Well, yes, the statement "I'm not a witch" is of zero information value. It's ridiculous to conclude "That's exactly what a witch would say, therefore I believe more that you are a witch", but it's equally ridiculous to conclude "That's exactly what a non-witch would say, therefore I believe more that you aren't a witch." You should not have your beliefs changed at all by the fact that someone claims not to be a witch (unless you believe that witches are unwilling to lie, or something).
I'm trying to figure out if this response is similarly of zero information value - interesting, but should not convince me either that he's in the right or that he's in the wrong - or of nonzero information value, convincing me that he's in the right. I'm currently leaning towards the former.
I'm trying to figure out if this response is similarly of zero information value - interesting, but should not convince me either that he's in the right or that he's in the wrong - or of nonzero information value, convincing me that he's in the right. I'm currently leaning towards the former.