We may, if we like, by our reasonings unwind things back to that black and jointless continuity of space and moving clouds of swarming atoms which science calls the only real world. But all the while the world we feel and live in will be that which our ancestors and we, by slowly cumulative strokes of choice, have extricated out of this, like sculptors, by simply removing portions of the given stuff. Other sculptors, other statues from the same stone! Other minds, other worlds from the same monotonous and inexpressive chaos! My world is but one in a million alike embedded, alike real to those who may abstract them.William James, The Principles of Psychology (1890)
In the same chapter James coined the phrase 'stream of consciousness.' Some recent research casts doubt on that — see, for example, Gregory Hickok quote here. Earlier in the same passage (quoted in a longer extract by Cosma Rohilla Shalizi) James describes the mind as 'at every state at every stage a theatre of simultaneous possibilities...'
Consciousness consists in the comparison of these with each other, the selection of some, and the suppression of the rest by the reinforcing and inhibiting agency of attention.