What does a man work into his astral body? What we call goodness and common sense. If you observe a savage who is still on the level of a cannibal, blindly following his passions, you must say of him that he stands lower than the animals because the animal still has no understanding, no consciousness of his deeds. Man, however, even the lowest, already has an ego. The more highly educated person can be distinguished from the savage through the fact that he has already worked on his astral body. Certain passions he has so understood that he says to himself, “This one I may follow, this other I may not follow.” Certain urges and passions he fashions to more refined configurations, which he calls his ideal. He forms moral concepts. All these are transformations of his astral body. The savage cannot do arithmetic or make judgments. This property man has acquired through work on his astral body from incarnation to incarnation. What develops as man gradually ennobles his present imperfect form to become that being of light of whom we spoke is called the assimilation of wisdom. The more wisdom the astral body contains, the more luminous it will be. The Elohim, those beings who dwelt on the Sun, were wholly permeated with wisdom. Just as our souls relate to our bodies, so wisdom relates itself to light that streams out into cosmic space. You see, the relation between light and wisdom is not an image that has been contrived. It is based on fact. It is a truth. Thus is it to be explained that religious documents speak of light as a symbol of wisdom."
Source: Occult Signs and Symbols