Johnson argues. It forces biologists to accept even weak theories so long as they are naturalistic. Darwinism itself is the prime example. Observational evidence cited for Darwinism consists of minor variations, akin to those routinely produced by farmers and breeders. For example, in a New York Times article, Jonathan Weiner describes a study of Darwin's famous finches: The finches' beaks grew larger in dry seasons, when the seeds they eat were tough and hard, but grew smaller again after a rainy season, when tiny seeds became available once more. This is evolution happening "before [our] very eyes," Weiner writes.
But as Johnson points out, it is precisely the opposite. The change in finch beaks, he argues, is a minor, cyclical fluctuation that allows the finches to adapt and survive. Translation: It's a small adjustment that allow finches to stay finches. It does not demonstrate that finches are evolving into another kind of bird, nor that they evolved originally from another kind of organism. It's odd that a mechanism permitting an organism's major features to remain unchanged should be cited as evidence for a theory of limitless change.
Moreover, the naturalistic assumption compels biologists to ignore the overwhelming evidence for purpose and design that can be read right off the face of nature. It seems intuitively obvious that eyes are designed for seeing, ears for hearing, and fins for swimming. Even dyed-in-the- wool atheists such as Dawkins acknowledge the prima facie evidence of purpose: his definition of biology is "the study of complicated things that give the appearance of having been designed for a purpose." The goal of Darwinism is to demonstrate that, contrary to appearances, these complicated things are really the product of random changes and natural laws.
But a century and a half after Darwin, that goal has not been reached. (The scientific failures of Darwinism are discussed at length in Johnson's first book, Darwin on Trial, and outlined only briefly here.) The meager factual basis for Darwinism makes plausible Johnson's thesis that the major reason for the theory's dominance is not science but philosophy: It reassures secularists that they don't have to worry about a Creator.