"Creationist critics often charge that evolution cannot be tested, and therefore cannot be viewed as a properly scientific subject at all. This claim is rhetorical nonsense"

This quote by Stephen Jay Gould is describing the criticism of development by creationists. Creationists frequently argue that development can not be checked and therefore can not be thought about a clinical subject. Gould is arguing that this claim is "rhetorical nonsense". He is saying that evolution can be tested and is a valid clinical topic. He is also indicating that creationists are utilizing rhetoric to try and discredit evolution, rather than providing any scientific evidence to support their claims. Gould is asserting that evolution is a legitimate scientific subject and that creationists ought to supply proof to support their claims, rather than depending on rhetoric. He is likewise recommending that creationists must accept the clinical evidence for evolution, instead of trying to discredit it.