"The easy problems of consciousness are about explaining cognitive functions: attention, memory, learning, language. Science can do that. The hard problem is why any of it is experienced at all. Why is there something it is like to be me? That question does not have a two-body answer. It requires a third body: the coordination between physical process and subjective experience."
Philosopher at NYU who coined 'the hard problem of consciousness' in 1994, crystallizing the distinction between explaining cognitive function and explaining subjective experience. His philosophical zombies thought experiment — beings physically identical to humans but with no inner experience — shows that physical description alone does not generate phenomenology. His more recent 'Reality+' argues that virtual experiences are fully real experiences, dissolving the boundary between physical and digital worlds.