilities can be contained within a Library. The interpretation of a sequence, whether it is composed of nucleotides or letters, depends on the language the reader understands. Dennett's imaginary DNA reader only understands genomes that Dennett considers viable. Rather than expressing genomes, it is expressing Dennett's views on which genomes can be created and which are unreadable. This blocks the unfolding of ideas about the realms of possibility. Dennett's argument depends on creating a space in which all possibilities exist, but once he successfully creates it he immediately begins sectioning off some of the possibilities as meaningless. This narrows down the range he must address from all possibilities to merely some, but by doing so Dennett does not fully address the issues he creates.

While creating his image of Libraries of possibilities, Dennett leaves out elements of his ideas that contradict his ultimate point. The Libraries are meant to show that, from a set of all possibilities, ideas and organisms which currently exist built gradually on those which previously existed, without spontaneous occurrences to ease transitions. However, while writing about the Libraries, Dennett makes assumptions to further his argument without sufficiently defending them, following the very pattern that he sets out to discredit.


Dennett) Dennett, Daniel C. Darwin's Dangerous Idea: Evolution and the Meanings of Life. New York: Touchstone, 1995.

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