alt Hacker News> The dragon in the room is the hidden qualifier for "undetectable by any means" is "that is currently known to humanity".
> That makes Carl Sagan's claim some what Balonish. Not sure why the smart Sagan fell for it.
The point is that if someone does claim that the dragon exists, they better be able to explain how they know it exists.
Subjective experience.
Imagine you are a pigeon with navigation magnets in your head. And imagine asked by your friends without it "How do you know it is the right direction?", at some point you have to say "I just know it dammit!"
And imagine pigeons haven't yet figured out magnetism. So it ain't possible to explain it by any means known to them.
Carl sagan's logic breaks down at this point.