William James (1902)

Our normal waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it, parted from it by the filmiest of screens, there lie potential forms of consciousness entirely different. We may go through life without suspecting their existence; but apply the requisite stimulus, and at a touch they are there in all their completeness ... No account of the universe in its totality can be final which leaves these other forms of consciousness quite disregarded. How to regard them is the question ...