The ancient mystery of the "sun at midnight," symbolizes the spiritual light that lies hidden within the dark. The Celts knew that light emerges out of darkness and so their days began at dusk, as if the sun was seeded in the black earth of night.
You must not think of the light of the sun as the true Light of God. It is a reflection of the true Light. That other Light, that we can neither know nor comprehend, is so subtle, so highly potent that, for us . . . it is darkness.