I’ve been brushing up on the ID stuff recently, given the opening of Expelled, and the discussions that have happened in my post below and also on Michael Behe’s blog in a few of the comment boxes.

Last night I found a very good article by William Dembski that clearly summarizes the ID argument.

He says there are three steps: a logical, an empirical, and an inferential. The logical and empirical steps are negative, and the inferential is positive.

The logical argument is this: irreducibly complex “structures are provably inaccessible to a direct Darwinian pathway.”

The basis for it is the following:

The proof that irreducibly complex systems are inaccessible to direct Darwinian pathways is probabilistic. The proof, though employing logic and mathematics, therefore does not rule out direct Darwinian pathways as a strict logical impossibility. It’s logically possible for just about anything to attain any other thing as a vastly improbable or fortuitous event. For instance, it’s logically possible that a rank chess amateur might stumble upon a series of brilliant moves and thereby defeat the reigning world chess champion in match play. But if that happens, it will be despite the amateur’s limited chess ability and not because of it. Likewise, if a direct Darwinian pathway begets an irreducibly complex biochemical system, then it is despite the intrinsic properties or capacities of the Darwinian mechanism and not because of them. Thus, in saying that irreducibly complex biochemical systems are provably inaccessible to direct Darwinian pathways, design proponents are saying that the Darwinian mechanism has no intrinsic capacity for generating such systems except as vastly improbable or fortuitous events.

The empirical argument is this: “The fact is that for irreducibly complex biochemical systems, no indirect Darwinian pathways are known.” And moreover:

If after repeated attempts looking in all the most promising places you don’t find what you expect to find and if you never had any evidence that the thing you were looking for existed in the first place, then you have reason to think that the thing you are looking for doesn’t exist at all. That’s the argument from irreducible complexity’s point about indirect Darwinian pathways. It’s not just that we don’t know of such a pathway for, say, the bacterial flagellum (the irreducibly complex biochemical machine that has become the mascot of the intelligent design community). It’s that we don’t know of such pathways for any such systems. The absence here is pervasive and systemic. That’s why critics of Darwinism like Franklin Harold and James Shapiro (neither of whom is an intelligent design proponent) argue that positing as-yet undiscovered indirect Darwinian pathways for such systems constitutes “wishful speculations.”

The inference or explanation is the third part of the argument, and it is essentially this: “Scientific explanations come in many forms and guises, but the one thing they cannot afford to be without is causal adequacy. A scientific explanation needs to call upon causal powers sufficient to explain the effect in question,” and thus there needs to be one for the irreducible complexity of certain natural objects. Thus:

when it comes to irreducibly complex biochemical systems, there’s no evidence that material mechanisms are causally adequate to bring them about. But what about intelligence? Intelligence is well known to produce irreducibly complex systems (e.g., humans regularly produce machines that exhibit irreducible complexity). Intelligence is thus known to be causally adequate to bring about irreducible complexity. The argument from irreducible complexity’s explanatory point, therefore, is that on the basis of causal adequacy, intelligent design is a better scientific explanation than the Darwinian mechanism for the irreducible complexity of biochemical systems.

Hope that helps.

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