Intelligent design ducks the rigors of science.
Intelligent design ducks the rigors of science.
Science, technology, and life.
Sept. 29 2005 7:30 AM

Grow Some Testables

Intelligent design ducks the rigors of science.

Four months ago, when evolution and "intelligent design" (ID) squared off in Kansas, I defended ID as a more evolved version of creationism. ID posits that complex systems in nature must have been designed by an intelligent agent. The crucial step forward is ID's concession that "observation, hypothesis testing, measurement, experimentation, logical argument and theory building"—not scriptural authority—define science. Having acknowledged that standard, advocates of ID must now demonstrate how hypotheses based on it can be tested by experiment or observation. Otherwise, ID isn't science.

This week, ID is on trial again in Pennsylvania. And so far, its proponents aren't taking the experimental test they accepted in Kansas. They're ducking it.

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.


The Pennsylvania case involves a policy, adopted by the board of the Dover Area School District, that requires ninth-grade biology teachers to tell students about ID. According to the policy, "A theory is defined as a well-tested explanation that unifies a broad range of observations." So far, so good.

Under the policy, "Students will be made aware of gaps/problems in Darwin's Theory and of other theories of evolution including, but not limited to, Intelligent Design." Notice the "of" before "other theories." The policy doesn't tell teachers to discuss gaps and problems in ID. It tells them to discuss gaps and problems in Darwinism—and then to discuss ID as an alternative "theory." The board's brief makes clear that the policy's aim is "informing students about the existing scientific controversy surrounding Darwin's Theory of Evolution, including the fact that there are alternative scientific theories."

The first half makes sense: Students should be made aware of gaps and problems in Darwinism. But what's with the second half? Once you've outlined the limits of Darwinism, what more does ID offer? What does it say? What does it explain?

So far, nothing.

The board names two scientists who advocate ID "as a scientific theory": Michael Behe of Lehigh University and Scott Minnich of the University of Idaho *. Minnich's expert testimony in the Dover case refers to Behe's work. Behe's testimony refers to a 2001 article in which he claims to have shown "that intelligent design theory is falsifiable." A longer version of the article explains,

In fact, intelligent design is open to direct experimental rebuttal. Here is a thought experiment that makes the point clear. In Darwin's Black Box (Behe 1996) I claimed that the bacterial flagellum was irreducibly complex and so required deliberate intelligent design. The flip side of this claim is that the flagellum can't be produced by natural selection acting on random mutation, or any other unintelligent process. To falsify such a claim, a scientist could go into the laboratory, place a bacterial species lacking a flagellum under some selective pressure (for mobility, say), grow it for ten thousand generations, and see if a flagellum—or any equally complex system—was produced. If that happened, my claims would be neatly disproven.

Behe is right that such an experiment, by showing that random mutation and natural selection can produce the flagellum, would disprove the claim that they can't. He calls the latter claim—that Darwinism fails to produce the flagellum—the "flip side" of his claim that the flagellum required intelligent design. But the Darwinism-fails claim isn't just the "flip side" of the design-is-necessary claim. It's the whole thing. The theory that's being tested in the experiment is Darwinism. If Darwinism succeeds, ID would be disproved, but only to the extent that ID consists of saying Darwinism would fail. And to that extent, ID isn't an explanatory theory in its own right. It's just a restatement of the first half of the Dover School Board's policy: a discussion of gaps in Darwinism.

Behe's article makes clear that ID is purely negative, with no explanatory mechanisms of its own.

  Slate Plus
Year of Great Books
Feb. 8 2016 1:57 PM The Man From Uncle In Praise of Uncle Toby, the Warm Beating Heart of Tristram Shandy.