Esoteric Astrology

To everything existing there are two sides, the spiritual and the material, the essential and the formal. We are living in a world of duality through which something subtle and undefinable is continually passing and flowing, as an essence or principle behind all things that have this dual manifestation. This may be fittingly illustrated by the contrast of Day and Night, sub-divided again by Sunrise and Sunset, Noon and Midnight, when the conditions of the earth are completely changed and reversed.
The only external factor here is the rotation of the earth upon her own axis before the face of the Sun. But what is it that causes the rotation, and the changing influence of Sunrise and Sunset ?