Monday, 7 May 2012

Intelligent Design or Interminable Dodging?


To be sure, it is not difficult to find examples of biochemical systems in which the removal of just one part damages the whole system. But consider Behe's phrases "effectively ceases functioning" and "by definition non-functional." There are two possible reconstructions of his definition: 1) the term "functioning" refers exclusively to the basic function currently performed by the whole system (e.g., the rotary motion of the bacterial flagellum) and does not pertain to other possible functions, in other contexts, when one or more components are removed; and 2) the phrases "effectively ceases functioning" and "non- functional" include any function that the impaired system or one of its components may perform in other contexts.
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In fact, only an IC system in the second, strong sense would be an obstacle to evolutionary theory, because it would rule out evolutionary precursor systems and function shifts of the system's components.
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Interestingly, Behe has dis- ingenuously taken advantage of this very ambiguity in answering his critics. In his initial definition, Behe seems to intend the weak interpretation, but he then proceeds to use the concept in a line of reasoning that only makes sense under the strong interpretation.
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Precisely because the bacterial flagellum is IC, Behe tells us, it could not have evolved by means of random mutation and natural selection. However, when critics object that the system's components may well be able to perform other functions in other contexts, thus pointing to the possibility of indirect evolutionary pathways, Behe switches back to the weak definition and claims that his critics have misrepresented his argument.
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Robert Pennock (1999) objected to Behe's design argument that "even if a system is irreducibly complex with respect to one defined basic function, this in no way im- plies that nearby variations might not serve other nearby functions" (p. 267).
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Pennock's reasoning is correct, of course, but in the afterword to the tenth anniversary edition of Darwin's Black Box, Behe (2006) retorts that "Pennock [simply] substituted his own concept of irreducible complexity for mine," whereupon he shifts back to the weak version of the concept, which merely rules out direct improvements on the system: "On the contrary, on page 40, I point out that, although irreducible complexity does rule out direct routes, it does not automatically rule out indirect ones" (p. 258; see also Ratzsch 2005). Thus, Behe protests tiiat Pennock has "overlooked important qualifications" (Behe 2001:707) and has simply "constructed his own rigid straw man defini- tion for IC." But Behe himself has boldly stated that any IC system is a "powerful challenge to Darwinian evolution" (2006:39), and that " [w] e know of no other mechanism, including Darwin's, which produces such complexity" (1996:25). Thus, the fact that Behe's own qualifications are inconsistent with his boastful presentation of IC as a major stumbling block for evolution is hardly Pennock's problem. Behe did acknowledge that Pennock exposed another weakness in the definition of IC, owing to its focus on already functioning systems rather than on the evolutionary development of such systems. Although he promised to "repair this defect in future work" (Behe 2001:695), so far Behe has not lived up to that promise, instead seeming to ignore the problem altogether.




From here:  1. Boudry M, Blancke S, Braeckman J. Irreducible incoherence and intelligent design: a look into the conceptual toolbox of a pseudoscience. The Quarterly review of biology. 2010;85(4):473-82. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21243965.

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