The explanatory filter sifts through three possible explanations for the existence of a particular phenomenon: a regular feature of some well known natural law, chance, and design. If the researcher can eliminate regularity and chance as explanations, that leaves only design. In the presence of what is apparently complex, useful design in organisms, we are to assume the existence of some sort of designer. Hence Intelligent Design.
Dembski uses this argument to show that the “fine-tuning” of the fundamental constants of the universe and the existence of irreducibly complex organelles in the body indicate the existence of true design, and therefore, the Designer’s existence is proven, Q.E.D.
Dembski also seeks to use ID to explain the growth of information in Earth’s biosphere over time. Information is depicted as that which only can be produced by intelligence. How can usable information increase without an intelligent producer of that information? This is merely a new twist on the old creationist question, “How can there be design without a Designer?”
ID has some useful socio-political aspects. It has the potential to break what creationists see as a stranglehold of secular humanism over American science and education.
ID also eases the way for theology. It gives religious believers comfort by supporting creationists’ assertions about God’s creative power, avoiding the perceived purposeless of life, and anarchy they believe grow out of non-belief and philosophical materialism.
A creationist expressed this sentiment in a very moving way. He was quoted by Kenneth Miller, “I felt again the warmth of believing that for every inch of infinity there has already been an accounting. Everything has a reason for being where it is… I had felt it before in childhood, when everything around me radiated with specific meaning and parental clarity. That, after all, is what creationists feel that evolution has stolen from them.” (3)
As you may imagine, Humanists have many problems with ID. For instance, Behe’s irreducible complexity fails to consider alternative hypotheses for the very complex systems found in cells. First, the intermediate stages in the development of what is now irreducible, may have once served other functions. Biologists call that “evolutionary cooptation.” Second, slight modifications in the components may not damage the irreducibly complex system. Third, the interstages may also have included previously useful, non-irreducible complex components, which later were dropped by the system when they lost their usefulness—a kind of biological scaffolding disassembled when no longer in use. We are just at the beginning of learning to understand the molecular systems Behe describes so well in his book. It’s way too early to write off evolutionary explanations of their existence.
Evolution does work on molecular systems: scientists have tested natural selection on the molecular level by breaking a piece off a human growth hormone receptor, then randomly mutating the hormone “key.” Miller describes how effective the random mutation strategy was in this experiment. “It generated a new version of the hormone that fit the new receptor 100 times tighter than the nonmutant version.” (4)
The same problems with Johnson’s analysis of evolutionary theory can be seen in all his books. He bases his case almost entirely on what Miller calls, “the argument from personal incredulity.” (5) Against the mountains of evidence for the existence of natural selection in nature, he continually insists on more, more, more! He is not convinced, and so his legal training leads him inevitably to “reasonable doubt.” But, since he doesn’t have the necessary scientific training, he’s incapable of going beyond doubt to the development of serious scientific objections to evolution.
Dembski’s explanatory filter leaves out a fourth, very powerful explanation for the existence of complex entities: Unguided, unplanned selection working on genetic variety. Nature is fecund. Most organisms don’t have a chance to pass on their genetic inheritance to descendants. Thus, selection always takes place, by definition must take place, and it attains its own powerfully catalytic direction without any intended design whatsoever.
Gene duplication and modification adds to the biosphere naturally. To Dembski’s charge that mutation just changes DNA nucleotides and doesn’t add anything, may I point out that there are several ways in which DNA can add information over the generations? One is by replicating previously existing genes on the same strand of DNA, then permitting these copies to diverge from the original over many succeeding generations. We see convincing evidence for this in the human genome. It’s loaded with duplicate genes. After many additional iterations of such duplication, the information load can greatly increase in the genome.