THEORIES OF LEARNING: Page 42

thing about everything—and there is so much to know. There just isn't enough time during waking hours. Often we are too tired to even care about improving ourselves. Yes, sleep-learning has much modern appeal. Still, only by knowing how we learn can we examine the effectiveness of sleep-learning. There is not, of course, complete agreement among authorities but if we can unearth points on which they do agree then we can evaluate sleep-learning against accepted theories. Looking back a few centuries (1690), we find John Locke challenging the old doctrine that men come into the world with a set of ideas and a particular character stamped on their minds. He argued that knowledge was derived from experience, the result of ideas acquired through the five senses, and from inner experiences of the mind which operate in considering the ideas derived from sensations. Only what can be perceived exists, according to George Berkeley (1710), and various combinations of perceptions come to signify objects or ideas. The perceiving is done by a distinct entity, the self, and nothing can exist except in the mind which perceives it. Berkeley asserted that all reality was mental and all nature a manifestation of God. David Hume later (1748) affirmed that there was no knowledge beyond the evidence of the senses, that there was no such thing as cause and effect and that experience was primary in all thinking. He divided the mind's perceptions into impressions (sensations, passions, emotions ) and ideas by which he meant the faint images of impressions in thinking and reasoning.