Yin and Yang

Chang Tsai, (1020-1078), philosopher:

No two of the products of creation are alike. From this we know that although the number of things is infinite, at bottom there is nothing without yin or yang [which differentiate them]. From this we know also that the transformations and changes in the universe are due to these two fundamental forces.

Material force moves and flows in all directions and in all manners. Its two elements unite and give rise to the concrete. Thus the multiplicity of things and human beings is produced. In their ceaseless successions the two elements of yin and yang constitute the great principles of the universe.

Only after [the One] is acted upon will it begin to penetrate [through yin and yang]. Without the two forces there cannot be the One.
If yin and yang do not exist, the One (the Great Ultimate)" can not revealed If the One cannot be revealed then the function of the two forces will cease, Reality and unreality, motion and rest, integration and disintegration, and clearness and turbidity are two different substances. In the final analysis, however, they are one.

The negative and positive spiritual forces (kuei-shen) are the spontaneous activity of the two material forces (yin and yang). Sage hood means absolute sincerity (1) forming a unity with Heaven, and spirit means the Great Vacuity in its wondrous operation and response. All molds and forms in the universe are but dregs of this spiritual transformation.

Shao Yong(1012-1077), philosopher:

Without physical substance, the nature (of man and things) cannot be complete. Without nature, physical substance cannot be produced. The yang has the yin as its physical substance and the yin has the yang as its nature. Nature is active but physical substance is tranquil. In heaven, yang is active while yin is tranquil, whereas in earth yang is tranquil while yin is active. When nature is given physical substance, it becomes tranquil. As physical substance follows nature, it becomes active. Hence yang is at ease with itself but yin is fast moving without control.

As the Great Ultimate becomes differentiated, the Two Modes (yin and yang) appear. Yang descends and interacts with yin, and yin rises to interact with yang, and consequently the Four Forms (major and minor yin and yang) are constituted. Yin and yang interact and generate the Four Forms of Heaven: the element of weakness and the element of strength interact and generate the Four Forms of Earth; and consequently the Eight Elements (heaven, water, fire, thunder, wind, water in motion, mountain, and earth) are completed. The Eight Elements intermingle and generate the myriad things. Therefore the one is differentiated into the two, two into four, four into eight, eight into sixteen, sixteen into thirty-two, and thirty-two into sixty-four. Thus it is said (in the Book of Changes) that "they are distinguished as yin and yang and the weak and the strong are employed in succession. Thus in the system of Change there are six positions and the pattern is complete. Ten is divided to become 100, 1,000, and 10,000. This is similar to the fact that the root engenders the trunk; the trunk, branches; and the branches, leaves. The greater the division, the smaller the result, and the finer the division, the more complex. Taken as a unit, it is one. Taken as diffused development, it is the many.