I don't think there's any assumption, and later on he explores your point of view as well: > The matter was not nearly as strange or metaphysical as I had been

I don't think there's any assumption, and later on he explores your point of view as well: > The matter was not nearly as strange or metaphysical as I had been supposing. Where was I? In two places, clearly: both inside the vat and outside it. Just as one can stand with one foot in Connecticut and the other in Rhode Island, I was in two places at once. But this also has problems that he gets into. If the brain and body are both "you", and one is destroyed, do you not exist anymore? Do you half exist? What if your brain gets a new body or your body gets a new brain, or both at the same time? I thought the whole point of this story was to challenge the assumption that your brain and body are both "you" by imagining different scenarios that make that difficult to believe, not to just assume it isn't true. I also didn't think it made any arguments or conclusions, it's just following an interesting thread and seeing where it leads. It's supposed to be thought-provoking, not persuasive.