Sleep is such a disparate fragment of man's life that the dismissal of its silent offering of fact as unimportant is an act of emotional prejudice and one harmful to intellectual honesty. This partial view of life is not enough. The man who confines his views of existence only within the limits of its waking field is really a narrow specialist whose conclusions cannot be trusted beyond their empirical boundaries. Nay, his conclusions are positively dangerous because within such boundaries they may be indubitably correct. He has separated a fragment of universal existence--most important, doubtless, but nevertheless a fragment--yet expects to discover the whole truth of that existence from such incomplete data. He has come to believe that his knowledge of the waking world suffices to cover the other two worlds. The instant this belief arises he falls into the trap of imagining that he understands the others when in fact he does not understand them. This delusion is dangerous also because it prevents further enquiry, hinders his advancement, and ultimately renders his mind incapable of apprehending truth.
-- Notebooks Category 19: The Reign of Relativity > Chapter 3 : The States of Consciousness > # 35
