In answer to an email correspondent:
One of the claims about ID is that it isn't science because it isn't
falsifiable. But is the theory of naturalistic evolution falsifiable, either
conceptually or practically?
Of course, Darwinians would say evolution is falsifiable. But I have at least three problems with that claim:
i) Darwinians have generated many face-saving distinctions and harmonistic devices which can reconcile their theory with opposing lines of evidence, viz. analogy, ancestral homology, derived homology, homoplasy, convergent evolution, parallel evolution, co-option, exaptation, recruitment, evolutionary reversal, &c.
(BTW, I'm pulling these categories from two standard textbooks on evolutionary biology by Mark Ridley and Douglas Futuyma).
In the face of counterevidence, the Darwinian can always add another caveat to his theory.
ii) Given the state of the evidence at any given time, an evolutionary biologist will narrate an evolutionary pathway by which one thing led to another.
When, due to some new scientific development or discovery, the evidence no longer supports that narrative, the evolutionary biologist simply comes up with a new backstory. The theory itself is never challenged. Rather, the backstory is instantly rewritten as necessary to yield the desired result.
iii) Darwinians also rely on circular evidence. Take the following argument:
"The study of phylogeny is really a study of homologous characters. Since all members of a taxon must consist of the descendants of the nearest common ancestor, this common descent can be inferred only by the study of their homologous character. But how do we determine whether or not the characters of two species or higher taxa are homologous? We say that they ware if they conform to the definition of homologous: A feature in two or more taxa is homologous when it is derived from the same (or a corresponding) feature of their nearest common ancestor," Ernest Mayr, What Evolution Is (Basic Books 2001), 16.