The Upanishads are called shruti revelations. Mandukya Upanishad though the shortest of all Upanishads is a revered profound Upanishad that teaches us about four states of consciousness: the waking dreaming and sleeping states and Turiya the fourth state beyond the first three. In this Upanishad there is a unique combination of psychology and profound philosophy a clear exposition of the four states of consciousness.
