Because value is defined in terms of the primary system, the shadow may appear as repulsive, degenerate, wrong, frightening, evil, etc. If and when the shadow becomes primary, this value system will be reversed, the world turned upside down. What was evil will be appreciated as good, and vice-versa. Shadows are cast by localized sources of light. It is not only the solidity of objects of thought, but the localization of illuminating attention, that produces contrast.
Thought always comes from somewhere.
Awareness is always identified with a perspective, with the premises of some system, beginning with the body, and focussed on some object. Such thought cannot contain opposites, cannot encompass both the object and its shadow in the same breath. It cannot illuminate areas hiding in shade. Even so, there are no intrinsically dark regions. Darkness is always relative to the source of light, to the mind's assumptions.