IN heaven, the divine nature that emanates from the Lord is called divine truth, for reasons that will be given below. This divine truth flows into heaven from the Lord, out of his divine love. Divine love and the divine truth that derives from it are like the sun’s fire and the light that comes from it in our world. The love is like the sun’s fire, and the derivative truth is like the light from the sun. By reason of correspondence, fire means love and light means the truth that flows from it.
This enables us to determine the character of the divine truth that emanates from divine love: in its essence, it is divine good united to divine truth, and because it is united, it gives life to everything in heaven the way the warmth of the sun, united to its light, makes everything fruitful on earth in spring and summer. It is different when the warmth is not united to light, when the light is therefore cold. Then everything slows down and lies there, snuffed out.
The divine good we have compared to warmth is the good of love within and among angels, and the divine truth we have compared to light is the means and the source of this good of love.
The reason the Divine in heaven (which in fact makes heaven) is love is that love is spiritual union. It unites angels to the Lord and unites them with each other. It does this so thoroughly that in the Lord’s sight they are like a single being. Further, love is the essential reality of every individual life. It is therefore the source of the life of angels and the life of people here. Anyone who weighs the matter will discover that love is our vital core. We grow warm because of its presence and cold because of its absence, and when it is completely gone, we die. We do need to realize, though, that it is the quality of our love that determines the quality of this life.
from Heaven and Hell, Sections 13, 14