Zhang Zai (Chang Tsai, 1020-1077) was a Neo-Confucian philosopher who lived during the Sung Dynasty (960-1279). He had an important influence on later Neo-Confucian philosophers, such as the Cheng brothers: Cheng Hao (1032-85) and Cheng Yi (1033-1108). His most important work was the Zheng Meng.

Zheng Meng (Correct Discipline for Beginners) is divided into seventeen chapters. The titles of the chapters are: 1) "The Great Harmony," 2) "The Triad and Dyad," 3) "The Dao of Heaven," 4) "The Divine Character," 5) "Animals," 6) "Truth and Enlightenment," 7) "Largeness of Mind," 8) "The Golden Mean and the Right," 9) "The Highest Development," 10) "Originality," 11) "Thirty Years of Age," 12) "The Virtuous," 13) "Government," 14) "The Book of Changes," 15) "Music," 16) "The Sacrificial Ceremony to Heaven," and 17) "The Principles of Qian."¹

Two additional treatises were separated from the seventeenth chapter, and were titled "The Western Inscription" and "The Eastern Inscription"².

The most fundamental concept in Zhang Zai’s philosophy is qi (ch’i), which is material force or cosmic energy. Material force is the energy of matter, spread throughout the universe. Material force is both matter and energy. Matter and energy are not separated, they are united.

Material force is always changing. Originally, it is formless; but it may integrate and thereby gain form, or may disintegrate and thereby lose physical form. Zhang Zai says that the integration or disintegration of material force is like the freezing of water or the melting of ice (chapter 1, section 7).

Material force may have substance, or may have no substance. It may have form, or may have no physical form. The presence or absence of form may be caused by changes of material force.

The principle (li) of change may cause continuous fusion and diffusion, expansion and contraction, attraction and repulsion, floating and sinking, rising and falling, integration and disintegration.

According to Zhang Zai, material force may integrate or disintegrate in many ways, but it is guided by necessity. Its integration is a matter of necessity, and its disintegration is a matter of necessity. Thus, its integration and disintegration are not arbitrary. Things or objects necessarily integrate to form other things, and things or objects necessarily disintegrate and lose their physical form.

Zhang Zai teaches that, when it is understood that material force is always governed by the principle of change, then it can also be recognized that there is no duality between integration and disintegration, existence and non-existence, being and non-being. Non-being cannot be separated from being. Thus, non-being is not an independent reality. Zhang Zai believes in the unity of being and non-being, and is critical of the concept of emptiness in Buddhism and Taoism.

The origin of the principle of change is the Way of Heaven. When the whole universe is in a process of change, the Way (the Dao) is called the Great Harmony (chapter 1, section 1).

The principle of change is revealed by successive movements of yin and yang. The yin and yang are opposite but complementary aspects of material force. Yin is passive, yielding, cold, negative. Yang is active, firm, hot, positive. Yin corresponds to winter, yang to summer. Yin corresponds to the moon, yang to the sun. Yin corresponds to earth, yang to heaven.

Both yin and yang are necessary for the Supreme Ultimate (or ultimate reality) to be revealed. Zhang Zai regards qi (material force or cosmic energy) as this ultimate reality.

Material force can be active or passive. Yin and yang are the two modes in which material force may be integrated or disintegrated. Thus, material force has both a unitary and a dual nature. It is unitary in that it may be indivisible, ethereal, spiritual. It is dual in that it may transform itself through the interaction of yin and yang (chapter 2, section 11).

Material force may condense to form physical objects, or may dissolve into empty space. The void or empty space may become a Great Vacuity (tai xu). The Void is not a state of total emptiness or nothingness. It is the formless state of material force.

Material force may be manifested as solidity (shi) or vacuity (xu). Its form may be changed by consolidation or dispersion, contraction or expansion, movement or stability. Its transformation is caused by the movements of yin and yang.

According to Zhang Zai, human nature and destiny are caused by material force, but material force may be overcome by moral character (chapter 2, section 43). The Principle of Heaven may be achieved by moral effort, which can guide human destiny. Virtue may overcome material force. Virtue may guide human nature, as well as determine destiny.

Zhang Zai views sincerity (cheng) as a state of virtue, in which we are in unity with the Way. If we try to set ourselves apart from the Way by following our own selfish desires, we cannot achieve sincerity. Enlightenment is the state of knowledge in which we follow the Way. This knowledge transcends any empirical knowledge which we may have of the physical world.

If we are virtuous, we show kindness and respect to others, and care for the helpless and the needy. For Zhang Zai, the most important principle of ethics is ren (benevolence or humanity).

Human nature and the physical world develop from material force, which is manifested by the diversity and multiplicity of human beings and physical things. If we follow the Way of Heaven, we can understand both the unity of material force and the multiplicity of its manifestations. Zhang Zai says in The Western Inscription that: “All people are my brothers and sisters, and all things are my companions.”³ Thus, ren is a moral principle which applies to the whole universe.

¹ Carson Chang, The Development of Neo-Confucian Thought (Westport: Greenwood Press, 1957) p.171.
²Ibid., p. 171.
³Chang Tsai, "The Western Inscription," in A Source Book in Chinese Philosophy, translated by Wing-Tsit Chan (Princeton: Princeton University Press, 1963), p. 497.

Chan, Wing-Tsit, A Source Book in Chinese Philosophy, Princeton, Princeton University Press, (1963), 495-517.

Chang, Carson, The Development of Neo-Confucian Thought, Westport, Greenwood Press, (1957), 171-182.

Fung Yu-Lan, A History of Chinese Philosophy, Princeton, Princeton University Press, (1953), 477-498.

Fung Yu-Lan, A Short History of Chinese Philosophy, New York, The Macmillan Company, (1948), 278-9.