Qualia and the Knowledge Argument: Mary's Room

Frank Jackson introduced the most influential thought experiment in the qualia debate in his 1982 paper "Epiphenomenal Qualia" (Philosophical Quarterly, vol. 32). Mary is a brilliant scientist who has spent her entire life confined to a black-and-white room, acquiring, through monochrome textbooks and a black-and-white television monitor, complete physical knowledge of the science of color vision: every physical fact about wavelengths of light, the retina's cone cells, and the neurophysiological processes of the visual cortex. When Mary is finally released and sees a ripe red tomato for the first time, Jackson argues, she learns something new — what it is like to see red — even though, by hypothesis, she already possessed every physical fact there was to know. If she learns a new fact upon leaving the room, then that fact about phenomenal experience cannot itself be a physical fact, and physicalism, the thesis that all facts are physical facts, must therefore be false.