I want to start off this post about the classic Carl Sagan quote “extraordinary claims require extraordinary evidence” by thanking Dan, the commenter on my “Sufficient, but not necessary” post, for pointing out that knowledge need not mean absolute certainty, and, quite often, it doesn’t.

This will dovetail into what I’m getting at. Atheism, not being a belief system, but when given at least a little bit of thought, is a result of skepticism and critical thinking. The cornerstone of critical thinking is on how to evaluate claims, as well as the standards we should adhere to when making claims – including the standards we should expect of others when evaluating their claims.

It goes without saying that not every claim is equally incredible. The classic example given for the Sagan quote is “I had a ham sandwich for lunch today”. That’s a great example, but I prefer another one. Suppose I meet with my wife at the end of our work days and she tells me “I had a really shitty day at work”. That’s anything but an extraordinary, outlandish claim. If I demanded from her a battery of evidence to support what she told me, would that be an example of me being a good, skeptical, critical thinker? No! It would make me an asshole. There’s really no reason for me to grill her about it. She’s stating what she feels.

On the other hand, if I tell somebody “I have five naked sorority girls locked in my bedroom closet” with the expectation that people believe me, why should I expect people to take what I say at face value – no questions asked? That is an example of an extraordinary claim, and if I want people to take it seriously, I’d damn well better be able to back it up – with solid evidence.

This same rule should apply to claims people make about a God, whatever name that deity takes, and whatever attributes the claimant ascribes to it. Back to the naked girls scenario – people would dismiss me out of hand if I were to declare that they can’t dismiss my claim out of hand because “you don’t know for sure that I don’t have naked girls in my closet”. So why should claims about Gods, especially claims about Gods that we’d better worship or bad things will happen to us, be held to a different standard? Especially when believers themselves admit that this God can’t be detected using our senses. Something that is undetectable with our senses, even with the technology we have, is indistinguishable from something that doesn’t exist. So, as Dan pointed out in the comments on that earlier blog post, since evidence for a God is sorely lacking, we are more than justified in assuming such a being isn’t real.

The theme “extraordinary claims require extraordinary evidence” doesn’t mean of course that evidence need to lead to absolute certainty. It does mean that for a claim that is, well, extraordinary, that evidence must be testable – that is, independently verifiable, and falsifiable, for starters. At the very least, a sound logical argument is needed to support it.