Chandogya Upanishad is associated with the Kauthuma Shakha of the Sama Veda. It is part of the Chandogya Brahmana, which has ten chapters. The Chhaudogya Upanishad comprises of eight chapters, and commences on the Om Mantra. Chandogya Upanishad is the part of Chandogya Brahaman that contains ten chapters. The 8th Khanda of Chapter Six of Chandogya Upanishad states about sleep, hunger, thirst and death. Uddalaka, the son of Aruna told his son Svetaketu about true nature of sleep. He explained that when a person enters into deep sleep, as it said that he becomes united with Pure Being (Sat). He then goes to his own Self. Therefore, he is said to be swapiti (sleeping) as he attains his self. He then explains him with an example. Just as a bird tied by a string to the hand of the bird catcher tries to fly in different directions and then finding no place of rest, at last settles on the spot to which it is tied, the mind also after roaming towards all sides and failing to obtain a resting place, at last takes the shelter of the Soul (prana). Verily, the mind has the Soul of its tie rope. He then explains about hunger and thirst. When a man is hungry it is water that carries down the food through his gullet. Those who lead cattle are called gonaya, those who lead horses are called aswanaya, those who lead men are purushanaya; accordingly water which leads down food is called asanaya. Therefore, it is a product that has been produced from a cause. Svetaketu then enquired about its cause. His father explained that the water is he cause of the product aliment. Again, heat is the cause of the product water; and of that product heat, truth is the cause. Thus, all the different objects of the universe have the truth as their origin.
Uddalaka next explains about thirst. When a man is thirsty, the heat that carries down the drink through his gullet. Those who lead cattle are called ganaya, those who lead horses are called aswanaya, those who lead men are called purushanaya; and accordingly heat is called udanaya, the carrier of water. Therefore, it is a product that has been produced from a cause. Svetaketu then enquired about its cause. His father explained that the water is the cause, heat is the cause of the product water, and of that heat the Truth is the cause. All these varied objects of the universe have the Truth as their origin, sustenance and end. Thus, in these ways each object becomes threefold in man. When man departs his speech merges into the mind; the mind merges into life; the life into heat, and the heat into the Supreme Deity or the Highest Being. The universe has the Supreme Deity as its life. That Deity is the ultimate truth. He is the Universal Soul.
