The dragon in the garage

About this video

"There is a dragon in my garage," says your friend Rosa. You go to look, but the garage is empty. "Oh, I forgot to say: it's invisible." You spread flour on the floor to see its footprints. "It floats in the air." You bring a camera that sees heat, to see its fire. "Its fire is cold." You throw paint over it. "The paint doesn't stick to it." The astronomer Carl Sagan told this story in 1995.

Each time a test could have shown the dragon, Rosa added something new about it, made up just then, just to save the idea from the test, with no other reason to believe it. An addition like that is an excuse: it rescues the idea, but it can't itself be checked. And now ask: what is the difference between an invisible, floating dragon with cold fire that paint doesn't stick to, and no dragon at all? There is none. Nothing you could do would turn out differently. The dragon started as a claim that could be shown wrong, and the excuses turned it into one that can't fail, and so one that says nothing.

Changing an idea after a test isn't always cheating. If Zara's plant didn't bend back towards the window and she said, "maybe most of the light comes from the door", that's fine, because she can close the door and test again. A change that makes a new prediction is a new hypothesis; a change made up only to escape a test is an excuse. So when an idea is rescued, ask: can the rescue itself be tested? This video goes with the An Excuse for Everything lesson of Science Level 1 on Knaph.

Transcript

1. 0:00There's a dragon in my garage.
2. 0:02The garage is empty. Oh, it's invisible.
3. 0:06Flour, for footprints. It floats.
4. 0:10A heat camera. Its fire is cold.
5. 0:14Paint. It doesn't stick.
6. 0:17Now how is that dragon different from no dragon at all? It isn't.
7. 0:23A fair change can be tested. Close the door and try again.
8. 0:29An idea saved by excuses ends up saying nothing.