Why you should believe John (04 Apr 2007)
I said a couple of weeks ago that I'd write up one of the contradictions which believing in Egan-esk consciousness. (Just to recap, that means that you don't think there is anything magic about physical brains which precludes them running, in simulation, on a computer. Thus you're happy with uploads and all that other good stuff.)
Let me be running a discrete time simulation of your brain on a computer. At some time t you are in state s. I simulate you by running an update function which maps s to s+1, based on some input (vision etc) and produces some side channel outputs (your movement etc).
Now, it's a computer. I can simulate two people and each will run at half the speed. It doesn't matter that the process which is simulating your brain gets time sliced out for a few hundred milliseconds - it doesn't affect the computation at all.
So, in the middle of calculating s+1 I can go off and do other work so long as I get there in the end. It appears to you that the rest of the world is speeding up (because you are slowing down).
So I can just treat your state vector as a huge number and increment it with overflow. There is a lot of other computation which will occur before we hit s+1, but we will hit it. If we keep going we will reach s+2 and so on.
However, every single being with a state vector less than, or equal, to yours in length will live every possible life while we do it.
That's certainly a little odd.