There's a couple of things I'm willing to assign 100% probability to, in particular something along the lines of "for some reasonably recognizable definition of 'exist', something I can reasonably call 'myself' exists", on the grounds that if I do not in fact exist there's no "my Bayesian probability" to be arguing about in the first place. (It's not quite tautological in the strictest sense, for reasons too long to get into here, but it certainly is close.) So I can't quite go to "impossible". You can't very far on 100%, though; "impossible" is a reasonable approximation.
Oh, and part of my point is that common usage is wrong, on the grounds that the "common usage" is incoherent, meaningless, and information-free. (I basically take it as axiomatic that the worth of the definition of a word can be measured along those axes; I'm generally a descriptive grammarian but that doesn't mean I have to throw all standards out.) Use something more like my definition and you get meaning again.
Oh, and part of my point is that common usage is wrong, on the grounds that the "common usage" is incoherent, meaningless, and information-free. (I basically take it as axiomatic that the worth of the definition of a word can be measured along those axes; I'm generally a descriptive grammarian but that doesn't mean I have to throw all standards out.) Use something more like my definition and you get meaning again.