That multiplicity[16] may be manifest, differences must be produced in Unity; these differences in the world are the "pairs of opposites"--the contraries. These contraries are everywhere. Matter is the fulcrum of force--both of these terms being "aspects" of God--and without a fulcrum no force can manifest itself; there is no heat without cold, and when it is summer in the northern hemisphere it is winter in the southern. There is no movement that does not depend upon a state of rest, no light without shadow, no pleasure without the faculty of pain, no freedom that is not founded upon necessity, no good that does not betoken an evil. The following are a few examples of duality taken from nature. The current of electricity is polarised into a positive and a negative current. It is the same with the magnet; though you break a bar into a hundred pieces, you bring into being a hundred small magnets, each possessing its positive and negative side; you will not have destroyed the "duality," the opposites. Like the magnet, the solar spectrum forms two series, separated by a neutral point, the blue series and the red one, united by the violet.[17] Violet. Indigo. Yellow. Blue. Orange. Green. Red. The terms of the two series are respectively complimentary to each other; the violet dominates the two groups of opposites and is a visible member of the axis formed by the colours that might be called neutral. Duality appears in every shape and form. Symbolically, we may say with the Hindus that the Universe begins and ends with two opposite movements: an emanation from Brahma, it is born when the breast of God sends forth the heavenly outbreathing, it dies, reabsorbed, when the universal inbreathing takes place. These movements produce attraction and repulsion, the aggregation and dissolution to be found everywhere. It is the attraction of a force-centre, the "laya centre" of Theosophy, which permits of the atomic condensation that gives it the envelope whose soul it is; when its cycle of activity ends, attraction gives place to repulsion, the envelope is destroyed by the return of its constituent elements to the source from which they were drawn, and the soul is liberated until a future cycle of activity begins. Even the rhythm of pulmonary respiration, the contraction and dilation (systole and diastole) of the heart, the ebb and flow of the tides, as also day and night, sleeping and waking, summer and winter, life and death, are all products of that law of contraries which rules creation.