An eternal light is described in Exodus in the course of setting up a mobile sanctuary while traveling though the wilderness.
This is a metaphor for our physical minds and bodies going through this world in this lifetime with a ner tamid, an eternal light within us at all times.
Last night looking up at the night sky I saw that a north wind was moving dark clouds shaped like a flock of great dark geese slowly passing overhead from north to south. And there too and was a young new moon shining between the moving clouds. Even when they seemed almost to cover her, you could always see her glow on their outer edges, and soon she was right out there clear again filled with gold light.
That eternal light, the ner tamid, is in us each all the time. Just look and you can see her light.
The Zohar (Book of Splendor) says that the great light comes out of the darkness. There can be no light without the darkness to reveal her.
