Mary knows every physical fact about human color vision but has lived her whole life in a black-and-white room. When she steps out and sees a red tomato, does she learn something new? This episode unpacks Frank Jackson's 1982 knowledge argument and why the answer threatens physicalism, the scientific view that everything in the universe, including consciousness, is entirely physical. We define qualia, explain Jackson's original epiphenomenalist conclusion that subjective feelings are caused by the brain but cause nothing themselves, and lay out the evolutionary objection that useless feelings should never have evolved.

We connect the puzzle to C.D. Broad's 1925 archangel who cannot predict the smell of ammonia and Thomas Nagel's 1974 essay on what it is like to be a bat, then work through the physicalist counterattacks: Evan Thompson's poin ...