The popular defense of intelligent design/creationism (ID) theories, as well as theories in evolutionary biology, especially from the perspective that both are worthy of scientific consideration, is that empirical evidence has been presented that supports both. Both schools of thought have had a tendency to rely on the same class of evidence, namely, the observations of organisms that are in need of being explained by those theories. The result is conflation of the evidence that prompts one to infer hypotheses applying ID or evolutionary theories with the evidence that would be required to critically test those theories. Evidence is discussed in the contexts of inferring theories/hypotheses, suggesting what would be possible tests, and actual testing. These three classes of inference being abduction, deduction, and induction, respectively. Identifying these different inferential processes in evolutionary biology and ID allow for showing that the evidence to which theories and hypotheses provide understanding cannot be the same evidence supporting those theories and hypotheses. This clarification provides a strong criterion for showing the inability of an ID theory to be of utility in the ongoing process of acquiring causal understanding, that is the hallmark of science.Keywords Evolutionary biology Á Intelligent design Á Testability Á Abductive inference Rather than taking on the creationists obliquely and in wholesome fashion by suggesting that what they are doing is 'unscientific' tout court…, we should confront their claims directly and in piecemeal fashion by asking what evidence and arguments can be marshaled for and against each of them….the real question is whether the existing evidence provides stronger arguments for evolutionary theory than for Creationism. Laudan (1982, p. 18)