Light is an emanation from the sun, but the sun is itself an emanation from God. When it is full of Him, then it is full of light. So the ancient Rishis used to say that He was in the sun. /Yo’sau purusah /etc. But this was only a manner of speaking. When the sun is full of God's presence, it is full of light and heat, when it is empty of Him, the light and heat are withdrawn. So too the human soul is like the sun: When it is full of light and heat, it is said to be alive, when the light and heat are withdrawn, it is said to die. But this too is only a manner of speaking. The soul is imperishable. When the body feels the presence of God within, it is conscious of life, but when the light and heat of His presence are withdrawn it ceases to become active and conscious. This is called death. There is no hard and fast line to be drawn between life and death. The one is only the positive, the other the negative of God's presence. Chandogya Upanishad 16.19 Page 710, Bande Mataram , volume 1, SABCL