> "A fire-breathing dragon lives in my garage"
> "Show me," you say. I lead you to my garage. You look inside and see a ladder, empty paint cans, an old tricycle--but no dragon.
> "Where's the dragon?" you ask.
> "Oh, she's right here," I reply, waving vaguely. "I neglected to mention that she's an invisible dragon."
> You propose spreading flour on the floor of the garage to capture the dragon's footprints.
> "Good idea," I say, "but this dragon floats in the air."
> Then you'll use an infrared sensor to detect the invisible fire.
> "Good idea, but the invisible fire is also heatless."
> You'll spray-paint the dragon and make her visible.
> "Good idea, but she's an incorporeal dragon and the paint won't stick."
> And so on. I counter every physical test you propose with a special explanation of why it won't work.
> 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.
Currently we don't really understand qualia, but one mainstream theory is that qualia are a different kind of thing to anything else we know about (i.e. are non-physical).
Let's say this theory is true, and, further, that a method for detecting this different kind of thing is detected. That the dragon is invisible, floats, is heatless, is incorporeal, doesn't matter.
The theory that there is a dragon in the garage is falsifiable by the observation that a scan for qualia results negative.
You could say "ah, but this dragon is the dragon of any-test-you-can-come-up-with-doesn't-work, therefore you can't come up with any test which would work". But that would be begging the question.
[1]That is, all animals have qualia.
(I could define myself as an atheist anyway so this is really a non issue for me)
If you've not yet experienced H2G2 I suggest tracking down the original radio version before the books, TV, or more modern film - it is widely available to buy in various formats. It is justly recognized as a classic.