Zhu Xi made a comprehensive exposition on the concept of knowing and doing in the chapter of the University. He said: "The so-called person who knows things well, if he wants to know what I know, he will be poor in the immediate things." Its meaning is as follows:
(1) to be elegant is to exhaust the reason of things. Case means "to do" and "to". Zhu Xi believes that only when things are exhausted to ten points can they be counted as things. "Gewu" should first be widely read and heard, from personnel to nature, from heaven and earth to yin and yang, to insects and plants. Explore its laws from many things. However, it is not to exhaust all the principles of the grass and trees, but to "be poor in justice, be wise in human relations, speak holy words, and know the world" (Collected Works, Volume 39). Zhu Xi believes that if you look at the principle of everything and indulge in the knowledge of every grass and tree in nature, it is like "cooking sand and wanting it to become a meal." In his view, if you want to be poor, you must read the books of sages and achieve the highest cultivation of feudal morality, rather than knowing the laws of objective things. He regards reading, talking, treating others and doing things as "being materialistic". "If you study, you will be qualified in words; When you listen to people, you will speak well; If you pick up something, you will pick it up. Fine, thick and small must be standardized, and it will pass after a long time "("Genre 15 University "II). This is the ethicalization of Confucian epistemology.
(2) to know is to promote and expand one's knowledge to the extreme. To mean to push away and push the pole. Why is knowledge omniscient and omnipotent? In Zhu Xi's view, this is "knowledge from the heart" and "not from the outside". Because "the reason is in the heart" (Volume 5 of Genre). "The pericardium is all-encompassing, and all-encompassing is in one heart" (Volume 9 of Genre). This is the transcendentalism of idealism. He believes that the subject's understanding of the object is only the self-knowledge of "reason" itself. Therefore, the heart is omniscient, and there is no need to ask for "reason", just knowing my reason. For example, children know how to love their fathers and respect their brothers when they grow up. However, this is only "the knowledge from the heart", and it must be extended to reach the limit of knowing everything. Therefore, his theory of "knowing by observing things" is that "observing things by reasoning" and "knowing by speaking from the heart". Because the reason lies in the heart, therefore, knowing is to examine the heart, and don't let the soul of the heart be affected by people's feelings and temperament. Be blinded by material desires such as feelings. It seems that the mirror is covered with dust and no longer shines. Wipe off the dust and make the mirror reflect itself. In this way, Zhu Xi changed from objective idealism in ontology to subjective idealism in epistemology.
As a transcendentalism, of course, it is not a process from ignorance to knowledge, from little knowledge to more knowledge on the basis of practice, but a process from ignorance to being deceived and returning to knowledge. Zhu Xi compared this process to the process of waking and sleeping. He said: "People's original heart is unknown, just like those who sleep are unconscious. If they don't know about this body, they must wake up to know it ..." (Genre Volume 114) That is to say, when people sleep, knowledge and moral concepts have not disappeared, but they can't play a role for the time being; I understand everything when I wake up, and I am "smart with eyes and ears" and can "respond to things" correctly, so there will be no mistakes. This kind of wisdom, which can awaken the sleeping people, eliminate the deception and restore the talent, is very similar to the idea of "memory" in ancient Greece.
However, Zhu Xi's epistemology has reasonable factors that violate his transcendentalism. Mainly manifested in:
(1) put forward the materialistic proposition of "material poverty". He believes that "everything in the world is unreasonable" (Volume 44 of Genre), that is to say, everything has its own laws, and only when it comes into contact with objective things can we understand its laws. For example, he said that tigers are terrible or not, and only those who have been bitten know best; Whether wine can intoxicate people, whether rice can satisfy people, whether poison can kill people, etc., is only known after eating. Zhu Xi realized here that all true knowledge originated from direct experience. This is close to materialistic empiricism.
(2) put forward the dialectical proposition of "knowing and doing need each other". Philosophy, as an objective idealism of "reason comes first in qi", inevitably advocates that knowledge precedes action in epistemology, fails to understand the truth that knowledge is produced in practice and serves practice, and splits the unified view of knowledge and action. However, he thinks that action is more important than knowledge, and puts forward the important proposition of "knowing and doing should be combined". He said: knowing and doing often need each other. If you have no eyes and no feet, you can't see without eyes. On the priority, knowing is the first; On the importance, the behavior is heavy. "("Genre "Volume 9) Zhu Xi inherited the tradition of Confucius' application of what he has learned and developed the Confucian spirit of attaching importance to practice. In his view, knowing and not doing it, "sitting alone behind closed doors", puzzling over the word "enlightenment" is no good, just like having no eyes and no feet. He said: "Today, it is also necessary for monks and nuns to follow the wise men of the four sides, observe the affairs of the four sides, see the situation of mountains and rivers, and observe the gains and losses of the rise and fall of chaos in ancient and modern times. This truth can be seen everywhere. " ("Genre" Volume 117) Only when you see what you do, you will know more clearly. This view of "emphasizing behavior" and "knowing and doing should be combined" has been a dialectical thought that knowing and doing depend on each other, promote each other, and cannot be neglected, which quite exceeds the previous views and is also a great contribution in the history of China's cognition.