It science, it is reasonable to search for naturalistic explanations. After all, if we assumed lightening bolts came from zeus and the sun was pulled in a chariot, our knowledge would be limited indeed. So if it is appropriate to search for natual explanations, then is it ever appropriate to look for a supernatural explanation? Sure. If one can exhaust all of the possible natural explantions, then only supernatural explanations make sense. But here's the rub. One can only exhaust all possible natural explanations if one has perfect knowledge of the natural world. Otherwise, the possibility remains that there is a natural explanation you have not considered. So, to assume intelligent design, a supernatural cause, one must also assume that for the case in question, no natural explanation is or can ever be possible. And for one to make such a claim with logical integrity, one must possess perfect knowledge of the natural world. Science makes no claim to perfect knowledge of the natural world. Indeed, if perfect knowledge of the natural were to be obtained, then science would cease to be necessary.