Just curious: why did the comment quoted below get down voted? While it may be a bit a bit colorful it raises an issue that is relevant in this case: do we discriminate between evidence a priori?
"Also, remember to apply even standards to evidence. If you flat out deny ufo eye witness accounts as being without epistemic value, also do this for all other eye witness accounts:
Your girlfriend says she saw an eagle over the creek? Didn't happen. And don't investigate any further.
Your friends talk about the beautiful yacht that left the harbor this morning? Flat out deny it. And don't investigate any further.
Your kid eagerly tells you about the squirrel she just saw in the tree outside. Tell her you don't attribute any truth value to her utterings. And don't investigate any further.
If you don't, you have a priori established double standards for the epistemic value of the same type of evidence. This is also known as 'bias'."
This was the follow up comment. Is it too colorful as well?
"The same goes for radar: Today air traffic controllers attribute epistemic value to radar data on the question of determining size and movement of objects in the sky. However, they really should ditch their equipment as we attribute zero epistemic value to the radar signals if the objects it detects move in ways that current man made objects cannot or if the objects are larger than current man made objects (say, with a diameter of two aircraft carriers. Right?"
Recently I've been struck with a belief in Aliens being present on this Earth. It happened after I watched this documenary (and subsequently several others). My feeling of belief is not particular interesting in itself - I could be lunatic or otherwise psychological dysfunctional. What I'm interested in knowing is to what extend other people, who consider themselves rationalists, feel belief in the existence of aliens on this earth, after watching this documentary. Is anyone willing to try and watch it and then report back?
Another question arising in this matter is how to treat evidence of extraordinary things. Should one require 'extraordinary evidence for extraordinary claims'? I somehow feel that this notion is misguided - it discriminates evidence prior to observation. That is not the right time to start discriminating. At most we should ascribe a prior probability of zero and then do some Bayesian updating to get a posterior. Hmm, if no one has seen a black swan and some bayesian thinking person then sees a black swan a) in the distance or b) up front, what will his a posterior probability of the existence of black swans then be?