Posted: Apr 16, 2014 2:29 pm
Consider generalised "psi" claims as mentioned in the article, people have been looking for them for literally hundreds of years. Millions of papers have been written on the subject and yet never has the phenomenon been found. If it exists, it becomes ever more unlikely that we could observe this state of affairs. The level of certainty grows with each failure in proportion to the chance the test would have found evidence if the phenomenon was real.
In other cases it is legitimate to take a probability of 0 as as starting point, if someone guessed the exact number of stellar bodies in the observable universe without any form of reasoning or calculation the chance they get it right is vanishingly small (due to the large number of possibilities) in unrestricted cases where drawing from infinite sets the probability is actually 0.
My point is that active disbelief (as opposed to merely withholding belief) is usually justified in the situations where people apply it, even if the reasons aren't always articulated. There are of course situations in which disbelief is not justified e.g. if someone claims that there is life somewhere outside our solar system, since we know that life is possible but we have absolutely no means of assigning probabilities within the small finite set (only two options - there is or there isn't).
In other cases it is legitimate to take a probability of 0 as as starting point, if someone guessed the exact number of stellar bodies in the observable universe without any form of reasoning or calculation the chance they get it right is vanishingly small (due to the large number of possibilities) in unrestricted cases where drawing from infinite sets the probability is actually 0.
My point is that active disbelief (as opposed to merely withholding belief) is usually justified in the situations where people apply it, even if the reasons aren't always articulated. There are of course situations in which disbelief is not justified e.g. if someone claims that there is life somewhere outside our solar system, since we know that life is possible but we have absolutely no means of assigning probabilities within the small finite set (only two options - there is or there isn't).