  While physicalism requires only that a conscious state depends entirely on an
underlying physical state, it is often assumed that consciousness is
algorithmic and that conscious states can be copied, such as by copying or
digitizing the human brain. In an effort to further elucidate the physical
nature of consciousness, I challenge these assumptions and attempt to prove the
Single Stream of Consciousness Theorem (SSCT): that a conscious entity cannot
experience more than one stream of consciousness from a given conscious state.
Assuming only that consciousness is a purely physical phenomenon, it is shown
that both Special Relativity and Multiverse theory independently imply SSCT and
that the Many Worlds Interpretation of quantum mechanics is inadequate to
counter it. Then, SSCT is shown to be incompatible with Strong Artificial
Intelligence, implying that consciousness cannot be created or simulated by a
computer. Finally, SSCT is shown to imply that a conscious state cannot be
physically reset to an earlier conscious state nor can it be duplicated by any
physical means. The profound but counterintuitive implications of these
conclusions are briefly discussed.
