Qualia include the ways things look, sound and smell, the way it feels to have a pain, and more generally, what it's like to have experiential mental states. (‘Qualia’ is the plural of ‘quale’.) Qualia are experiential properties of sensations, feelings, perceptions and, more controversially, thoughts and desires as well. But, so defined, who could deny that qualia exist? Although the existence of subjective experience is not (or anyway should not be) controversial, ‘quale’—which is more clearly a technical term than ‘subjective experience’ is more often used by those who are inclined to reject the common-sense conception of subjective experience. Here is a first approximation to a statement of what is controversial: whether the phenomenology of experience can be exhaustively analyzed in intentional, functional or purely cognitive terms.Feelings and experiences vary widely. For example, I run my fingers over sandpaper, smell a skunk, feel a sharp pain in my finger, seem to see bright purple, become extremely angry. In each of these cases, I am the subject of a mental state with a very distinctive subjective character. There is something it is like for me to undergo each state, some phenomenology that it has. Philosophers often use the term ‘qualia’ (singular ‘quale’) to refer to the introspectively accessible, phenomenal aspects of our mental lives. In this standard, broad sense of the term, it is difficult to deny that there are qualia. Disagreement typically centers on which mental states have qualia, whether qualia are intrinsic qualities of their bearers, and how qualia relate to the physical world both inside and outside the head. The status of qualia is hotly debated in philosophy largely because it is central to a proper understanding of the nature of consciousness. Qualia are at the very heart of the mind-body problem.