Mary the colour scientist

Mary is a neuroscientist who is, for whatever reason, forced to investigate the world from a black and white room via black and white technology. She specialises in the neuroscience of visual systems and has acquired, let us suppose, all the information that there is to acquire on the material, physical bases of colour vision. She knows what happens when a person sees ripe tomatoes or the sky and she can use terms like ‘red’ and ‘blue’ to describe accurately what a person sees when she is looking at a ripe tomato or at the sky. She discovers, for example, just which wave-length combinations from the sky stimulate the retina and exactly how this produces, via the central nervous system, the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue.’ She has discovered just what happens when light hits the retina and how the visual system is activated and how a particular area of the visual brain is responsible for colour vision. So, Mary is an expert colour scientist. From her black and white room she has come to know everything there is to know about the physical bases of colour visual consciousness.