Brihadaaranyaka Upanishad has a wonderful explanation about "self" the fifth and ultimate source of light available for human beings. A self realized soul, a great sage, came to King Janaka's court. King Janaka requested the sage to talk about the light of lights that lights a man's way in the world. Sage said: There are five lights: Sun lights a man's way during the day, Moon at night, Fire lights his way when there is neither the sun nor the moon and Voice can help to some extend to know a man's way. ( When it is dark, sounds can help us move to that place from which the sound came). But when it is pitch dark, and all sounds have stopped, "Self" or the "knowing one" or "inner light" is the light that lights a man's way. Then he continued the explanation of this "seer" or "master of all" or the "ultimate controller" of everything. It is this "self" who sees us ...