So yes, my arguments might give us reason to prefer natural explanations when these are available, and to seek natural explanations when they are not. It follows that a proposed theistic explanation should be, at best, an explanation of last resort. One might argue that this view — that we should abandon the search for natural explanations only in extremis — represents a kind of “presumption of naturalism.” And so it does. ¶ My own view is that the naturalistic research tradition of the sciences has been stunningly successful and must rank as one of the greatest of human achievements. But I think it is poorly served by attempts to define science in such a way as to exclude the supernatural. The debate over intelligent design is instructive in this regard. One might win a legal victory by insisting that this proposed theistic explanation is not what we customarily call “science.” And this is true, for contingent historical reasons. But it would be much more effective to show that this particular proposed theistic explanation, with its deliberately vague appeal to an unspecified “designer,” is practically vacuous. it lacks the first and most important virtue of any proposed explanation, namely that of testability. It follows that this particular proposed theistic explanation should be rejected. ¶ Could the theist produce a better one? I doubt it, but then it would be most regrettable if we were to forbid him to try. Nothing could be more antithetical to the spirit of free enquiry than this kind of censorship. If proposed theistic explanations are to be defeated, as they have been so often in the past, it will be by way of the free contest of ideas.