Saturday, February 17, 2007


Out Thinking ID

The National Center for Science Education has pointed out that Elliott Sober's article, "What is wrong with intelligent design?," in Quarterly Review of Biology (March 2007, vol. 82, no. 1, pp. 3-8) is available online in pdf format.

Sober, who holds two chairs in the Department of Philosophy at the University of Wisconsin and who is a renowned philosopher of science, starts by noting that ID is often formulated as a comparatively modest claim (for Constitutional reasons, of course). While Young-Earth Creationism denies common descent or that life on earth is more than 10,000 years old, ID is often stated in a minimalistic form that remains officially neutral on such claims. Sober calls this formulation "mini-ID," which consists solely of the claim that "the complex adaptations that organisms display (e.g., the vertebrate eye) were crafted by an intelligent designer."

While modest in scope, ID advocates hope it will have a large effect by getting into public school science classes and reversing the supposed "stifling dominance of the materialist worldview, and to replace it with a science consonant with Christian and theistic convictions." (Wedge Strategy" available [here])
Sober criticizes the tendency of scientists from Darwin to Gould to object to Intelligent Design (or, in Darwin's case, ID's predecessor, "Natural Theology") on the basis of the bad design that is found in nature. While Sober is correct that the argument that "no designer worth his salt would produce the many imperfect adaptations we observe in nature" fails because it assumes that God would have wanted pandas to have a more efficient device to strip bamboo than a modified sigmoid bone, for example, I think the argument actually goes to the larger issue of God as a designer. After all, what is likely to have more effect on theists who may be toying with adopting ID -- the reams of evidence for evolution or the image of the Discovery Institute actually arguing that an omnipotent and omniscient God ... opps ... "designer," is no better at the job than the guys who designed the Ford Pinto?

The argument from bad design is, to my mind, a theological argument -- but one that goes to why theology should not get involved with empiric investigation of the material universe, rather than an argument about what science can say about God.

That quibble aside, Sober deftly shows why Popper was wrong to think that his criteria of "falsifiability" was the same as "testable" and, therefore, why falsifiability failed as a demarcation criteria between science and pseudoscience. Sober then goes on to develop a different account of testability. First, Sober notes that testing is typically a "comparative enterprise" where one hypothesis is tested against one or more competing hypotheses. But first, they must be shown to actually compete. In other words, the hypotheses must not only make prediction but they must be different and incompatible predictions. But there is a further complication:

As the philosopher Pierre Duhem (1954) emphasized, physical theories, on their own, do not make testable predictions. One needs to add "auxiliary propositions" to the theories one wishes to test. (See the entry on the Duhem–Quine thesis at Wikipedia)
But, in science at least, you can't just invent auxiliary propositions out of thin air.

By inventing assumptions, we can equip a theory with favorable auxiliary propositions that allow it to fit the data. Conversely, a theory also can be equipped with unfavorable auxiliaries that lead it to conflict with the data. An important strategy that scientists use to avoid this nihilistic outcome is to insist that there be independent evidence for the auxiliary propositions that are used.

The auxiliary propositions must be "independently justified" or else we wind up with circular arguments or empty syllogisms where virtually anything and everything can be said to "confirm" our proposition. That's where ID fails:

The important scientific strategy of rendering theories testable by finding independently justified auxiliary propositions does not work for mini-ID. We have no independent evidence concerning which auxiliary propositions about the putative designer’s goals and abilities are true.

Furthermore, Sober shows why, even though Popper's falsifiability criteria itself fails, IDers nonetheless misapply it. Sober points out that IDers who appeal to falsifiability:

... have lost sight of the role of observation in Popper’s concept of falsifiability. For a proposition to be falsifiable, it is not enough that it be inconsistent with a possible state of affairs; it must also be inconsistent with a possible observation. Granted, the ID position is inconsistent with the existence of complex information that never had an intelligent designer in its causal history. It is equally true that "all lightning bolts issue from the hand of Zeus" is inconsistent with there existing even one Zeus-less lightning bolt. These points fail to address how observations could refute either claim.

Sober addresses the claim by ID advocates that criticizing the theory of evolution "tests" ID. Such a claim:

... does nothing to test ID. For ID to be testable, it must make predictions. The fact that a different theory makes a prediction says nothing about whether ID is testable.

IDers who do this have "merely changed the subject."

One good criticism of Behe's "irreducible complexity" argument that Sober points to is:

... his assumption that evolutionary processes must always involve a lockstep increase in fitness. This ignores the fact that contemporary evolutionary theory describes evolution as a probabilistic process. Drift can lead to evolutionary changes that involve no increase in fitness and even to changes that lead fitness to decline. Evolution does not require that each later stage be fitter than its predecessors. At least since the 1930s, biologists have understood that evolution can cross valleys in a fitness landscape.

The most that can be claimed about irreducibly complex adaptations (though this would have to be scrutinized carefully) is that evolutionary theory says that they have low probability. However, that does not justify rejecting evolutionary theory or accepting ID.

The fact that a system can be segmented into n parts in such a way that it counts as irreducibly complex does not guarantee that the evolution of the system involved a stepwise accumulation of parts, moving from 0 to 1 to . . . to n-1 to n parts coming on line. What we call "the parts" may or may not correspond to the historical sequence of accumulating details.

Sober points out that the legs of a horse are "irreducibly complex" because there must be at least three of them (and four is fitter).

So far so good -- the tetrapod arrangement satisfies the definition of irreducible complexity. The mistake comes from thinking that horses (or their ancestors) had to evolve their tetrapod morphology one leg at a time. In fact, the development of legs is not controlled by four sets of genes, one for each leg; rather, there is a single set that controls the development of appendages. A division of a system into parts that entails that the system is irreducibly complex may or may not correspond to the historical sequence of trait configurations through which the lineage passed. This point is obvious with respect to the horse’s four legs, but needs to be borne in mind when other less familiar organic features are considered.

Sober sums up nicely:

It is easy enough to construct a version of ID that accommodates a set of observations already known, but it also is easy to construct a version of ID that conflicts with what we have already observed. Neither undertaking results in substantive science, nor is there any point in constructing a version of ID that is so minimalistic that it fails to say much of anything about what we observe. In all its forms, ID fails to constitute a serious alternative to evolutionary theory.

Highly recommended reading.

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