The first, as I think Yudkowsky states, is that qualia are not very well defined. Human introspection is unreliable in many cases, and we're only consciously aware of a subset of processes in our brains. This means that the fact that zombies are conceivable doesn't mean they are logically possible. When we examine what consciousness entails in terms of attention to mental processes, zombies might be logically impossible.
Second, one of the false intuitions humans have about consciousness goes something like this:
"If I draw up a schematic or simulation ...
Yes, great conversation. Great meeting everyone.
I think I'm saying more than this. We might find that it is impossible for beings like ourselves to not have qualia. By analogy, consider the Goldbach conjecture. It's possibly try but not provable with a finite proof. But it's also possibly false, and possibly provably so with a finite proof. It's conceivable that the Goldbach conjecture is true, and conceivable that it is false, but only one of the two cases is log... (read more)