Zhang Zai and the Cheng Brothers
While Zhou Dunyi and Shao Yung were developing a system of synthesis of Confucian, Daoist, and Yin-Yang School of Thought, paving the way for a new synthesis of Confucian learning that was to be called neo-Confucian learning, three other contemporaries also contributed tremendously to the process. They were: Zhang Zai/Chang Tsai (1020-77), Cheng Hao (1032-1085), and Cheng Yi (1033-1108). The latter two were brothers and were often referred to as the Cheng brothers.
1. Zhang Zai and the concept of Qi/Chi (air, breath)
Zhang Zai's greatest contribution to the discussion of the Supreme Ultimate was his linkage of it with the idea of qi. Qi, to him, was the best characterization of the Supreme Ultimate in action because of the opposite forms it took simultaneously: rising and falling, floating and sinking, and movement and quiescence, which indicated the interactions between the yin and yang forces. (Fung, 179)
In Zhang Zai's order of things, qi did not exist completely on its own (which is one place where he differed from Mencius)Although changes varied, they followed certain rules. This is called the order of heaven (tian chi). This means outside the qi (breath), there is principle. According to the jargons of Greek philosophy, the relationship between material things and principles is that of matter and form. When matter is put in a form, it becomes a specific object. But Zhang Zai did not elaborate on this. The person who did so was Zhu Xi.
For Zhang, the idea of qi also permeated human nature. Zhang Zai was the first to discuss qizhi (temperament, character, related to qi): human nature is made up of qizhi. Human nature was the interaction between the primeval world and qi (air, breath). From the combination of human nature with the intellective and perceptive faculties is derived the term ‘mind’ (xin). Thus for Zhang Zai, human nature and human mind both came from the primeval world and were shaped by the rules governing qi. His ultimate goal was to obliterate the difference between individuals and the universe and merge them into one.
2. Cheng Hao and the integration of li (principles) and qi (breath, air)
If Zhang Zai developed the idea of qi as the material forces of yin and yang that brought about specific things in the universe, the Cheng brothers elaborated on the idea of li and its relationship to qi that broadened the discussion of the neo-Confucians. For Cheng Hao, heavenly principles could not exist independent of matter; thus li and qi were an integral whole (it is like saying you cannot discuss the form of horse and the nature of the animal called horse as separate things). Inheriting Zhang Zai's discussion of qi, Cheng Hao argued the qi in each individual constituted human nature, which was not too different from Zhang Zai's definition of human nature. And like Zhang Zai, Cheng Hao's ultimate goal was to merge individual humans with the universe. To Cheng Hao, heaven possessed the largest amount of humaneness.
3. Cheng Yi and the separation of li and qi
Even though Cheng Hao went a step ahead than Zhang Zai in bringing in the discussion of li (principles) in the discussion of changes in the world, it was his yonger brother Cheng Yi who advanced more novel arguments on the interactions between li and qi. Cheng Yi believed li and qi could be separate, similar to the Greeks’ view that knowledge and matter could be separate. Plato, influenced by Pythagoras, believed numbers were abstract and were independent of matter. Plato believed there was a world of concepts independent of the real world. Since then, the lixue (study of li) branch of the neo-Confucian school emphasized the separation of principles from matter. The lixue branch also distinguished between phenomena (xiang) and numbers (shu), separating li and qi, with qi meaning matter and li form. Matter existed within the boundary of time and space and was the essence of specific things, while form existed outside of time and space and was eternally changeless. But the school of the study of the mind (xin xue) created by Cheng Hao, did not differentiate matter and principle. Thus Cheng Hao did not pay much attention to the division between metaphysics and physics, but Cheng Yi did.
To Cheng Yi, changes in matter were due to the gathering or dispersion of the qi. The nature of things was determined by their li, although their changes were caused by changes in qi. Human nature, like the nature of other things, was determined by the li in the world, which, when realized in each individual, becomes xing (for his brother, xing comes from qi, but for Yi, it comes from li). Because individuals relied on their qi, the impure or pure qualities of qi led to qing (sentiments)Xing (human nature/temperaments) could not be seen, and was expressed only through sentiments. (imperfections of sentiments or qing, because they originated from qi, then led to imperfect manifestations of xing.) Because for him, , human nature is principle, or li, a thorough understanding of all the principles in the world would be achieved through exhaustion of the li or principles in matter, which also meant exhausting the same principles in our hearts that would lead to a full understanding of our hearts, or the heart of the universe, which are one. It was Cheng Yi's idea of li and human nature that Zhu Xi would chiefly rely on to develop the lixue branch of neo-Confucian learning to a higher stage, which exerted a tremendous influence on Chinese Confucian learning in the next 500 years.