You're right, and I won't argue it. The idea of not impossible is one I have difficulty with, though. In my original post, replace <can't drown myself in a bucket of water> with <something my brain won't let me do>, for lack of a better alternative. With anosognosia, that thing is "recognize left-arm paralysis". The reason I didn't stick with that is because I don't know if I have anosognosia or not, which is another layer of uncertainty. Stripped down, though, this is what I'm saying: it seems I should be uncertain about things I know to be certain, and that seems dishonest. I understand the argument against infinite certainty, and that 0 And 1 Are Not Probabilities. Perhaps it's because, as EY suggests, people often say "I can't be certain" simply to establish themselves as rational rather than actually assessing probability. Perhaps it's simply because I dislike an infinitely uncertain universe. Of course, the universe isn't interested in what I like. The map, as ever, is not the territory.