PEOPLE who think solely on the basis of nature cannot grasp the fact that there is light in the heavens; yet in the heavens there is so much light that it is vastly greater than noonday light on earth. I have seen it often, even during our evenings and nights. At first I was amazed when I heard angels saying that our world’s light was nothing but shadow in comparison to heaven’s light, but now that I have seen it, I myself can bear witness. Its brightness and brilliance are beyond description. What I have seen in heaven I have seen in that light, and therefore more clearly and distinctly than what I have seen in this world.
Heaven’s light is not natural like the light of our world, but spiritual. It actually comes from the Lord as the sun, and that sun, as explained in the preceding chapter, is divine love. While what emanates from the Lord as the sun is called divine truth in the heavens, in essence it is divine good as one with divine truth. This is the source of light and warmth for angels: they get their light from the divine truth and their warmth from the divine good.
We can therefore conclude that heaven’s light, in view of the nature of its source, is spiritual and not natural, as is its warmth.
from Heaven and Hell, Sections 126, 127