Sagan's wet candle

Now, what's the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all?  If there's no way to disprove my contention, no conceivable experiment that would count against it, what does it mean to say that my dragon exists?  Your inability to invalidate my hypothesis is not at all the same thing as proving it true.  Claims that cannot be tested, assertions immune to disproof are veridically worthless, whatever value they may have in inspiring us or in exciting our sense of wonder. Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark (Ballantine 1997), 171. 

That's Sagan's uncredited knockoff on parables by John Wisdom and Antony Flew. I've commented on this before, but since it cropped up again, I'll revisit the issue.

This is Sagan's attempt to debunk the supernatural and paranormal. But there are several problems with his comparison:

i)  In medieval lore, dragons are part of the natural world. Yet dragon's are naturally impossible. It's naturally impossible for an animal that size to fly. It's naturally impossible for an organism composed of protoplasm to generate and exhale fire. That, in itself, is a reason to discount their existence.

ii) If they did exist, dragons are supposed to be physical, empirical objects. So they're supposed to be detectable in principle. Therefore, Sagan's thought-experiment artificially redefines the concept.

iii) The problem with Sagan's comparison is that he acts as though there's no evidence for supernatural or paranormal reports, so it's a matter of concocting face-saving explanations to account for the lack of evidence. But that's a straw man. There is prima facie evidence for certain kinds of paranormal or supernatural phenomenon. So the real question at issue is not the absence of evidence but whether the prima facie evidence is defective. 

iv) The fact that there's no Aston Martin DB5 in my garage doesn't imply or presume that there's no Aston Martin DB5 in your garage. If, moreover, when I peer into your garage, I sometimes see an Aston Martin DB5 but at other times the garage is empty doesn't mean the misses cancel out the hits. Likewise, the absence of miraculous healings or answered prayer in some cases doesn't cancel out the evidence for miraculous healings or answered prayer in other cases.