"Doubt without doubt, never learned; Learning requires doubt. " -Zhang Zai

Knowledge is based on facts and evidence. Knowledge is based on facts and evidence. There are two sources of facts and evidence: one is what I saw with my own eyes, and the other is what I heard from others. There are two sources of facts and evidence: one is what I saw with my own eyes, and the other is what I heard from others. For example, when there is a national crisis, there must be a lot of oral news from all over the country. How dangerous it is, it is all legends of others, which is not necessarily reliable. For example, when there is a national crisis, there must be a lot of oral news from all over the country. How dangerous it is, it is all legends of others, which is not necessarily reliable. To understand the actual situation, we must observe it by ourselves. To understand the actual situation, we must observe it by ourselves. The same is true of learning. The most important and reliable material is the factual evidence you saw with your own eyes. But sometimes such evidence can't be seen with your own eyes, and you can only rely on other people's legends. The same is true of learning. The most important and reliable material is the factual evidence you saw with your own eyes. But sometimes such evidence can't be seen with your own eyes, and you can only rely on other people's legends.

We should think about the legendary words, believe it or not, and should not believe it casually. We should think about the legendary words, believe it or not, and should not believe it casually. We believe it because it is; Don't believe it, because it's not. We believe it because it is; Don't believe it, because it's not. This kind of thinking in advance, refusing to believe casually, is the spirit of doubt and the basic condition for doing all learning. This kind of thinking in advance, refusing to believe casually, is the spirit of doubt and the basic condition for doing all learning. We heard that there were three emperors and five emperors in ancient times, so we have to ask: Who said this? We heard that there were three emperors and five emperors in ancient times, so we have to ask: Who said this? In which book did you first read it? In which book did you first read it? When was this book written? When was this book written? How did the author know? How did the author know? We also heard that "rotten grass is a firefly", so we have to ask: How can a dead plant become a flying beetle? We also heard that "rotten grass is a firefly", so we have to ask: How can a dead plant become a flying beetle? What is the scientific basis? What is the scientific basis? If we can ask this question, all wrong theories will be broken. If we can ask this question, all wrong theories will be broken.

No matter what kind of books and knowledge we have, we must first go through doubt, think because of doubt, and distinguish right from wrong because of thinking. No matter what kind of books and knowledge we have, we must first go through doubt, think because of doubt, and distinguish right from wrong because of thinking. After three steps of doubt, reflection and discrimination, that book is my book, and that kind of knowledge is my knowledge. After three steps of doubt, reflection and discrimination, that book is my book, and that kind of knowledge is my knowledge. Otherwise, it is blind superstition. Otherwise, it is blind superstition. Mencius said that "it is better to believe in books than to have no books", that is, to teach us a little skepticism, not to follow blindly and not to be superstitious. Mencius said that "it is better to believe in books than to have no books", that is, to teach us a little skepticism, not to follow blindly and not to be superstitious.

Doubt is not only a necessary step to distinguish fallacies from mistakes in negative aspects, but also a basic condition to establish new theories and obtain new inventions in positive aspects. Doubt is not only a necessary step to distinguish fallacies from mistakes in negative aspects, but also a basic condition to establish new theories and obtain new inventions in positive aspects. It is ideological laziness to admit what others say without discount. It is ideological laziness to admit what others say without discount. This mentality is always passive and can never be learned. This mentality is always passive and can never be learned. Only the brain that often doubts and asks questions has problems, and if there are problems, it wants to find answers. Only the brain that often doubts and asks questions has problems, and if there are problems, it wants to find answers. All knowledge can be improved by constantly asking questions and solving problems. Many great philosophers in universities were tempered by suspicion. All knowledge can be improved by constantly asking questions and solving problems. Many great philosophers in universities were tempered by suspicion. Dai Zhen, a great scholar in Qing Dynasty, read Zhu's Great Learning when he was young. Zhang's sentence ",he asked when" University "was written and when Zhu was alone. Dai Zhen, a great scholar in Qing Dynasty, read Zhu's Great Learning when he was young. Zhang's sentence ",he asked when" University "was written and when Zhu was alone. The teacher told him that Daxue was a book of the Zhou Dynasty and Zhu was a scholar of the Song Dynasty, so he asked the Song people how they knew the author's meaning more than a thousand years ago. The teacher told him that Daxue was a book of the Zhou Dynasty and Zhu was a scholar of the Song Dynasty, so he asked the Song people how they knew the author's meaning more than a thousand years ago. Descartes, a great French philosopher, also said, "I doubt, so I exist." "His philosophy is based on the suspicion and discrimination of everything. Descartes, a great French philosopher, also said, "I doubt, so I exist." "His philosophy is based on suspicion and discrimination against everything. All scholars, not only for folklore, but also for the theories of scholars of past dynasties, often have doubts, often argue with the theories in the book, often judge the theories in the book, and often revise the theories in the book. All scholars, not only for folklore, but also for the theories of scholars of past dynasties, often have doubts, often argue with the theories in the book, often judge the theories in the book, and often revise the theories in the book. Only in this way can we produce a newer and better theory. Only in this way can we produce a newer and better theory. Throughout the ages, new inventions in science, new theories in philosophy and new styles in art have all come from this. Throughout the ages, new inventions in science, new theories in philosophy and new styles in art have all come from this. If later scholars stick to the old saying of predecessors, there will be no new problems, no new inventions, all academics will stagnate and human culture will not progress. If later scholars stick to the old saying of predecessors, there will be no new problems, no new inventions, all academics will stagnate and human culture will not progress.