Let us suppose that Dave Chalmers is right about consciousness. If he is then what it is like for me to see red will turn out to be a nonphysical property of my brain. As discussed on the last post Dave thinks that phenomenal consciousness correlates with awareness (which is basically accessibility for him). So where P is the complete physical description of some person, say me, and A is a specification of my being aware of, or having access to, some mental state we will have a conditional of the form (P –> A ) that could, I suppose, be known a priori (in principle). But of course Dave thinks that zombies could have A and lack qualitative consciousness. That is why we need something like the principle of structural coherence to connect facts about awareness with qualitative facts. This gives us the conditional (A –> Q) where Q are the usual qualitative facts. These two conditionals collapse to give us (P –> Q). So for the dualist we can in principle deduce qualitative facts from the physical facts via a theory of consciousness (i.e. via the fundamental principles) a priori. But if (P –> Q) is a priori then physicalism is true. One might object that (P –> A) is knowable a priori but (A –> Q) is not since we need to introspect in order to acquire the concepts in Q. But as long as introspection only provides the concepts and does not play a role in the justification of the deduction it is still (in principle) a priori. So Dave isn’t right about consciousness.