What happens when Mary leaves her black-and-white room and has a red colour experience for the first time? Here’s the answer, in outline. (I’ll assume for the sake of argument that Mary has developed the neural circuitry required for colour vision.)
- Mary’s visual system begins tracking something red, generating a huge set of active, interconnected first-order informational states, which in turn generate a vast range of reactions and reactive dispositions. Call complex of first-order informational and reactive states R1.
Mary’s introspective system begins tracking the states in R1, generating a huge set of active, interconnected second-order informational states, which in turn generate a vast range of reactions and reactive dispositions. Call this complex of higher-order informational and reactive states R2.
Mary has never instantiated R1 and R2 before and there was no practicable way to induce them in her pre-release.
The informational states in R1 and R2 carry a mass of information about the world and about Mary’s current state.
None of this information is about anything essentially private and non-physical (in the structure/dynamics sense). The informational states involved were generated by tracking physical features which could also be tracked by suitable scientific instruments and which were fully described in Mary’s textbooks.
Mary’s total informational situation is novel. She has not previously instantiated this combination of active, interconnected informational states, and there was no practicable way she could have done so pre-release.
That’s it. (5) preserves physicalism, while (6) accounts for the intuition that Mary enters a new knowledge state. Fill in the details with your preferred theories of perception, introspection, and so on.
There’s no more to say ;)