He sees life as naturalistic dualism. In terms of consciousness, this means, physical explanations of mental experiences don’t hit the target. Mental states can be caused by physical systems such as our brains but mental states, such as altered states of consciousness, cannot be described in terms of physical systems.
How non-conscious sensory stimuli becomes conscious experience is not known. We try to connect the two through the use of language. But language can only hint at non-verbal states. As crude a tool as language is, it is all we have to at least try to communicate what these varying states of awareness feel like.