Extraordinary Claims Require Extraordinary Evidence

[Esquilax]

 Do you think that observation is enough to demonstrate something as possible? Are there things, which must be seen personally to be believed, or can substantiated observation by others be enough? 

Nope. Observation is a necessary, but not sufficient, condition for rationally justified belief. Obviously if you can't observe a phenomena in one way or another you have no way to detect it, but what we also need to recognize is that our observational capabilities are notoriously unreliable on their own; there are plenty of things we can observe that either are not true, in that the true scale of the phenomena is beyond our ability to comprehend personally (think of the flat Earth, revealed to be round when we gain the capacity to increase the scale of our observations) or turn out to have a cause that's different from the one we'd previously come to. Observation helps, but does not on its own demonstrate as much as you'd think. It's step one, really.

I find the demand that unbelievable claims require unbelievable evidence to be outlandish.  So you are going to have to support this with reason and apparently better evidence that an anecdote, about it raining outside (which it's not raining outside, I think I'm going for a cycle ride).

I always find it odd that people make this argument. It's like... do you just think there's no answer to it? Because there is: you can test the efficacy of believing extraordinary claims on mundane evidence as an epistemological method, and see whether those beliefs turn out to be rationally justified or true in the end. From there, you'd have a good relief map of whether believing extraordinary claims on mundane evidence leads to true beliefs or false beliefs, on average. In fact, we already have a sample group for that: it's called all of human history. Our past is rife with people believing extraordinary claims based on mundane phenomena, and uniformly those phenomena have turned out to be, indeed, mundane. Thunder comes from the gods! ... Only no it doesn't, the explanation is mundane. That belief is wrong. Natural disasters are signs that the gods are angry! ... Only no, there's natural explanations for that too, that belief is wrong. Witches! ... Oh wait, not real. Miracles! ... Oh, hold on...

Every single time an extraordinary belief has been proposed on the back of ordinary evidence, that belief has turned out to be wrong, and an ordinary cause has been found. Every. Single. Time. Holding extraordinary beliefs based on mundane evidence has a zero percent success rate, and this is evidence, the best evidence, that holding extraordinary beliefs like that inevitably leads to holding untrue beliefs. That proposed system is ineffective, and that's a trend, no anecdotes required.