Thread: Can someone explain the usage of the phrase "Extraordinary claims require extraordinary evidence"?

There is nothing subjective at all about it. For a claim to be "extraordinary", it must have a probability based on our current state of knowledge of below 1%. This can all be formalized with statistical methods. Just because a phrase uses qualitative language like "extraordinary" does not mean it has no quantitative basis and attempting to reject it sounds like it's more motivated by ideologies that can't stand up to scrutiny then a genuine argument for tabooing it.

Edit:
I feel like I should qualify what "current state of knowledge" entails. It's in essence the set of all beliefs held by the subject. Each belief has a percentage bound to it.

So, for example: I am 80% sure that Sally likes me. Now if I encounter a situation where she does not respond to my greeting on the street, that will downgrade my certainty by a certain percentage. However a key factor her is that it is not an on/off switch. Let's say I am 60% sure now that she likes me. Perhaps she was in deep thought or simply did not hear me.

Now let's say that this situation happens over and over again, now my confidence that Sally likes me is 30% or so. However, it can never drop to zero. There is always a chance that new evidence will come in that will bolster the likelihood up to maybe 40% or eventually to 80% again.

An extraordinary claim like telepathy has a likelihood of below 1%. This does not mean it is impossible but it does mean that it is worth proportionally less of your time investigating and that the burden of providing proof should be on the agent that is claiming as opposed to yourself. That is why it is in fact virtuous to refuse to investigate some things that fall below a certain point of likelihood. Your time is precious and you are not obliged to entertain a concept that is absurd from your reference frame.