Knowledge argument

In philosophy of mind, the knowledge argument (also known as Mary's Room, Mary the Colour Scientist, or Mary the super-scientist) is a thought experiment proposed by Frank Jackson in his article "Epiphenomenal Qualia" (1982), and extended in "What Mary Didn't Know" (1986).

The thought experiment describes Mary, a scientist who exists in a black-and-white world where she has extensive access to physical descriptions of color, but no actual perceptual experience of color. Mary has learned everything there is to learn about color, but she has never actually experienced it for herself. The central question of the thought experiment is whether Mary will gain new knowledge when she goes outside the colorless world and experiences seeing in color.

The thought experiment is intended to argue against physicalism—the view that the universe, including all that is mental, is entirely physical. Jackson says that the "irresistible conclusion" is that "there are more properties than physicalists talk about". Jackson would eventually call himself a physicalist and say, in 2023, "I no longer accept the argument" though he feels that the argument should be "addressed really seriously if you are a physicalist".

The debate that emerged following its publication became the subject of an edited volume, There's Something About Mary (2004), which includes replies from such philosophers as Daniel Dennett, David Lewis, and Paul Churchland.

Thought experiment

Mary is the second character put forward by Jackson in his article Epiphenomenal Qualia. The other is a gifted person called "Fred" who "has better colour vision than anyone else on record"; Specifically, Fred can see two different colours of red where ordinary colour vision only sees one.