Mandukya_Upanishad

CONSCIOUSNESS AND SLEEPThe waking world and the dream world, from the pointof view of the jīva, are two aspects of the function of themind. The mind projects itself in perception, both inwaking and dream. The mind is active, and it gets tired ofactivity. It ceases from activity when it is too much fatigued.The complete cessation of the activity of the mind, due toexhaustion, is sleep, known as suṣhupti.That is called suṣhupti, or deep sleep, where – nakancana kāmam kāmayate – one desires nothing, becausethe mind has withdrawn itself from both the physical andsubtle objects. Na kancana svapnam paśyati: It does notdream also, because even psychic activity has ceased. Tatsuṣhuptam: This is complete absorption of the mind intoitself. But this absorption is of an unconscious nature.The mind, while it appears to be a little conscious indream, and more conscious in waking, is not conscious atall in deep sleep. This has given rise to an erroneous schoolof philosophy which concludes that consciousness ispossible only when there is contact of the mind withobjects. The nyāya and the vaiśeshika hold this view. Unlessthere is contact of the Ātman, they say, with objects, therecannot be knowledge. The real nature of the Ātman, while itis not in contact with things, is not knowledge, say thenyāya and the vaiśeshika. They are not right because theycannot explain how this unconscious element creeps intothe state of sleep. The reason is not merely thatconsciousness has no contact with objects but that it hassome other obstruction to the revelation of knowledge indeep sleep.