Science used to be defined as "knowledge and the search for understanding of the natural world." In other words, the search for nature's truth, wherever it might lead. Today, however, science is defined in a much more constricted form: "the search for naturalistic explanations of the physical world." The change, of course, was made in order to define the supernatural out of science. How clever those redefiners were. By definition, science excludes creationist theories and intelligent design theories because "they are not science."
That reminds me of the scientist who indulged a similar-pattern question-begging definition when he said something to the effect that "mental states are those thoughts of which we are aware. Therefore, there are no unconscious mental states." Don't like an idea? Just define it out of existence.
And the new definition of science has another benefit. As Philip Johnson has said (in an online lecture), by insisting on natural explanations for everything, an origins model very much like New-Darwinian evolution must be true, since there are no alternatives with any superior probability that involve only naturalistic explanations.
And again, as Philip Johnson points out, that's why examples of mere reversible gene frequencies are touted as evolution, when in fact they show only the flexibility of the genome for horizontal variation. The Galapagos finches, fruit flies, DDT resistant flies, antibiotic-resistant fruit flies, and Kettlewell's Peppered Moths are all examples of reversible variation, not evolution in the sludge to the judge, slime to the sublime sense.
And while I'm haranguing this, let me say I'm very disappointed in the lack of integrity of the whole evolutionary enterprise. Examples: (1) Ernst Haeckel's faked embryos, (2) Kettlewell's faked Peppered Moth photos, (3) the claim that variation is evolution (and the equivocation fallacy involved in trying to confuse the definition of evolution), (4) going to court to prevent criticism of Neo-Darwinism in the public schools, (5) repeating exploded stories like the Stanley Miller "chemicals of life" experiment, and so on, (6) labeling anything not in harmony with the standard model as "pseudoscience," or labeling Intelligent Design as "Intelligent Design Creationism,"
The bottom line is that naturalism is a religion--or, if you prefer, a metaphysical ideology--and, again as has been pointed out numerous times, Neo-Darwinist evolutionary theory is naturalism's creation myth. By defining science down to naturalist philosophy, we have not only a shrunken view of reality, but a Procrustean bed upon which all discoveries in the living (and fossil) world must be forced to fit. Truth? Oh, well, never mind that.