The further we study the phenomenon of deep sleep the more we will come to understand the mystery of life. It gives a key to the mystery of life, for it is an experience which divides our spiritual consciousness between the physical and spiritual worlds. It stands as a barrier between two experiences, one in this world, and one which is reached by spiritual attainment. The great Persian poet Rumi has written about sleep; he says, 'O sleep! It is thou who makest the king unaware of his kingdom and the suffering patient forget his illness, and prisoners are free when they are asleep.' All pains and sorrows and limitations of life, all the tragedy of life, all sufferings and agitations are washed away when one experiences that deep sleep.