From the Kabbalah (Cabala):
Polarity is the principle that runs through the whole of creation,and is in fact, the basis of manifestation. Polarity really means the flowing of force from a sphere of high pressure to a sphere of low pressure, high and low being always relative terms. Every sphere of energy needs to receive the stimulus of an influx of energy at higher pressure, and to have an output into a sphere of lower pressure. The source of all energy is the Great Unmanifest (God), and it makes its own way down the levels, changing its form from one to the other, till it is finally "earthed" in matter.