Faith?

[Ryft]

Arcanus, by your reasoning we cannot say pink unicorns don't exist.

Exactly. This is what it means to be logical or rational, Eilonnwy. You have to look at how the statement ¬P is being supported. A lack of evidence for P ("there are pink unicorns") does not validly establish ¬P ("there are not pink unicorns"), which is precisely what that maxim means: "absence of evidence does not equal evidence of absence." A lack of evidence for P is a good reason to reject P, but is a bad reason to assert ¬P.

Does that mean we should "hold everything as true or possible just because solid evidence for it's non-existence isn't there"? No, for that would simply be the reverse of the very same fallacy! A lack of evidence for ¬P does not establish P, either!

If you search for evidence where there most certainly should be evidence, based on your claim, and then don't find any, I think you're justified in saying something doesn't exist

True. That is establishing evidence of absence (¬P). Now let's look at Sagan's dragon, as per your post (Msg. #22). Tell me what evidence one should expect, given a dragon that is invisible, floating, and transcendent?