Qualia

Qualia, or the singular quale, are defined to be the subjective and experiential moments of consciousness. That is, they are your subjective perceptions (though qualia can be inner as well) that are considered to be achieved through introspection/reflection. So, when you see the color red, there is the objective fact of wavelengths, color spectrums, etc. but you also have a subjective experience of the color red. It is essentially private, and based on you. The problem of admitting the existence of qualia is that it poses a problem for many reductive materialists, or physicalists in general, sense such mental states [qualia] do not seem reducing to physical processes. The thought experiment usually used to intuit this is by way of Mary's Room. In this experiment, Mary has lived inside a black-and-white room for her entire life. But, she does have all the books and learning materials possible relating to color theory. So, she knows all there is to know about what colors (with the textbooks having no visual representation) are presented with certain wavelengths, and how they reflect on an object, how the light is absorbed, etc. The question is: if Mary were to suddenly walk out from the room and into a colorful world, would she gain any new knowledge about what colors look like? Does she gain anything by that experience? Some deny so, but most say that yes, Mary does seem to gain some sort of knowledge about colors that she can't get from merely knowing the physical processes of light, the eyes, and the brain. Thus, it seems like we must admit the existence of qualia.