Ok, I don't believe in p-zombies, in the standard sense of there being a logically possible world which is physically identical to this one, but where the inhabitants are not conscious. But I do believe that someone (perhaps a super-intelligent being) could possibly emulate my outward behavior perfectly, while having very different conscious experiences on the inside (i.e., by lying). I don't think you can distinguish between these two cases without reference to what I'm really experiencing, as opposed to just what I say about what I experience.