Is that true? If we went back in time to before Darwin and gave a not-already-religious person (if we could find one) a thorough rationality lesson — enough to skillfully weigh the probabilities of competing hypotheses (including enough about cognitive science to know why intelligence and intentionality are not black boxes, must carry serious complexity penalties, and need to make specific advance predictions instead of just being invoked as "God wills it" retroactively about only the things that do happen), but not quite enough that they'd end up just inventing the theory of evolution themselves — wouldn't they conclude, even in the absence of any specific alternatives, that design was a non-explanation, a mysterious answer to a mysterious question? And even imagining that we managed to come up with a technical model of an intelligent designer, specifying in advance the structure of its mind and its goal system, could it actually compress the pre-Darwin knowledge about the natural world more than slightly?