“If the eye that adventures the vision be dimmed by vice, impure, or weak, and unable in its cowardly blenching to see the uttermost brightness, then it sees nothing even though another point to what lies plain to sight before it. To any vision must be brought an eye adapted to what is to be seen, and having some likeness to it. Never did eye see the sun unless it had first become sunlike, and never can the soul have vision of the First Beauty unless itself be beautiful.”

Plotinus: On Beauty 1.6.9.