The impossibility of an "uploaded mind" relies on the assumption that there is something special about the mechanisms behind the human brain's function that cannot be replicated in a machine (including an artificial, organic computer). The brain's function would have to the the result of something other than the structure and organisation of its biology.
(Probably the people who believe in the possibility of minds in machines would argue 'souls' and 'personality' are also purely functions of the underlying biology and learning, and thus could also be made artificially).
"Consciousness" itself is tricky to define, as it is essentially defined only by the experience of the evaluator. We are little further in our understanding then Descarte's, "I think, therefore I am". Our evaluation of the consciousness of other entities is limited to traits in them that we see in ourselves. "It thinks like me, therefore it is, too." Hence the appeal of the Turing's Imitation Game to evaluate artificial intelligence.
(Probably the people who believe in the possibility of minds in machines would argue 'souls' and 'personality' are also purely functions of the underlying biology and learning, and thus could also be made artificially).
"Consciousness" itself is tricky to define, as it is essentially defined only by the experience of the evaluator. We are little further in our understanding then Descarte's, "I think, therefore I am". Our evaluation of the consciousness of other entities is limited to traits in them that we see in ourselves. "It thinks like me, therefore it is, too." Hence the appeal of the Turing's Imitation Game to evaluate artificial intelligence.