The symbolism of astronomy lends itself in a most interesting manner to the great problem of human evolution. In my opening chapter it was shown that evolution is the natural reaction to the process of involution. Logically we cannot speak of evolution without taking into consideration the fact of a preceding involution. _Ex nihilo nihil fit._ The potential of matter is measured by its latent energy, and this latency is static Spirit Force. Matter is the ultimate expression of Spirit, as form is that of force. The material forms of the visible universe are therefore nothing but concrete spiritual forces. But it would appear that there are two processes going on simultaneously in any cycle of cosmic life, and these are a downward spiritual involution and an upward physical evolution. The two processes are complementary, and possibly may be regarded as taking place simultaneously, although in the Chaldean account they are spoken of as distinct in point of time. Jacob’s vision of the Ladder of Life depicted angels ascending and descending simultaneously, and these are the spiritual forces that are in continual play between pure spirit and gross matter. The great tidal influx of spirit towards the plane of materiality admits of a constant ebb and flow of the life-wave, so that, although at the present stage of the Great Cycle the tide has set back and is at its ebb, carrying its burden of detached souls along with it towards the region of spirituality, may yet mark periodic incursions of the spirit towards the material plane, such incursions being in the nature of abnormal phenomena. Thus we have from the beginning of the Great Cycle a double influx involving an interplay of Spirit and Matter. In the process of manifestation by means of differentiation, Spirit (the positive or male potency) may be regarded as taking a downward plunge on the left-hand side, while Substance (the negative or female potency) will in the same scheme take the right-hand side in its progress towards manifestation on the material plane. The Paramatma or Universal Spirit first appears as Purusha, while Mulaprakriti or Root Substance manifests as Prakriti. The ultimate expression of Purusha is Prana (Life force) while that of Prakriti is Prithivi (Matter). We thus have the Father Spirit on the one hand, and the Mother Substance on the other, manifesting eventually in the multitude of forms of Living Matter. Spirit Substance thus invests and is at the root of all physical life, Force and Matter standing always in the same undivided relations as do Spirit and Substance in the Archetypal World.