Let me try something here, because I am still wrestling with this issue.
Would it be accurate then, to model our consciousness like a very complex finite state machine with some very large number of possible states? As our consciousness cycles through the various states, driven by sensory input, two separate consciousnesses may fleetingly produce similar/identical states given identical sensory inputs? The paths leading to the momentary near-same states can be different as well as the paths leading out of the state (hence the inability to know what it is like to be someone else, even if you fleetingly produce a similar state), but for a moment you would be very similar to the other individual.
Of course, this could also explain how people receiving very different sensory inputs could arrive at similar states (e.g. pleasure=pleasure vs. pain=pleasure).
It seems to me that equivalent states don't equal equivalent consciousness; rather equivalent operators/variables from which the state is produced would have to be identical (as would all subsequent inputs to keep the variables synchronized). That is, it is only possible for two different consciousnesses to be near-identical for a very small moment, but it is possible.
Hmm... It seems that I've made consciousness look like a really complex stream function (like an RC4 PRNG).
-James Rogers
jamesr@best.com