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)

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 10^150, 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. First, specified complexity, as originally defined by Leslie Orgel, is precisely what Darwinian evolution is proposed to create.

Dembski is said to confuse the issue by using "complex" as most people would use "improbable". He defines CSI as anything with a less than 1 in 10^150 chance of occurring naturally. But this renders the argument a tautology. CSI cannot occur naturally because Dembski has defined it thus, so the real question becomes whether or not CSI actually exists in nature. To demonstrate this, one would need to show that a biological feature really did have an extremely low probability of occurring naturally by any means, an enormously difficult (perhaps impossible) task that would require definitively ruling out all potential theories, including those that may not have been thought of yet. In general, Dembski does not attempt to do this, but instead simply takes the existence of CSI as a given, and then proceeds to argue that it is a reliable indicator of design.

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.

See also

• Intelligent design
• Evolution
• Arguments for the existence of God

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