Specified complexity
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Specified complexity is a concept developed by mathematician, philosopher, and theologian William Dembski. It is commonly presented as part of the critique of natural selection put forward by the intelligent design movement, with which Dembski is associated. The term "specified complexity" was originally coined by origin of life researcher Leslie Orgel, and later employed by physicist Paul Davies in a similar manner, to denote what distinguishes living things from non-living things":
- "In brief, living organisms are distinguished by their ‘’specified‘’ complexity. Crystals are usually taken as the prototypes of simple well-specified structures, because they consist of a very large number of identical molecules packed together in a uniform way. Lumps of granite or random mixtures of polymers are examples of structures that are complex but not specified. The crystals fail to qualify as living because they lack complexity; the mixtures of polymers fail to qualify because they lack specificity." (L. Orgel, The Origins of Life, 1973, p. 189)
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Dembski
Dembski uses specified complexity in a similar manner, to denote a property that makes living things unique. He claims that specified complexity is present when there exists a large amount of specified information. The following examples demonstrate the concept of specified information:.
- High information, low specificity. For example, the 10-letter structure "dkownl el." According to Shannon’s theory of information, a random string of letters contains the highest possible information content, because it cannot be compressed into a smaller string. However, the random nature makes the string without meaning, and thus non-specified according to Dembski. (Note that “meaning” does not play a role in Shannon information theory.)
- High specificity, low information. For example, the 10-letter structure "aaaaaaaaaa." The sequence has low information because it can be compressed into a smaller string, namely “10 a’s” . However, because it conforms to a pattern it is highly specified.
- Specified information. For example, the 10-letter structure "I love you". This has both high information content, because it cannot be compressed, and specificity, because it conforms to a pattern (grammar and syntax). In this case, the pattern it conforms to is that of a meaningful English phrase, one of a selection of strings, which together make up a small fraction of all possible arrangements. In living things, the “pattern” that molecular sequences conform to is that of a functional biological molecule, which make up only a small fraction of all possible molecules.
Dembski defines complex specified information (CSI) as something containing a large amount of specified information, which has a low probability of occurring by chance. He defines this probability as 1 in 10150, which he calls the universal probability bound. Anything below this bound has CSI. The terms "specified complexity" and "complex specified information" are used interchangeably.
Law of Conservation of Information
Dembski and other proponents of ID assert that specified complexity cannot come about by natural means, and is therefore a reliable indicator of design. Dembski has formulated this as his Law of Conservation of Information:
"This strong proscriptive claim, that natural causes can only transmit CSI but never originate it, I call the Law of Conservation of Information.
Immediate corollaries of the proposed law are the following:
(1) The CSI in a closed system of natural causes remains constant or decreases.
(2) CSI cannot be generated spontaneously, originate endogenously or organize itself (as these terms are used in origins-of-life research).
(3) The CSI in a closed system of natural causes either has been in the system eternally or was at some point added exogenously (implying that the system, though now closed, was not always closed).
(4) In particular any closed system of natural causes that is also of finite duration received whatever CSI it contains before it became a closed system."(Intelligent Design: The Bridge Between Science & Theology, InterVarsity Press, 1999, pg. 170)
Critics
The conceptual soundness of Dembski's SC/CSI argument is strongly disputed by critics of ID. They argue that specified complexity, as originally defined by Leslie Orgel, is precisely what Darwinian evolution proposes to create. Namely, selective pressures overwhelmingly operate not on the specific code an organism has, but on the function that code provides in a given environment. Thus probabilistic treatments of that code are irrelevant without considering the transitional nature of the evolutionary process, the fact that later stages are achieved from previous stages. To assume, as Dembski does, that evolutionary assembly is accomplished as a whole is to assume a non-evolutionary premise.
A language analogy is useful: one can communicate "I love you" by saying "I love you" or "I LOVE YOU" or "I <3 U" or "Je t'aime" or any number of methods. In fact, in an environment in which "I love you" is considered to be a default message, no communication at all is needed to convey the intent of the message. The interactions between that which one wishes to communicate, the language or method with which one commuicates, and the interpretations of listeners are similar to natural environments in that language constantly changes and "evolves" to meet the needs of the present. It is for this reason that unused words recede from usage and new ones are coined to meet previously unmet demands on meaning. For example, "Leetspeek" on AOL chatrooms has successfully undermined profanity filters: kids on AOL might understand vulgarity written in language like "ph3aR m3! r0x0rz" but profanity filters do not. Communication is not universally and unchangingly specific; examples of adaptation and evolution in language are commonplace.
The biological analogue of language, i.e. the chemicals, proteins, enzymes, foods, environments, etc. required by life, are not specific, just as the words of language are arbitrary. For example, aerobic organisms by definition need oxygen to live, though there is little specification in general regarding how that oxygen must be supplied. For small aerobic organisms, no real circulation system is required at all, since diffusion works well enough. For larger aerobic organisms, whose inner cells would not receive adequate oxygen via diffusion alone, a circulatory system is needed with special carrier molecules for that oxygen. Though the circulation system is highly complex, it is not in and of itself evidence against evolution. Dembski uses "complex" as most people would use "absurdly improbable," defining CSI as anything with a less than 1 in 10^150 chance of occurring naturally. But this renders his argument a tautology: CSI cannot occur naturally because Dembski has defined it thus. Dembski, to back his claim with evidence, would need to show that a biological feature really did have an extremely low probability of occurring naturally by any means, something which he and others have attempted to do. However since it is difficult to find false-positives or false-negatives, CSI can at most provide a "very high probably" and not absolute conclusion. To this extent Dembski concludes that his anti-evolutionary "design" hypothesis is justified, having shown his example to surpass this simple threshold; hence the tautology.
Theoretical considerations aside, critics cite documented evidence of the kind of evolutionary "spontanteous generation" that Dembski claim's is too improbably to occur naturally. Cheng, in 1998, described the evolution of various antifreeze proteins in diverse animals, one of which was co-opted from a digestive enzyme called trypsinogen. In 1982, Hall demonstrated that after removing a gene that allows sugar digestion in certain bacteria, those bacteria, when grown in media rich in sugar, rapidly evolve new sugar-digesting enzymes to replace those removed.
Calculating the odds for the natural occurrence of a biological structure
Thus far, Dembski has made only one attempt at calculating the odds for the natural occurrence of a biological structure -- the bacterial flagellum of E. coli -- in his book, No Free Lunch. He calculates that the odds of the flagellum originating naturally are below his universal probability bound, but he does so by assuming that all of its constituent parts must have been generated completely at random, a scenario that no biologist would seriously consider. He justifies this approach by appealing to Behe’s concept of "irreducible complexity", which leads him to assume that the flagellum could not come about by any gradual or step-wise process. This could be said to render the validity of Dembski's calculation wholly dependent on Behe’s IC concept. The fact that a plausible model for the evolutionary ascent of the flagellum has been proposed does not bode well for either Behe or Dembski.
See also
External links
- Not a Free Lunch But a Box of Chocolates - A critique of William Dembski's book No Free Lunch by Richard Wein, from TalkOrigins
- Information Theory and Creationism William Dembski by Rich Baldwin, from Information Theory and Creationism, compiled by Ian Reynella
- Critique of No Free Lunch by H. Allen Orr from the Boston Review