Functionalism offers an account of the relations that hold between behavioural functions, information and neural processing, and conscious experience from which one can draw two inferences: for any discriminable difference between qualia there must be an equivalent discriminable difference in function; and for any discriminable functional difference within a behavioural domain associated with qualia, there must be a discriminable difference between qualia. The phenomenon of coloured hearing synaesthesia appears to contradict the second of these inferences. We report data showing that (...) this form of synaesthesia is genuine and probably results from an aberrant projection from cortical language areas to a region specialized for the perception of colour. Since functionalism purports to be a general account of consciousness, one such negative instance, if it can be further sustained empirically, is sufficient to invalidate it. (shrink)