The Bible pictures this as the earth being without form and void. Diversity flows out from the one reality magically and in an orderly way, the way leaves do from a branch. What is within expresses without, in the way a vague idea grows gradually more defined and gives birth to a well-formed thought or series of concepts. Or as a film negative develops slowly in its chemical bath till a clearly defined image evolves. Or as a single seed nourished by sun and moon, water and earth, progressively grows the male and female aspects it requires to reproduce itself, the feminine growing simultaneously with the masculine principle.
Diversity begins as duality.
Like the coupling of oxygen and hydrogen to make water, one isn't more or less essential than the other. But though both are essential, inseparable, and rooted in the same source, they are different. Commonly the masculine principle is said to be related to action, spirit, light, and energy. So wherever the masculine expresses itself, it can only do so through the feminine. On cosmic planes, The Secret Doctrine presents the waters of space as feminine, and the akasa, the aethers, and astral regions as all having their feminine aspects.