Mary’s room is a philosophical thought experiment used to question a physical or materialistic explanation of consciousness and mind. The argument has various forms but it essentially boils down to a situation where Mary is a scientist who cannot see colours but goes about to study everything physical there is to know about colour. So she learns about light, quantum mechanics, molecular biology, photoreceptors, neuroscience, psychology, art, and so forth. Then suddenly her colour vision is restored. The question then is whether or not she has learned something new. If you answer yes, then there cannot possibly be a physical or material explanation of consciousness since she has learned everything that she could about the physical properties of colour vision. The thought experiment is meant to highlight that there seems to be something special and nonphysical about qualia.
I’m certain that most everyone has at one point wondered if what they call red looks the same to someone else. How many times have you had a conversation where someone says “How do I know that my red is not your blue?” The philosopher David Chalmers uses Mary’s room as one of his arguments against a pure physical explanation of consciousness. I believe he is the person who coined the term “the hard problem of consciousness”, for the issue of how to understand the awareness of consciousness. His arguments are quite compelling but I haven’t quite jumped off the materialistic bandwagon. My response to Mary’s room is that if Mary truly discovered everything to know about consciousness then she will not learn anything new when her colour vision is restored. However, I might differ from other materialists in that I believe that she would have to simulate colour vision in her brain to qualify as knowing everything physical because there is a profound difference between knowing what an algorithm is and actually executing it. The reason, which drives much of my recent philosophical inquiry, is the Halting Problem.