The felt or phenomenal qualities associated with experiences, such as the feeling of a pain, or the hearing of a sound, or the viewing of a colour. To know what it is like to have an experience is to know its qualia. The idea that we first of all know qualia, and only indirectly and by their means know the properties of external things, is attacked in Wittgenstein’s private language argument, but qualia are often felt to be the major stumbling-block in front of scientific philosophies of mind, such as functionalism and physicalism. Defenders of those philosophies point out that if qualia are something over and above the physical and functional facts about an organism, they take on a character that makes them unknowable, not just from one creature to another, but even within one consciousness, at least once they have vanished into the past. Eliminativists (‘qualiaphobes’) believe that the ways of thinking that make qualia seem both so important and so elusive are wholly erroneous. See also privacy, privileged access.