This is an interesting thought experiment I've come across recently. If you lost all your senses - sight, hearing, smell and what have you, would you still know if you existed? Well, the answer is yes. Even if I can't sense anything outside my body, I can still sense my body in certain ways. I can feel physical exertion, I can sense if I am upright or otherwise and so on. Now what if even these are taken away from me? Now all I am left with are my thoughts. Cogito ergo sum said Rene Descartes. What if I am rendered thoughtless for a while by an electric shock (which I can't feel)? Would I know I existed? Not as a thought obviously but as a sense?