17. ‘That’ means Brahman, that which is far away, unknown. Brahman is the substratum of the universe. The universes come and go. Brahman remains. ‘This’ is Atman, that which is closest to you, the most intimate part of you. Brahman and Atman are one, inseparable entity.
When you dream the entire dream world seems very real to you. Yet when you wake up you understand it was a mere fancy, a projection of the mind. Nothing that happens in the dream world can impact on the waking state. A devastating fire in the dream cannot change the calm demeanour of the waker’s mind.
Arjuna is disturbed about death. Krsna appeases him by saying the real You never dies. You are the imperishable substratum of the universe. The waking, dream and deep sleep worlds are born out of Brahman, exist in Brahman and dissolve back into Brahman. They are perishable. Brahman is imperishable. You are imperishable. Nobody can destroy you.
Yet you are crushed, affected, disturbed by the world because of ignorance. You do not know your strength. You do not know yourself. Wake up to your real identity. Understand your own power. Nothing in the world will disturb you.
Arjuna is too agitated to understand this yet the powerful assertion of the truth from an enlightened Soul calms Arjuna.
18. Then what is it that perishes at death? The bodies are born and they die. Atman does not die when the bodies die. The sun above is imperishable. Its reflections in mirrors die. When a mirror breaks you do not mourn the death of the sun! You just replace the mirror. So identify with Atman. You will be free from the traumatic changes in the body. Rise above the world and you will become the eternal, all-pervading, indestructible Being.
The Indweller, Atman, is eternal, immeasurable and indestructible. The world is a function of time, space and causation. Time extends indefinitely into the past and future. It is eternal. There is no end to space. Causation also goes on. The world seems to reflect these three attributes of Brahman. They make the essence of the world. Just as the properties of the rope exist in the illusory snake you project.