Chalmers is best known for his formulation of the notion of a hard problem of consciousness in both his 1996 book and in the 1995 paper “Facing Up to the Problem of Consciousness”. He makes a distinction between “easy” problems of consciousness, such as explaining object discrimination or verbal reports, and the single hard problem, which could be stated “why does the feeling which accompanies awareness of sensory information exist at all?” The essential difference between the (cognitive) easy problems and

Source: David Chalmers – Wikipedia, the free encyclopedia