The yin and yang represent all the opposite principles one finds in the universe. Under yang are the principles of maleness, the sun, creation, heat, light, Heaven, dominance, and so on, and under yin are the principles of femaleness, the moon, completion, cold, darkness, material forms, submission, and so on. Each of these opposites produce the other: Heaven creates the ideas of things under yang, the earth produces their material forms under yin, and vice versa; creation occurs under the principle of yang, the completion of the created thing occurs under yin, and vice versa, and so on. This production of yin from yang and yang from yin occurs cyclically and constantly, so that no one principle continually dominates the other or determines the other. All opposites that one experiences—health and sickness, wealth and poverty, power and submission—can be explained in reference to the temporary dominance of one principle over the other. Since no one principle dominates eternally, that means that all conditions are subject to change into their opposites.

This cyclical nature of yin and yang, the opposing forces of change in the universe, mean several things. First, that all phenomena change into their opposites in an eternal cycle of reversal. Second, since the one principle produces the other, all phenomena have within them the seeds of their opposite state, that is, sickness has the seeds of health, health contains the seeds of sickness, wealth contains the seeds of poverty, etc. Third, even though an opposite may not be seen to be present, since one principle produces the other, no phenomenon is completely devoid of its opposite state. One is never really healthy since health contains the principle of its opposite, sickness. This is called "presence in absence." Once you have this principle down, the particular Chinese view as expressed in literature.

In Oriental art, medicine and philosophy, everything is classified under these two stems. To maintain harmony and order in the universe and within the body, is to keep the Yin and Yang constantly in delicate balance. Chaos and disharmony abound when their even pull is disturbed in any way. Like opposite poles of a magnet, the Yin will attract a Yang, but will repel another Yin force.

For the purpose of Chinese horoscope reading, it should be noted that the Yin and Yang only repels the similar negative or positive stem directly opposite its polarity. If you refer to the incompatibility circle, you will see that all the conflicting signs belong to the same stem. Only if the animal signs are directly across from each other is there any repelling action. In the triangles of affinity you can see how three positive or negative signs can be harmonious when they are 120 degrees away from one another.

Applying the Yin and Yang principle to the five elements in the horoscope may be a more complicated matter. For instance, the positive stem of Wood is a fir tree, the negative is the flexible bamboo. The positive stem of Fire may be a forest fire, the negative could be a lamp or candle that emits beneficial light. The positive of the Earth element, a hill; the negative, a valley. The positive of Metal, a gong or weapon; the negative, a cooking pot or coin. The positive stem of Water, a wave; the negative, still water.

The "negative" here should not be taken in a pejorative sense as it does not mean something bad or undesirable in this context. Both the positive (Yang) and negative (Yin) forces have their good and bad aspects. For instance, a person born under a positive sign will find himself more effective when he proceeds in active ways. It would be "negative" (in the pejorative sense) for him to proceed in a passive way. Similarly, a person born under a negative sign is at his best when he behaves in a passive or nonaggressive manner. The first is compelled to be a doer and innovator, the second excels as a thinker and negotiator. Generally, Yang people are more spontaneous, Yin people more reflective and intuitive.

In the Chinese system of casting fortunes, the Yin and Yang will appear alternately with the same element in combination with the twelve animal signs. Thus, the Yang (+) will be paired off with the Fire element first in, let us say, the year of the mouse (1936). Immediately following, in the year of the Ox (1937), the Yin (-) force will have its turn to be combined with the same element, Fire, to balance off the Yang force.

We therefore find that there will be only six changes of elements in a normal twelve-year cycle, because each element must appear twice, once in its positive state and once in its negative state.