One small, yet profound thing Carl Sagan has contributed to my skepticism was a simple metaphor: The dragon in the garage. This reptilian critter is invisible, incorporeal, breathes heatless fire, and requires no food, air, or water to survive. In short, her existence has no effect on the universe. Because science involves the studying of observable effects, our draconic friend isn't subject to science. Of course, the problem is that without observable effects, it doesn't really matter whether or not she exists:
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. What I'm asking you to do comes down to believing, in the absence of evidence, on my say-so.Woos who use this bit of doggerel don't seem to realize that they're making their woo exactly like the dragon: As powerful as nothing. If something has an effect that can be noticed by a layman, surely it must be subject to science. In addition to making their hypothesis useless, woos make it unfalsifiable: There's nothing it can fail at, because there's nothing it can succeed at, either. No test can be devised for something that does nothing.
I think the problem stems from a fundamental misunderstanding of just what science is. It isn't beakers, X-rays, and so forth: Science can be quite simple, especially when it comes to woo:
The boffins at the Lawrence Livermore Laboratory in California could not explain how an Israeli National managed to levitate a matchbox laid flat on the back of his hand. The physicists had X-rayed the box, looked for magnets, weighed the box to within one micron and analysed the chemical composition of the matches. They found nothing to explain what would make the matchbox stand on its end. When Randi witnessed the phenomenon he was not impressed and immediately replicated the conjuring trick. He placed the matchbox on the back of his hand with the lid slightly ajar, then he closed the box so that some of his skin was jammed in the lid. With a few magical words he suddenly clenched his fist so that the skin on the back of his hand tightened. The matchbox lifted gracefully onto its end. Randi joked that if the fraudster was using supernatural powers to lift the matchbox he was doing it the hard way.A fancy PhD and complicated equipment doesn't make something scientific.