More about this: it’s easy but non trivial to start relaxing the assumptions that 1) our physics simulation is complete and accurate down to the lowest level and 2) we simulate all of physics rather than just the conscious system in question.

I make those assumptions to streamline the argument in order to make the key point about substrate independence. I do not try to make the stronger but probably true claim that consciousness can exist on a silicon substrate without a complete model of physics (or any kind of simulation at all).