A scientist who knows every fact about colour learns something new the moment she sees it

Philosopher Frank Jackson imagined Mary, a brilliant scientist who has spent her whole life in a black-and-white room but knows every physical fact there is about colour vision. The moment she steps outside and sees red for the first time, does she learn something new? If so, Jackson argued, physical facts can't be the whole story of conscious experience.

— Frank Jackson, Epiphenomenal Qualia — The Philosophical Quarterly, 1982